Fuel related?

I have a 1997 Buick Lesabre Custom with 108,000 miles on it.

There are two issues I am experiencing. However, there is a story behind these problems.

Originally, the car was having trouble starting; I would have to crank the car for around 5-7 seconds before it started. That was if it started, occasionally it would fail to start on the first try.

I suspected the fuel pump, and my mechanic confirmed my suspicion. He replaced the fuel pump and all seemed well.

The other issue that I experienced before the new pump was that going up gradual hills, the car would "miss". Now when I say miss, I mean that during smooth acceleration, right around 1500 rpm, the tach would drop to 0, and I am forced to drop the pedal almost to the floor to continue accelerating. This issue never occurred on flat land or steep hills.

This issue still remained after the fuel pump was replaced. The car ran great, but there was an incident on the way home from a wedding. The car stalled 3 times, once on local roads, and twice on the highway, and after the third time, the car failed to start again.

The gauge showed I had over 1/4 of a tank left, but it turns out I was out of gas. After that incident I now ignore the gas gauge completely.

The next week, I was driving down a small hill, slowing to stop at a stop sign. Again, the car stalled. I was very angry, because I had been watching the odometer and I still had around 45 miles to go before I filled the tank.

I drifted the car to a flat spot, and it started up in a few tries. I drove straight to a gas station to fill up, and to my amazement I still had 3 gallons of gas in the tank.

I am stumped, I think that it may be the fuel sending unit or the fuel pressure regulator, but I have no means to test either of these. Is there anything else that may be causing these problems?

So far I have replaced:
spark plugs
spark plug wires
air filter
fuel filter (broke the fuel line in the process, used a repair kit from NAPA to repair)
battery
fuel pump

I have also tried using Seafoam to clean out the fuel system. That was done before I replaced the fuel pump. Also of note, before the new fuel pump I got about 16 MPG city and 21 MPG highway. After the change my mileage dropped to 18 MPG highway and 13 MPG city. All of these numbers are far below the EPA 17/27 estimates.

Any help in this matter is greatly appreciated!

Welcome to AF. So you never know how much gas you really have, it is possible on a steep hill, the fuel could uncover the pump. It seems you only have issues when low? Many things can cause both issues, you may have a bad ICM, crank sensor, the throttle body could need cleaning, the egr sticking can cause stalling. There is no way from here to pin this down.

I never know exactly how much gas I have, but by using estimates based on below-average gas mileage I can always fill it before it gets anywhere near empty.

The gauge tends to go crazy sometimes and jump between full and 1/4 left when it gets low.

Also, the "missing" issue happens on small-grade hills and happens no matter how much gas I have left.

The stalling also happens on small, mild-grade hills, and 3 gallons seems like a lot of gas for the fuel pump to get uncovered, especially on such a small hill.

I have two Lesabres. The delayed starting issue that you fixed by replacing the fuel pump sounds similar to what I am currently experiencing with one of the Buicks currently. The car has 200,000 miles on it and the fuel pressure bleeds off rapidly after shut off. It is either the check valve in the pump or possibly the fuel injectors, but I believe it is probably the pump. I have a pump to install, but have not got to it yet.

The stalling situation sounds like a similar issue I have experienced with my wife's Lesabre. You did not mention if the check engine light came on or not. If so, there could be codes to help. Our stalling issue did not result in any codes. I replaced the cam and crank sensors because they are known for stalling and no start situations. The culprit though, was the MAF sensor. If it stalls, I clean the MAF sensor with the MAF sensor cleaner spray. This stops the stalling completely for many months. Eventually, the stalling returns and I immediately clean the sensor. I should replace the sensor, but for now, the cleaning works. This was a difficult issue to resolve and I thought I had it fixed several times. I had swapped many parts between both cars to pin point the problem. There never has been a check engine light to help identify the issue.

It generally stalled on downhill, gradual grades. I could see the tach drop, it would cut out and not always die, but would often die. It would always restart immediately for us. I checked out many different items and replaced several parts. Someone on this board suggested the MAF sensor. I can't say this will reslove your stalling issue for sure, but it might be one thing you can take a look at.

