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1999 Grand Prix chugs going up hills


steve53502
12-28-2004, 06:11 PM
My wife's 1999 Grand Prix GT 3.8 chugs when under load like when you go up a steep hill or sometimes when you get on it. She had me drive it and when it started to chug I got on it and then the check engine light came on. Any ideas???
Thanks, Steve

drjimmy
12-30-2004, 11:32 AM
does the chugging go away when you lightly press the brake?

MIGTPGUY
12-30-2004, 11:43 AM
hard to say, has to be a liquid not circulating properly due to being unlevel.

drjimmy
12-30-2004, 01:52 PM
It is not always the tranny. One guy had that problem and it turned out to be intake gasket. Mine is doing that too but when I press on the brake it stops chugging which means it is related to the lock up converter. When I get my scanner, I'm going to find out if the computer is telling the lock-up converter to engage/disengage or if it is in the tranny.

steve53502
12-31-2004, 03:37 PM
It has not done it again since I replaced the plugs and wires so my wife has not had a chance to try out the brake trick. Still I doubt that plugs and wires were the problem. I had a Sunbird that the lock up went out on and I ended up just disconnecting the wires to it. Do you think that could be the problem with this?
Thanks, Steve

wylie
01-14-2005, 06:34 PM
drjimmy: My grand prix 1999 does the same thing have you found a fix for it yet?
I just touch the brakes and it goes away.

highspl
01-14-2005, 08:28 PM
A long time ago that happend to me on a 92 buick century, changed the plugs and wires and it was fine after that!

fast6
01-15-2005, 07:15 PM
same problem on my 99 grand prix. Bad plug wire.

wylie
01-16-2005, 12:17 PM
Quote: same problem on my 99 grand prix. Bad plug wire.

I've had it on a scope twice wouldn't this show up?

And I don't understand the tap the brake lightly and it goes away part.
the car 1999GPT runs fine most the time until its under load(going up Hills mostly) and it starts, if you touch the brake light or hammer down on the gas its goes away.
The PO is that I've had it in twice and they tell me nothings wrong.
Whats a good set of wires to use? Last time I did wires on my older GP the mechanic told me not to use wire made by Cheap Charlie.

sonya1805
01-17-2005, 01:25 PM
It has not done it again since I replaced the plugs and wires so my wife has not had a chance to try out the brake trick. Still I doubt that plugs and wires were the problem. I had a Sunbird that the lock up went out on and I ended up just disconnecting the wires to it. Do you think that could be the problem with this?
Thanks, Steve
What engine is in it? Mine is a 3.1 Only acts up when going up hill as if it's the fuel pump but isn't the fuel pump. Hooked it up to the fuel pressure gauge & it's giving the right reading of pressure. I am stumped.

steve53502
01-17-2005, 03:40 PM
The motor in our car was the 3.8 (not super charged). It has not done it again since I replaced the plugs and wires. As far as the brake tap thing goes, maybe it has something to do with the torque converter lock up solenoid ???

gr8on8
01-17-2005, 10:07 PM
i have recently bought a 99 grandprix and it tends to chug going uphill but it also does it going down the road at around 2000 to 2750 rpm, changed plugs and wires and it did not help, i think mine is fuel related some throtle sensor, but not shure any ideas would be nice

troy1
01-17-2005, 10:15 PM
dont say the tranny is bad before you completely rule out a engine miss tapping the brake is unlocking the torque converter and letting the engine miss be absorbed. when the torque converter is locked up its like having a solid connection every engine miss will be felt

Ripn12s
01-17-2005, 10:44 PM
Probably just the torque convertor. When going up hills the convertor probably starts out locked and then when you give it just enough gas to get up the hill its locking/unlocking.

Surprised no one has said to go get the car scanned. If it threw a SES then go find out what code it is.

gr8on8
01-18-2005, 08:05 AM
my cars service light or check engine light has not come on but because i have only owned it for 18 days i might check it and c if it went off before i bought it. i will check out the torque converter

drjimmy
01-18-2005, 10:15 AM
I'm still getting around to getting my scanner put together but I suspect it is something in the engine causing mine to chug. I tried new wires a few months ago but it didn't help. I did not get any codes either on my code reader and my ses light never came on. I suspect that the TCC is being requested by the computer and then being told to unlock due to low vaccum or something cause it only happens under load. Won't know for sure until I scan it while it is happening. I feel the TCC is fine cause it is locked before I go up the hill.

