Lumina 3.4L DOHC v6 1994 (OBD I)

It has had new plugs, wires, oil change, timing belt, fan belt, removed AC, etc. in last 8 months.

I was going to do soon: transmission fluid change/filter, maybe oxygen sensor, and check/replace EGR, PVC, and maybe some cracking rubber hose.

Anyone have an idea why the computer seems to think it needs to re-learn idle rates, or why the thing is running rough in morning now that its cold outside overnight?

What is the most likely cause of this behaviour?

Beyond plugs and wires I have no idea how to perform a tune-up. I did the gas filter as well, only a few months ago. I added some injector-cleaner a few gastanks back, and put in a couple of quarts of synthetic oil. All these helped in their way at the time.

But this seems closely related to cold weather (below freezing at night).

You mean that chick can't keep it warm?
No seriously it sounds like a temp sensor, check your wiring from temp unit. Just check electrical connections. I'm not sure where 3.4L stuff is. I have a 3.1L.

This could be anything from a bad coolant temp sensor, bad IAC valve, Stuck EGR, vacuum leak, etc...

Is the check engine light on, and if so have you pulled the codes?

This could be anything from a bad coolant temp sensor, bad IAC valve, Stuck EGR, vacuum leak, etc...

Is the check engine light on, and if so have you pulled the codes?

Engine light has been on for 5 years.

Unable to pull codes:

This /94 3.4L v6 Eurosport is the one vehicle/year (transition OBD I) that is not supported by either the GM OBD reader or 3rd party OBD II readers.

I think there is a $300 super-code reader but its out of my price range.

There is no "Autozone" here in Canada. CanTire does not read codes free. I don't even think anyone around here can, except for a GM dealership, if at all.

I gave up on that after many tries. Shorting out the leads does not make it display the codes in "Morse" either, at least on this car.

The ECM is a substitute from a /95 Monte Carlo, acquired at the wrecker's.

The car was running great all summer and fall.

It did a few re-calibrations by itself when I did the timing belt, unhooked the battery, etc.

Can anyone tell me how and where the EGR is and how to test/change it? That sounds like something that should be easy.

Also the coolant may be an issue:

The water pump was changed a year or 2 ago. If the 'wrong' coolant was put in (i.e. not "Dex") there may be sludge blocking or slowing the cooling system.

I read about this happening to someone else who was flushing their system.
Apparently mixing DEX with other coolants could cause the formation of a 'gel' or sludge.

It seemed quite an elaborate and time-consuming job to completely flush out the "DEX" and replace with a more reliable coolant.

I mention this because for a while now it has seemed to run hot (could the cooling system be semi-plugged?).

The stuff in there now is a greenish color, but I thought that DEX was pink. Possibly someone changed over but did not properly flush system....

Any comments on this possibility?

You mean that chick can't keep it warm?
No seriously it sounds like a temp sensor, check your wiring from temp unit. Just check electrical connections. I'm not sure where 3.4L stuff is. I have a 3.1L.


Would the temp sensor be in the cooling system?

Check fuel pressure. See youtube video 'fuel pressure' (easy test).

Loping idle is vacuum leak. 30 year old lawnmower, or a new car on the lot. If it sucks air where it ain't supposed to, it lopes.

Brick on pedal, block TB arm, anything to get a STEADY idle. 1200rpms or so... Feed starting fluid spray, A LITTLE AT A TIME, EVERYWHERE. Rev increase is the leak.

In a tough spot to pinpoint? Light a book of matches, blow it out while the heads are burnin', and feed the smoke to the leak.

Quick Update:

I'm reposting my latest discovery here, for people who may be searching:


Meanwhile, I was thinking about the fact that the O2 sensor has a heater built into it, which is on when the key is on.

They used to say DON'T leave your key on, because you'll burn out the points on your distributer. That was in the days of carburetors.

Since this is fuel injection, (it has no mechanical 'points') I figured that it should do no real harm to leave the key on (other than drain battery).

So I have started turning the key on in the morning for about 40 seconds before starting the car. (the O2 sensor has to be at about 600 degrees before it works properly).

Incredibly, now the car seems to start properly in the morning as though it was already warmed up! (I haven't tested this in 20 below zero weather yet).

The O2 sensor may have some life in it after all. Perhaps not letting the car go into "open loop" mode on cold mornings will prevent plugs and cat converter from fouling.

Now all I need probably do is find a way to clear out whatever soot and crap has built up in both the O2 sensor and Cat Converter.