I have occasionally experienced a cylinder miss and usually get a code to go along with it to indicate the miss.

I have experienced fuel gauge issue before. The sending unit in the tank had to be replaced. It is a variable resistor that reads between 0 and 240 ohms. Sometimes, when the tanks gets very low, the gauge will read completely full. I have also had to replace the gauge units in both cars with salvaged units (in the dash). The gauges would act up. The tach would jump from 0 to 600 RPMs. The speedometer would jump around from 0 to 50 when idling.

Thanks for the tips, I will have to look into the MAF sensor. The check engine light always stays off.

The car used to throw codes for random mis-fires and system too lean bank 1 but these issues were fixed by replacing the fuel pump and the spark plugs/wires.

Are there any ways to test and see if the MAF sensor is the problem? I read something about tapping it with a hammer while the car is idling, but it never stalls.

I only ask because I need to buy a special wrench to remove the MAF sensor on this vehicle due to the screws it uses.

Thanks again for the suggestions, I will have to start poking around some more.

First... If you are still having a hard time starting the car you may need to check the fuel pressure and see if it bleeds off... These cars are known to have issues with the fuel pressure regulator..

Also with the stalling going down hill, its possible that the Baffle in the tank may have been broken or dislodged allowing the fuel to run away from the fuel pump...

Keep in mind you have an 18 Gallon fuel tank... Running the tank low on fuel is very hard on the pump as the fuel is both the coolant and lubricant for the pump.... and if you have even a split second of dry run time on the pump the damage can be done..

Is it the Tach that drops to 0, or the speedo or both?

Honestly I think you may have a couple of different problems happening at the same time..

Keep in mind you have an 18 Gallon fuel tank... Running the tank low on fuel is very hard on the pump as the fuel is both the coolant and lubricant for the pump.... and if you have even a split second of dry run time on the pump the damage can be done.I agree, and it does not cost anymore to keep the tank full than it does to run it empty! I always fill up at no less than 1/2 tank! :smile:

During the "missing" issue, only the tach drops to zero. The speedo reads my speed correctly, but it does drop because I am going up the hill with no acceleration. I slow until I drop the gas pedal to the floor, allowing the car to accelerate again.

I have no problem filling the tank with plenty of gas left, as a precaution, I just have one concern. I read that gas is heavy, and as you get closer to an empty tank your mileage improves. I am always looking for ways to improve my gas mileage since it is already so poor.

I already fill the tank very early during the winter months due to the risk of getting stuck.

With the pump getting uncovered, I see your point, but 3 gallons still seems like a LOT of gas for the pump to be exposed and cause a stall. I am no professional, but 3 gallons seems to be plenty to cover the bottom of the fuel tank.

My only concern is that by running the car until it ran completely out of gas; did I cause permanent damage to the brand new fuel pump? I have no problems starting it, and when the pump was installed my mechanic said all of the pressures checked out normal. I mean it did stall 3 times before I ran out of gas totally, does that cause damage?

The starting issue disappeared with the new fuel pump, and I have since had zero problems starting the car. I am just lost as to where to turn next. The issues appear to be so intermittent that no mechanic would ever be able to diagnose them properly.

Thanks for all the suggestions!

I still think you have more than one issue..

On the Fuel Pump... Yes any dry run time will harm the pump in a hurry..

As for the Stalling and the Tach dropping to 0... If the tach will drop to 0, and then come back as you are still rolling, like a mini stall and then it goes again without you starting the car.... You may consider trying another Ignition Control Module....

My Question tho is, Does this problem only happen after the car has warmed up?

I can't say for certain the ICM is the issue but its worth a shot..

Also any 1993- Current 3800 ICM should work for you

The ICM grounding is always a suspect in these cases. The mounting plate upon which the ICM resides can corrode badly before there is any external evidence of it.

Welcome to AF. So you never know how much gas you really have, it is possible on a steep hill, the fuel could uncover the pump. It seems you only have issues when low? Many things can cause both issues, you may have a bad ICM, crank sensor, the throttle body could need cleaning, the egr sticking can cause stalling. There is no way from here to pin this down.

I agree with Shep. Classic crank position sensor problem. :grinyes:

I agree completely with everyone, this is two separate issues.