gr8on8
01-18-2005, 11:45 AM
drjimmy when you find out could you let me know sounds alot like my problem thanks

wylie
01-19-2005, 09:14 PM
I'm still getting around to getting my scanner put together but I suspect it is something in the engine causing mine to chug. I tried new wires a few months ago but it didn't help. I did not get any codes either on my code reader and my ses light never came on. I suspect that the TCC is being requested by the computer and then being told to unlock due to low vaccum or something cause it only happens under load. Won't know for sure until I scan it while it is happening. I feel the TCC is fine cause it is locked before I go up the hill.
Wow Thanx: drjimmy:
Hey I'm new here I like it.
I've thrown cash at this already I hate it,bin on the scope twice,I've got the wires its still happening.
This is my second GP I wanted to keep this one.
drjimmy: If you figure this out your my hero.

wylie
01-23-2005, 11:02 AM
I really hope someone can come up with an answer, seams to be allot here with the same problem.
I've had mine scanned twice once a the dealer and they say nothings wrong with it.
So I guess we're all just imagining the same thing.

BNaylor
01-23-2005, 12:25 PM
I had a similar problem with my 1999 Buick Regal with the Series II 3800 engine. At 50,000 miles during the cooler months of the year it would chug or buck going up a hill or incline. If I let off the gas and then stomped the accelerator, the problem would disappear. It was intermittent and would disappear in the warmer months. No SES or Check Engine light ever came on.The local dealer was of no help or use.

At approximately 90,000 miles and two years later, the problem developed into a stall or miss at low rpms or a dead spot/miss during acceleration at high rpms. The SES light came on. Again the problem was intermittent but very annoying.

I replaced the spark plugs, wires, air filter, fuel filter, pcv valve, checked for bad fuel, etc. Still had the same problem.

I took it to an Autozone where they put a handheld ODB-II Code reader
on it. It showed a MAF Sensor DTC error code. The MAF sensor on the 3800 is located on the throttle body (top) right after the air cleaner inlet. It is used for timing, fuel injector control and load reference to the automatic transmission via the ECM and Powertrain module.

For troubleshooting, you can disconnect the electrical connector on the MAF and see if the problem disappears. The SES light will either illuminate or stay on but the car will run fine because the ECM will force the car into limp home mode and reference to RPMs instead of directly off the MAF sensor. Another sign of a defective MAF is the transmission may shift hard or you may hear a high pitched whining sound in all gear positions.

I replaced the MAF with one from a salvaged Regal for $35.00. There are two Torx safety screws that hold it in place. Cleaning the sensor wire elements made no difference and should not be done because the air flow wires could break. The final step after replacement is to disconnect the battery positive cable and then turn your ignition (hold) to the on position for at least 1 minute and release. Connect the battery cable and then turn the key to the off position. This procedure will extinguish the SES light. Start the vehicle and everything should work fine and the SES light should be off. Next be sure to take it out for a spin and let the ECM relearn.

The car now works like a champ and the performance feels like the day I bought it. Hope the info helps you and others with a similar problem. Good luck.

gr8on8
01-26-2005, 09:22 AM
bnaylor3400 thanks for that info. after reading that i went out and unplugged my maf and shure enough thats whats wrong with my car, cant find a salvaged one so i had to buy one with a price of 138.88 thanks and i hope others get it fixed

wylie
01-26-2005, 10:26 AM
bnaylor3400 thanks for that info. after reading that i went out and unplugged my maf and shure enough thats whats wrong with my car, cant find a salvaged one so i had to buy one with a price of 138.88 thanks and i hope others get it fixed
I'll Second that,Thanx bnaylor3400:This has been ongoing for a couple of years now it sure will be nice to have it fixed.
Hey your your ever in Toronto Look me up,my sister will be your friend.

DarkTint
01-27-2005, 04:08 PM
I'm having the same annoying problem, and that is AWSOME info. Thank you!

Now the real question: Will the dealership fix this under my extended warranty??? :uhoh:

drjimmy
01-27-2005, 06:34 PM
bnaylor3400 thanks for that info. after reading that i went out and unplugged my maf and shure enough thats whats wrong with my car, cant find a salvaged one so i had to buy one with a price of 138.88 thanks and i hope others get it fixed

Okay, before we break out the champagne, keep in mind what our problem is and what the symptoms are. The symptom is our car "chugs" because the lockup is engaging and disengaging while under load. The problem could be a host of other things. Unpluging the Maf sensor does not give us an indication of the problem because you are just taking the computer out of closed loop. This keeps the computer from engaging the lockup converter and yes the symptom goes away. But the problem is still there.