As for the fuel issue, I will just keep at least 1/4 tank of gas in the car at ALL times, and pray that I did no damage to the new fuel pump.

For the "missing" issue, I will check into the CPS and ICM. If I take it to my mechanic, is there anything he can do to diagnose these parts? There are some junkyards around, but for parts such as those I find it hard to justify randomly swapping parts, especially when I would prefer to buy new for reliability.

Just some updates on the symptoms. So far, I have noticed that the "missing" occurs on any flat ground, or hill less than about 30 degrees. I can get the car to do it almost every time, all I have to do is accelerate slowly across the 1500 - 2000 RPM range. The tach does NOT drop to zero; it actually drops to just over 1000.

When the car "misses", the engine shudders very harshly, and it normally lasts only a few seconds. After that, you can tell the engine is vibrating more than usual, but not as harshly. The tach drops to the 800-1100 RPM range, and as I push the pedal towards the floor, the RPM's don't change. When I get the pedal close to where the RPM's would normally be over 2000, the tach jumps up over to 2200-2700 RPM's and the shuddering disappears.

Still sound like the ICM or CPS?

Thanks for all the suggestions!

Ah so the tac doesn't drop to zero rpms. :runaround: That might change things in the diagnosis. In addition to the misfire condition are you still getting any stalling?

Did your mechanic run a scan with a full function odb-ii scan tool or a GM Tech 2? Weird not to have any random or fixed misfire DTCs along with a SES/CEL light if the missing is that bad.

Last question is did you look into a possible MAF sensor issue as suggested earlier? Try disconnecting it, the electrical connector and then see what it does just to rule it out. You can run with the MAF disconnected for troubleshooting purposes. The two screws that hold the MAF to the throttle body are Torx T20 tamper proof screws. You can get the tamper proof bits at any auto parts store.

I am not getting any stalling, but I am still on a fairly full tank of gas. That leads me to believe that the stalling is related to the new fuel pump, and I just have to keep over 1/4 tank of gas constantly. I will let you know if anything happens as I get closer to an empty tank.

My mechanic ran a scan before he diagnosed the fuel pump problem, but I cannot say for sure what kind of equipment he used. I will have to ask and get back to you.

In the past when I got the P0171 (system to lean) and P0300 (random misfire) I would just do the lend-a-tool at Advance and clear the codes. Nothing else would ever come up as being a problem, and I have not gotten either of those codes since the repairs. However, my mechanic did find it strange that there were times that my CEL was NOT on, but upon hooking up the scanner there was a P0171 code.

I will double check and make sure my CEL light is working the next time I am in the car, because I already have a burned out Brake idiot light.

I will also disconnect the MAF sensor and let you know what the results are. I can buy the tool to change it, if needed, but since it passed the "tap it with a screwdriver end" test I never bothered to buy the tool and try to clean it.

Thanks!

Just an update, I just tried driving the car with the MAF sensor unplugged...

The car starts right up, but immediately feels as though it wants to stall. While idling after first starting it, the engine shudders uncontrollably. Without touching the gas, the tach jumps up and down between 500-1500 RPM's. I drove it around twice, normal conditions, and it drove relatively normal once I got it out of park. At stop signs etc. the idle seems normal, no excessive shuddering like when it first started. The "missing" issue was still there, no changes.

I have since plugged the MAF sensor back in, but I am completely stumped as to what all this means. The issue with the tach jumping up and down between 500-1500 RPM's reminds me of situations before the fuel pump was replaced.

Before the new pump, the fuel system would lose pressure the longer it sat, and the pump could not provide the necessary pressure right of the bat when starting. There were many times, especially in the heat when the A/C was on, that I would barely get the car started. The tach would "jump" one time, then settle back down to a normal idle. Then I would drive it and everything would be fine. There were very rare situations where the "jumping" would continue even when I drove it, and was most irritating when in reverse. The jumping would go away after I pressed firmly on the gas pedal and floored it.

The CEL is on, but I have to stop at Advance and borrow the code reader to check the code. I will post an update, but my car has an interesting habit of clearing CEL codes on its own.

Suggestions?

My suspicions were correct. Upon plugging the MAF sensor back in, the car started fine, and immediately started to shudder uncontrollably. The RPM's were jumping, then surged to 2500 without touching the gas, and dropped back down to normal idle (700 - 1100 RPM's)

The CEL is gone, cleared itself after an ignition cycle or two before I could get the car to Advance, but everything is back to the way it was before, same problems. No ideas.

Any suggestions? I am stumped besides taking the car to a different mechanic.

My '97 Lesabre ran the same when I unplugged the MAF sensor; it chugged and idled fast and uneven. I went ahead and cleaned the MAF sensor filament with some MAF sensor spray cleaner while it was out and then reinstalled it. This did the trick, no more dying. Apparently, the filament is very sensitive to a little amount of dirt. Ours would die on a downhill grade when slowing down.

I believe the codes you mentioned, at least the P0171, could possibly be set by a MAF sensor issue. If I were you, I would clean the MAF sensor (cheap and easy). If that didn't work, I would replace the crank position sensor. I have replaced the cam and crank position sensors on both of our '97 Lesabres.

Another very good suggestion mentioned is cleaning the grounds well for the ignition control module. Might check and clean the battery ground and positive and make sure they are snug as well and any other grounds that look like they could use it.

The CEL is gone, cleared itself after an ignition cycle or two before I could get the car to Advance, but everything is back to the way it was before, same problems.Have them check for "History Codes". If you had a code and it disappeared, evidently it is stored!

Have them check for "History Codes". If you had a code and it disappeared, evidently it is stored!

:1:

The P0171 Lean Condition DTC is the one I'd look for and regardless still check the short and long term fuel trim values with a full function odb-ii scan tool. See what the values are and whether positive or negative.

A MAF could cause the P0171 DTC as will a bad pre-CAT 02 sensor or worse case a vacuum leak in the intake manifold system.

Leading to the question have the UIM plenum, UIM gasket or LIM gaskets ever been replaced?

Well, I finally had some free time. I stopped at Advance and got some MAF Cleaner and a set of TORX screwdrivers.

Let the record show, while a TORX T20 fits the screws on the MAF, it is not the right tool. The screws have a small raised circle in the middle, but the screwdriver is solid. Luckily the screws weren't too tight, and I was able to get them off with some pliers.

The MAF filaments both looked fine, but I cleaned them thoroughly. I also cleaned the electrical contacts. I reinstalled the MAF sensor using regular screws. I have not had a chance to drive the car to see if there is any difference.

While I was at Advance, I borrowed the code reader again. There was only one DTC from when I un-plugged the MAF sensor.

P0102 - MAF or VAF A circuit low input

I also got the freeze data before I cleared the code:

Throttle position - 0.0%
Engine RPM - 949 RM
Load value - 0.7%
Air flow rate - 1.78 GR/Sec
MAP sensor - 65 KPA
Coolant temp - 120 F
Short term fuel trim1 - +.8%
Long term fuel trim1 - +2.3%
Short term fuel trim3 - -96.7%
Long term fuel trim3 - -18.8%
Vehicle speed - 0 MPH
Fuel system 1 - OPEN
Fuel system 2 - N/A

I am definitely not an expert, but the numbers that immediately caught my attention were the short/long term fuel trim3.

I have not replaced any gaskets. I have not owned the car long, but I do have the service records and I can check to be sure.

I still have to clean the grounds on the ICM, but the battery terminals were fine. I am not going to start swapping parts without knowing what the problem is. If I take the car to a mechanic, will they have a better diagnostic tool that will reveal more information?

Thanks for all the suggestions; I am not giving up yet!

Update: The "missing" problem still exists. Any difference is just from the placebo effect because it is still happening just as it did before.

The next item on my list is to clean the throttle body. Is it best to just buy throttle body cleaner and do the work by hand, or buy Seafoam and use that instead?

It will be my first time doing either of these; does anyone have any personal experience with cleaning the throttle body or adding Seafoam to a Lesabre? I have the Haynes repair manual, but it is the generic 1985-1999 GM manual and does not even mention the throttle body location (that I can find).