If I unplug my O2 sensor or temp sensor or any other sensor that is needed for closed loop, I will get an SES light and the car won't chug cause I aint in closed loop. The car will only chug when the computer is only in closed loop. You probably notice the chugging doesn't occur until the engine is at operating tempature (also a condition of closed loop).

I'm not trying to be argumentative here and I appreciate the info about the MAF sensor. I'm just pointing out that there probably isn't a one thing cure all solution here.

gr8on8
01-27-2005, 10:25 PM
i have tested my car odb tester and it says that it is the MAF sensor so i still like the theory but it does make me wonder what else it is but i know that part is bad so i will replace it if it still does it i will go on and figure it out but i think it might only be tha MAF i will know more when i get the part tommorrow.

BNaylor
01-28-2005, 01:24 AM
Okay, before we break out the champagne, keep in mind what our problem is and what the symptoms are. The symptom is our car "chugs" because the lockup is engaging and disengaging while under load. The problem could be a host of other things. Unpluging the Maf sensor does not give us an indication of the problem because you are just taking the computer out of closed loop. This keeps the computer from engaging the lockup converter and yes the symptom goes away. But the problem is still there.

If I unplug my O2 sensor or temp sensor or any other sensor that is needed for closed loop, I will get an SES light and the car won't chug cause I aint in closed loop. The car will only chug when the computer is only in closed loop. You probably notice the chugging doesn't occur until the engine is at operating tempature (also a condition of closed loop).

I'm not trying to be argumentative here and I appreciate the info about the MAF sensor. I'm just pointing out that there probably isn't a one thing cure all solution here.
************************************************** **
Reply:
The GM OBD-II Compliant EFI/Emissions system is based on two modes of operation: open and closed. It uses closed loop when conditions are "ideal" such as at idle when fully warmed up or at cruising speeds.
Feedback to control the fuel injectors comes primarily from the O2 sensor, etc. In other words controls catalytic convertor feed-gas content by keeping the air-fuel mixture modulated around the "ideal ratio"

It goes to closed loop mode when the engine is under a load such as going up a hill or accelerating, etc. IE: During conditions that require air-fuel mixture richer or leaner than "ideal", the system disregards the O2 sensor signal and controls injection duration based on other sensor inputs such as the MAF (Mass Airflow) and MAP (Manifold Absolute Pressure), etc.

Unplugging the O2 sensor doesn't prove anything because it is a closed loop component. The "chug" is occuring because the engine is under a load condition and in the open loop mode, therefore, troubleshooting sensors used in open loop mode only would seem more logical and relevant. Hence, disconnecting or replacing the MAF sensor makes more sense.

The bottom line is replacement of the MAF sensor corrected my problem
and the diagnostic system correctly gave a DTC code of defective MAF sensor accordingly. No more chug, misfire or SES light. Replacement of the MAF sensor for $35 - $135.00 beats going insane over the problem.

Good luck!

drjimmy
01-28-2005, 09:23 AM
I don't doubt that it was your problem. I'm only saying that it might not be everyones problem. Especially if you got a code telling you that the MAF is bad. (my code reader says everything is fine. That's what is so annoying)

Are you saying that the lock up converter will lock if the Maf is unplugged? Cause if it does I will try it.

gr8on8
01-29-2005, 11:10 AM
i replaced it and it works great just like new and no codes show up anymore so the problem is fixed on my car. thanks for the help

BNaylor
01-29-2005, 05:50 PM
i replaced it and it works great just like new and no codes show up anymore so the problem is fixed on my car. thanks for the help

You're welcome. Glad the info helped and probably saved you a lot of money. My Regal has been running like a champ for over 30 days now since I replaced the MAF sensor.

BNaylor
01-29-2005, 06:23 PM
I don't doubt that it was your problem. I'm only saying that it might not be everyones problem. Especially if you got a code telling you that the MAF is bad. (my code reader says everything is fine. That's what is so annoying)

Are you saying that the lock up converter will lock if the Maf is unplugged? Cause if it does I will try it.
************************************************** ****

I don't purport to be an expert but just sharing my specific instance with a very similar problem. In my case I went two years with the nagging problem until I lucked out one day and the MAF sensor DTC showed up. Initially, I didn't even have a SES check engine light but it would chug going up a hill under load. The dealer was dumbfounded and stated that they could not fix anything that did not appear to be broken since there were no DTC codes or SES light.