If I do go the Seafoam route, is it possible for me to just split a can 50/50 between the fuel tank and the vacuum lines? If I add it to the vacuum lines, am I still supposed to change my oil right away?

I wouldn't mind trying the Seafoam, my only concern is I just changed my oil/filter less than 1,000 miles ago and I have no desire to change it already. The directions are unclear if going through the vacuum lines means you still need to change the oil.

I dumped 2 cans of Seafoam in my fuel tank a few months ago before I changed the fuel pump, it couldn't hurt to put some more through with the new pump.

Thanks for all the help!

I dumped 2 cans of Seafoam in my fuel tank a few months ago before I changed the fuel pump, it couldn't hurt to put some more through with the new pump.



:yikes:

Two cans of Seafoam??? Way too much. All you need is 1 oz per gallon. A can of Seafoam Engine Treatment is 16 oz (One Pint) so if you used two cans you dumped 32 oz into the gas tank. :nono:

Seafoam is good stuff for its intended purpose but it is not a miracle cure all for an actual problem that must be physically resolved.

Well, I knew 2 cans was overkill, but at the time I was trying to avoid what ended up being a $250 fuel pump replacement. $12.00 was a bargain, and I had read that too much can't do any harm when added in the fuel tank.

The more I read, the more I think it would be better to just clean the throttle body by hand. Opinions?

EDIT: If it helps, the "missing" issue always occurs regardless of outside temperature or run-time. The condition always gets worse when the A/C or heater is running, and seems to be the worst when the fans are on high.

Running the Seafoam into the throttle body vacuum lines or any vacuum line at the upper intake manifold (UIM plenum) will most likely be ineffective. Depending on your mileage there will be lots of carbon buildup in the throttle body especially the throttle butterfly plate, the inside of the UIM plenum and the port runner insert in the UIM plenum. See pic. Nothing beats removing the parts and cleaning them up with a suitable cleaner by hand.

Have you run an engine vacuum check?

http://i5.photobucket.com/albums/y186/lizzywiz/DSC02567.jpg

No engine vacuum check. Do I need any special tools to perform such a test?

None of the mentioned parts have ever been cleaned, and the car has 108,000 miles on it.

I am a do-it-yourself kind of person, but all of the how-to's for cleaning the throttle body just involved removing all of the hoses and cleaning it in-place with throttle body cleaner and a toothbrush.

See: http://www.popularmechanics.com/how_to_central/automotive/1272341.html?page=1

Do you think that will suffice, or should I just let a mechanic handle it? That picture looks a little involved too involved for me.

No engine vacuum check. Do I need any special tools to perform such a test?

You can use a standard automotive vacuum gauge - 0-30 in-hg. Look for a vacuum reading in range of 15-22 in-hg at idle and then taking the rpms up to around 2K and steady. A typical reading at idle with no intake vacuum issues with A/C off is around 18-19 in-hg and with A/C on approximately 17 in-hg. You can tee in at the vacuum port at the throttle body that feeds the fuel pressure regulator/purge solenoid or at the rear of the UIM plenum that feeds accessory vacuum to the HVAC system.

BTW - Make sure the engine is fully warmed up before testing.

Update: The "missing" problem still exists. Any difference is just from the placebo effect because it is still happening just as it did before.

The next item on my list is to clean the throttle body. Is it best to just buy throttle body cleaner and do the work by hand, or buy Seafoam and use that instead?

It will be my first time doing either of these; does anyone have any personal experience with cleaning the throttle body or adding Seafoam to a Lesabre? I have the Haynes repair manual, but it is the generic 1985-1999 GM manual and does not even mention the throttle body location (that I can find).

If I do go the Seafoam route, is it possible for me to just split a can 50/50 between the fuel tank and the vacuum lines? If I add it to the vacuum lines, am I still supposed to change my oil right away?

I wouldn't mind trying the Seafoam, my only concern is I just changed my oil/filter less than 1,000 miles ago and I have no desire to change it already. The directions are unclear if going through the vacuum lines means you still need to change the oil.

I dumped 2 cans of Seafoam in my fuel tank a few months ago before I changed the fuel pump, it couldn't hurt to put some more through with the new pump.

Thanks for all the help!