I talked to a GM Mr. Goodwrench master mechanic and he said that the torque convertor will operate properly with a defective MAF sensor or even one disconnected for troubleshooting purposes. Instead of using air flow from the MAF sensor the ECM/PCM switches to pre-programmed values for RPM. Thats why your car should run fine even without the MAF connected. The SES light will stay on. Normally, all you will get with it disconnected is an erratic idle for a few minutes but the car will operate normally although you may lose a few miles per gallon until a new sensor is installed. The torque convertor locks only in the closed loop mode and when in overdrive. If going up a hill, accelerating, decelerating, etc. the ECM/PCM switches to open loop mode and the torque convertor is supposed to be inhibited.

You may have more than one problem if your Grand Prix's torque convertor is not locking up under the "ideal" circumstances. The speed sensor provides info to the PCM/PCM to control the convertor, so it could be defective. You may have a vacuum leak at the intake manifold or a flaky throttle position sensor.

However, a defective MAF may affect the transmission. It may shift rough or have a whining sound, intermittently, which appears to be the torque convertor staying locked up.

Forum member gr8on8 had the same problem and replacing the MAF fixed his problem too.

I'd recommend replacing the MAF sensor just to be sure. Good luck!

nexteldone
01-31-2005, 01:24 AM
i bought a 94 GTP with a 3.4 engine after the car warmed up , the car would lag under load, ended up replacing 2 coils , and it fixed the problem

jon95se
01-31-2005, 01:34 AM
change your fuel filter. after that, other cause could be, o2 sensor, or need of a tuneup

drjimmy
01-31-2005, 07:19 PM
Well I'm man enough to admit when I'm wrong. The TCC will lock if you unplug the MAF. Unfortunately it still chugs when I unplug it. Still looking.......

es3153
03-23-2005, 12:25 AM
I've had the same problem fro a long time and it is so aggrivating. the dealer and my mechanic can't locate the problem, but they were more than happy to change out the coil packs, plugs, plug wires and everything else they could think of, even though I had just changed a bunch of that stuff out myself, and the fuel filter. A buddy has a 1999 GP SE also wth the same problem, and he said it was a transmission problem, but I am not buying it 100%.

I am going to try the MAF and see what happens.

Now all I need is to fix that dreaded clock light.............

BNaylor
03-23-2005, 08:48 AM
I've had the same problem fro a long time and it is so aggrivating. the dealer and my mechanic can't locate the problem, but they were more than happy to change out the coil packs, plugs, plug wires and everything else they could think of, even though I had just changed a bunch of that stuff out myself, and the fuel filter. A buddy has a 1999 GP SE also wth the same problem, and he said it was a transmission problem, but I am not buying it 100%.

I am going to try the MAF and see what happens.

Now all I need is to fix that dreaded clock light.............


It doesn't hurt to try the MAF and won't cost anything initially. All you have to do is disconnect it and test the car again. The idle may be a little erratic until the engine is warmed up. At least you can rule it out.

What size engine do you have in your GP SE? Another note: If you changed out the plugs and wires make sure they are proper for your model. Stick with the AC Delco Rapidfire or Iridium spark plugs and GM Packard 7mm wires if your car is stock. Cheapy aftermarket wires and plugs may give you the same problem (the chug).

99grandgt
03-25-2005, 01:27 PM
i have a 99 gt, 3800 in it, and replaced the coils, wires, and plugs. it ran hella fast compared to stock pieces. i put 45,000 volt dis coils from accel on it, and i was wondering, since i gapped the tr55 ngk plugs at .060, like the book says, is that too much electricity lighting off that fuel charge, causing the o2 to read a leanout condition and mess up the drivability? there arent any other problems that i can think of with the car. has uncer 70k miles. even accel is stumped.... (crappy 7mm oem replacement wires, waiting on the taylors, those ngk plugs, and accel coil pack...put stock coils back on it) any suggestions?

es3153
03-26-2005, 04:11 PM
It doesn't hurt to try the MAF and won't cost anything initially. All you have to do is disconnect it and test the car again. The idle may be a little erratic until the engine is warmed up. At least you can rule it out.

What size engine do you have in your GP SE? Another note: If you changed out the plugs and wires make sure they are proper for your model. Stick with the AC Delco Rapidfire or Iridium spark plugs and GM Packard 7mm wires if your car is stock. Cheapy aftermarket wires and plugs may give you the same problem (the chug).

My engine is the 3.1. I changed out the plugs and wires first, put in Platnium Bosch Split-fire-type. Still ahd the problem. Then my mechanic basically said the same thing you said above, so he switched them back, as well as a "bad" coil pack, still the same thing. I don't normally go cheapy, if I can help it.