The reason for cleaning the throttle body is to remove the MAF and clean it while off as well as remove the IAC and clean it. The throttle body collects a gel that's black goop that deposites inside the UIM and in the throttle body metal and blocks the throttle blade from having the bleed air go around it. Often the throttle plate sticks after the car has been cool and you go to move the accelerator the first time because it's rubbing in the gel material.

Putting in a cleaner through the vacuum hoses does not clean the gel from the metal area of the throttle body. Only air moves through there and the vacuum lines come into the air flow after the metal portion of the throttle body. I've seen a guide for removing and cleaning. It's relatively easy. On my 98 the brace piece underneath has one of three screws holding the throttle body to the UIM. It's difficult to get to but the brace can be bumped and pivoted sideways to get the screw loosened and off.

I have decided (thanks to your input) that Seafoam is not an option, and that I will just clean the throttle body.

UIM - Upper Intake Manifold?
IAC - Idle Air Control?

I am do-it-yourselfer but a lot of these terms are new to me. Do you have a link to a guide that you recommend? So far the only guide I found is this one:

http://www.popularmechanics.com/how_...41.html?page=1

If I can't find anything more detailed, I am a little hesitant to take the throttle body off completely. If you know of something better, that would be great; I would far prefer to do the job properly the first time around.

I will be stopping at Advance later to buy a vacuum gauge for $20.00. While reading about the throttle body, it says that when removed I am supposed to change a gasket that it uses. What is this gasket called? That way I can pick one up as well.

I already have throttle body cleaner, and I have the Haynes service manual, but you know how generic the steps are, nothing is very specific.

I mentioned earlier that the TORX T20 screws on the MAF were not regular TORX, but required a bored out center. Will the throttle body have the same screws? I still don't have the correct tool, and I will most likely not be able to squeeze pliers into tight places.

I am still surprised that there is not a more obvious problem. I thought with fuel trim values that out of whack, the problem would be a lot easier to determine. I read somewhere that the only things to change the fuel trim values are the oxygen sensors and the MAF sensor. Could the problem just be one of the oxygen sensors being bad? My mechanic suggested that may be the problem before he changed the fuel pump, but I am not sure if he ever checked them or not.

Thanks for the suggestions!

I mentioned earlier that the TORX T20 screws on the MAF were not regular TORX, but required a bored out center. Will the throttle body have the same screws? I still don't have the correct tool, and I will most likely not be able to squeeze pliers into tight places.
You need to pick up a "security bit set". Click Here (http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=93388)for a cheap set.
I am still surprised that there is not a more obvious problem. I thought with fuel trim values that out of whack, the problem would be a lot easier to determine. I read somewhere that the only things to change the fuel trim values are the oxygen sensors and the MAF sensor. Could the problem just be one of the oxygen sensors being bad? My mechanic suggested that may be the problem before he changed the fuel pump, but I am not sure if he ever checked them or not.
I noticed in your "freeze data", it shows the coolant temp @ 120 F when you checked it. More than likely you were in "open-loop" at that temp, so therefore, the 02 sensor would not be controlling fuel trims. You can disregard anything you see there, unless the engine control is in closed- loop!

The following link discusses the fuel trim values, and from what I understand, even in open-loop mode, it still uses history data from the O2 sensors. I am not sure if this applies for all OBDII enabled cars or just this specific Toyota.

http://www.4x4wire.com/toyota/4Runner/tech/OBDII_ECU/ (http://www.4x4wire.com/toyota/4Runner/tech/OBDII_ECU/)

I will be stopping after work to pick up a security bit set, and possibly a vacuum gauge. They have the following gauge in stock, when I read the description it appears to work for both the engine vacuum and the fuel lines. Is this true or is it simply a fuel pressure gauge?

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=93547 (http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=93547)

Thanks for the tip!

IIRC, Buick uses predetermined values during open-loop operation, not an average of "history data". You can get a used MAF sensor from a bone yard if you want to try that. Click Here (http://www.automotiveforums.com/vbulletin/showthread.php?t=916619) for some more info on the MAF.

I picked up a fuel pressure gauge/vacuum gauge and the 100 security set of bits (good to have in the future).

This is the gauge I got:
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=93547

I have yet to check the fuel pressure, but I found the gauge access on the front of the engine along the fuel line for the injectors. I tested the vacuum pressure, but I am not positive I did it right.

The directions said to tap the line as close to the intake manifold as possible. According to the sticker diagram under the hood, on the back of the engine the brake booster line hits the intake manifold and right at the same spot there is a cable labeled accessory. The Haynes service manual I have said that the readings will be inaccurate if anything is disconnected during a vacuum test.

The kit included a "T" adapter, but it only came with one hose. The accessory hose I disconnected had a big plug on the end, and I could see no way to keep it connected using the parts I had.

I went ahead and tested it anyway. Here are the results (if they are any good)

Idle: Steady 23 IN/Hg with no jumping/moving
2000 RPM: Steady 25 IN/Hg and jumps to 28~30 IN/Hg on release of gas pedal

I also attempted to remove the throttle body, but I got stuck about halfway through. I got the air box out, the MAF out, the TPS off, and the first screw on the throttle body. However, I could not for the life of me figure out how to get the accelerator cable disconnected. Plus there appeared to be two cables (cruise control?) and neither would come off. The directions in my Haynes manual were FAR too generic.

I went ahead and ordered a Chilton manual used from Amazon, but it will not be here for about a week. I am going to have more time this weekend to try the work again.

Any comments/suggestions are GREATLY appreciated, thanks for all the help so far!

IIRC, Buick uses predetermined values during open-loop operation, not an average of "history data". You can get a used MAF sensor from a bone yard if you want to try that. Click Here (http://www.automotiveforums.com/vbulletin/showthread.php?t=916619) for some more info on the MAF.

LOL!
Here I am searching for more info on the IAC valve, and cleaning the throttle body, and I get led to my recent thread.
I'm exploring all options along with replacing my MAF sensor.
The Buick service manual points to a faulty or dirty IAC valve as one cause of a hard start condition.
It sounds to like removing and cleaning the throttle body is just good periodical maintenance.

:thumbsup:

Hmm. edit button isn't working for me.

Question,
Once the throttle body and all sensors are removed, can the throttle body be dunked and soaked in carb cleaner? I have one of those pails of cleaner with the basket for dunking carb parts.



:popcorn:

Earlier this week when I had the TPS off, I hooked it back up the wrong way. When I started the car, it immediately began to idle at 4000 RPM's and the check engine light came on. I fixed the problem, and eventually the light went off.

Today I stopped at Advance, just out of curiosity, and here are my numbers:

P0122 TPS/Pedal position sensor A circuit low input

Throttle Position - 0.0%
Engine RPM - 2730 RPM
Load Value - 10.9%
Air flow rate -19.17 GR/Sec
MAP Sensor - 32 KPA
Short term fuel trim 1 - + .8%
Long term fuel trim 1 - +.8%
Short term fuel trim 3 - -96.7%
Long term fuel trim 3 - +8.5%
Vehicle speed - 0 MPH
Fuel system 1 - OPEN
Fuel system 2 - N/A

The first thing I notice is there was no coolant temp listed; I am not sure if I missed it or is it possible for it to be missing?

The other thing I noticed was again the fuel trim 3 values, the short term is the same but the long term went positive somehow.

What does any of this mean? I will try again with the throttle body tomorrow; I just hope I can get the accelerator cable off. I will also try to post the fuel pressure test results as well.

Thanks!

Question,
Once the throttle body and all sensors are removed, can the throttle body be dunked and soaked in carb cleaner? I have one of those pails of cleaner with the basket for dunking carb parts.

You should not use carb cleaner on a throttle body. Use the special throttle body spray cleaner found at the auto parts stores. I would be careful soaking the TB in any solvent or parts cleaner that is too strong. There are end seals (two) located at the butterfly plate and you do not want to damage them or induce a vacuum leak.

Well, I have officially given up.

Checked fuel pressure, 50 PSI pre-start and 41 PSI at idle

Checked vacuum pressure, 18 Hg/IN at idle, 21 Hg/IN at 2000 RPM

Attempted to remove throttle body, but it is physically impossible to get the third screw off without removing a huge exhaust pipe

Checked IAC, MAF sensor, and IAT

Car still "misses" consistently going up hills.