Were you the one that had the links to changing the stock radio light? Mine is starting to go into the "flick" mode, where I have to flick it with my index finger to get it to come one. It then filckers like a bad element.
BTW, will a bad MAF also affect fuel economy?

BNaylor
03-28-2005, 12:54 PM
My engine is the 3.1. I changed out the plugs and wires first, put in Platnium Bosch Split-fire-type. Still ahd the problem. Then my mechanic basically said the same thing you said above, so he switched them back, as well as a "bad" coil pack, still the same thing. I don't normally go cheapy, if I can help it.

Were you the one that had the links to changing the stock radio light? Mine is starting to go into the "flick" mode, where I have to flick it with my index finger to get it to come one. It then filckers like a bad element.
BTW, will a bad MAF also affect fuel economy?


No probably someone else on the radio. The MAF could give you a fuel economy problem but there are other factors less your driving habits, etc. Depending on the mileage of your GP, O2 sensors (front & rear) or even a clogged CAT convertor could affect fuel economy. The Bosch plugs do eave a lot to be desired.

If your MAF is causing problems, the ECU/ECM uses pre-programmed RPM values within the computer instead of the MAF signal from the flow wires. Many times a defective MAF will not give a SES check engine light either. Either way you might to have the car scanned to see if there are generic or manufacturer specific DTC error codes. There are certain codes such that are stored but do not give a SES light depending on the severity.

If the MAF doesn't correct the problem, at least you can rule it out and continue troubleshooting. Good luck!

es3153
04-02-2005, 08:03 PM
No probably someone else on the radio. The MAF could give you a fuel economy problem but there are other factors less your driving habits, etc. Depending on the mileage of your GP, O2 sensors (front & rear) or even a clogged CAT convertor could affect fuel economy. The Bosch plugs do eave a lot to be desired.

If your MAF is causing problems, the ECU/ECM uses pre-programmed RPM values within the computer instead of the MAF signal from the flow wires. Many times a defective MAF will not give a SES check engine light either. Either way you might to have the car scanned to see if there are generic or manufacturer specific DTC error codes. There are certain codes such that are stored but do not give a SES light depending on the severity.

If the MAF doesn't correct the problem, at least you can rule it out and continue troubleshooting. Good luck!

So I changed out the MAF last weekend as well as the fuel filter, since it had been a while for that filter. I replaced the air filter while I was at it. I took it to an Autozone where they put a handheld ODB-II Code reader on it. It showed a P1870 code, which the guy at Autozone pulled up on his system as a 4x4 transmission problem (???). He said the P codes were manufacture specific. Anyhow, any clue to the P1870?

And after a week of driving the car, I am still having the chugging. What would be the next thing to look at, aside from some TNT?

BNaylor
04-02-2005, 09:59 PM
So I changed out the MAF last weekend as well as the fuel filter, since it had been a while for that filter. I replaced the air filter while I was at it. I took it to an Autozone where they put a handheld ODB-II Code reader on it. It showed a P1870 code, which the guy at Autozone pulled up on his system as a 4x4 transmission problem (???). He said the P codes were manufacture specific. Anyhow, any clue to the P1870?

And after a week of driving the car, I am still having the chugging. What would be the next thing to look at, aside from some TNT?

P1870 is a GM manufacturer specific DTC code indicating "Transmission Slipping Internally".

es3153
04-04-2005, 10:18 AM
P1870 is a GM manufacturer specific DTC code indicating "Transmission Slipping Internally".

What is causing that? Will a rebuild fix it? Or does this mean a new tranny? I've been having the transmission filter / fluid changed on a regular basis.

Also, does the code need to be clearer out?

BNaylor
04-04-2005, 05:54 PM
What is causing that? Will a rebuild fix it? Or does this mean a new tranny? I've been having the transmission filter / fluid changed on a regular basis.

Also, does the code need to be clearer out?

I recommend taking the car to a reputable transmission shop and have them run it through some tests. It could be a lot of things internally. P1870 is a common DTC code on a 4T60E or 4T65E tranny and nicknamed by tranny professionals as the "Elusive 1870 Code".

It could be the TCC/PWM soleniod, TCC apply valve, convertor regulator pressure, the separator plate circuits, sprocket ratios, the turbine sensors, PCM ground, torque convertor, valve body, TCC circuit leak due to worn parts (turbine shaft) , etc. Any one or a combination could or will trigger P1870.

For now, you should reset the ECU and clear the DTC codes. Run it again and see if the code re-appears. If P1870 returns, the course of action is obvious. Good luck!

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