My mileage is back up to where it used to be (16 MPG) and I didn't change anything besides cleaning the MAF

On a "low" tank of gas, I could get the car to consistently stall going down hills. It seems that when the car is in drive, I have a very low idle (~500 RPM) and upon coming to a complete stop going DOWN any hill, the car stalls.

Sometimes it starts right back up, without moving, and other times I am forced to drift it onto flat land. After playing around with the stalling, I filled the tank completely and it only took 13.3 gallons. My capacity is 18 gallons.

I guess I will just have to keep filling my tank around 10 gallons used. I mean, I am no expert, but 4.5 gallons of gas seems like a LOT of gas for the car to be stalling on hills.

Thanks for all the help; any final suggestions would be greatly appreciated. I don't want to give up, but I am officially out of ideas.

I may have missed this info. I was re-reviewing the postings. Does it miss and stall only when the engine is warmed up? How does it run on the up hill grade when the car is completely cold, right after start up? Does it miss just like when it is warmed up? Also, when it is completely cold, going down hill, does it die when coming to a stop?

I have been recently encountering a hard start issue on my 97. Later on (last week) it began to idle very high (when cold) on occasion and then, when hot, on the way home, it would idle way low (just barely stay running). I had no codes. It turned out to be the idle air control valve. Just replaced it yesterday. No more hard starts or inconsistent idling. It never set a code.

It is difficult to find the possible problem if it will not generate a code and some items will not. Have you had the P0171 return at all? I am unsure if the crank position sensor will actually set a code always-possibly not. Also, not sure if a crank position sensor would only cause the issue on slopes (likely not).Someone else may know for sure. I know the MAF sensor can create stalling on slopes and not set a code. I have encountered that issue. My wife's Lesabre would die when coming to a stop on a downhill grade. Sometimes it would die without coming to a stop-just had to be on a downhill grade.

I tend to believe it has nothing to do with the fuel level in the tank. The fuel pressure is good. It seems more electrical, but finding the electical component that will cause the problem (on hills) and not set a code is key.

I know it has been a while, but here is an update.

The "missing" issue on hills seems more prominent once the vehicle has warmed up. Also, it seems that the higher outside temperature makes it happen more often. In addition, running the A/C in the hot weather makes it even more noticeable. The stalling on a low tank of gas happens regardless of running time or outside temperature. I can pretty much get it to do it every time on any form of downward slope.

The car went to a local mechanic, who drove the car and could not reproduce any of the issues. He had no way of diagnosing the problem and told me to wait until it worsens/becomes consistent.

The car went on a highway trip, and the CEL came on, so we took it to the family mechanic. He hooked it up and he did not recognize the code. I failed to write it down (I know, I know).

I changed both O2 sensors with BOSCH OE replacements as well as the PCV valve.

A few nights ago I had the car parked on a hill for a few hours, and when I came out to leave, it refused to start. The car didn't even sound like it was cranking, but all the lights worked. I attempted to jump it, no luck. I was giving up and I wanted to drift it off the road onto some flat land to get it out of the way. I tried to start it on the level ground, just for fun, and it started right up, no hesitation whatsoever. I took it straight to a gas station and it only took a little over 11 gallons of gas, which means it still had around 7 gallons remaining.

Does anyone have any other ideas? Also, does anyone have any detailed instructions for removing the throttle body on my car? Neither the Haynes nor the Chilton manuals I have explain how to properly remove all the screws. I still have the cleaner, and I want to try using it, but I have been unsuccessful so far.

The RPM's always drop far below 1000 (~500) when I am slowing for a stop sign or coming to a complete stop. When I shift the car into neutral at a stop, the RPM's rise up closer to 1000. Is that normal?

I am still open to all and any ideas, but I honestly do not want to throw parts at the problem, I have done enough of that already. If I take the car to a dealer, will they be able to diagnose the problem without replacing any parts? How much would they charge?

Neither mechanic I took the car to so far said they had any way of reading live sensor output. Is that normal, or are they just missing equipment?

Thanks for all the suggestions so far!