Isn't there some product(s) that will clear out soot and/or burn off deposits? Maybe I don't have to change the 02 sensor yet at all.

Maybe I can just clean it "in situ" somehow without dismantling the car.

I hope someone knows if or how I can clean out the exhaust system from previous foulings and rich idling. Any ideas?

To get the codes read, you could take it to a repair facilty, which may charge you $40-$60, but that would be better than changing a $200 EGR valve you don't need.

Did you swap out the PROM chips from your old ECM to the new one, or did you install it as-is from the donor vehicle? If you didn't swap the PROM, that is probably most of your issue as each PROM is calibrated to that specific vehicle.

Finally, the 3.4 DOHC's are known for intake leaks that only affect operation when cold. As the weather gets colder, the metal shrinks more, causing gaps that the intake gakets can't keep sealed. As the engine warms up, everything expands and the engine will run better.

To get the codes read, you could take it to a repair facilty, which may charge you $40-$60, but that would be better than changing a $200 EGR valve you don't need.

.

Anyone have an idea why the computer seems to think it needs to re-learn idle rates

http://www.stripers247.com/phpBB2/images/smilies/thinking.gif

Let's ask the computer.

Engine light has been on for 5 years.
http://www.digitalcorvettes.com/forums/images/smilies/smilie_thud.gif
http://www.digitalcorvettes.com/forums/images/smilies/smilie_thud.gif
http://www.digitalcorvettes.com/forums/images/smilies/smilie_thud.gif
If the computer is talkin', ya' gotta' listen. Maybe that's a starting point???

Save the $40 - $60.

Use a $.07 paper clip.

http://www.corvettebuyers.com/c4vettes/94_96_code_display.JPG

Get your codes, and post them back. NOTHING ELSE TO DO BUT THAT.

more Updates:

(1) EGR Valve: I was only thinking of changing the EGR because I did not know it might cost $200-$300. I assumed it was either a $10 part or something I could get from a wrecker (and I probably will if I need to). The second reason I had for changing the EGR was because I have already swapped out and/or replaced nearly everything else. I have been mistakenly saying in a few previous posts that I changed the EGR valve, when in fact I actually changed the PCV Valve (a $7 part).

(2) "Repair Facility": In the Canadian countryside, there's no such animal as a(n honest) 'repair facility'. We try to glue shit together with duct-tape around here. And there's no money for luxuries like "labour". its a DIY situation.

(3) /95 Monte Carlo ECM:
Did you swap out the PROM chips from your old ECM to the new one, or did you install it as-is from the donor vehicle? If you didn't swap the PROM, that is probably most of your issue as each PROM is calibrated to that specific vehicle.
Its a fair question. But the answer is sad and simple. The ECM that's in this car was there when I bought it second hand, and I have no idea of the history of the vehicle. But its almost a certainty that nobody did any PROM swapping. People here grab something from the wrecker and shove it in. If the car starts, thats considered a successful repair. The only reason I know this much is because a wrecker scribbled "/95 Monte Carlo" in crayon on the case for the ECM. Any original equipment PROMs must be considered long gone at this point.

(4) Fuel Pump/Pressure:
Check fuel pressure. See youtube video 'fuel pressure' (easy test).

No need, nor any sense to it. Fuel pump works fine. Car cruises on highway without any problems when warm. Lots a power, nice engine. Problem is as previously stated. The thing doesn't know how to cold-start without wasting gas, idling all over the map, conking out and fouling its own plugs. It needs an adult diaper before it waking it up.

(5) Intake Leaks:
Finally, the 3.4 DOHC's are known for intake leaks that only affect operation when cold. As the weather gets colder, the metal shrinks more, causing gaps that the intake gakets can't keep sealed. As the engine warms up, everything expands and the engine will run better.

This sounds like useful information. I presume that the only fix is to re-gasket the intake manifold. Fair enough. If I can't get anywhere with other things, I will get to this too.

(6) Computer Codes:

If the computer is talkin', ya' gotta' listen. Maybe that's a starting point???

Save the $40 - $60.

Use a $.07 paper clip.

http://www.corvettebuyers.com/c4vettes/94_96_code_display.JPG

Get your codes, and post them back. NOTHING ELSE TO DO BUT THAT.

I'm apparently not the only one not listening. Of course I'll save the $40-60, since I haven't got it to spend. And the paper-clip trick doesn't work on this vehicle, as I have previously explained!

It may be that the pin-out is the problem, or it may be that the ECM/software for a 3.4L v6 HAS NO Facility to dump codes with a paper-clip, or it may be that the substitute /95 Monte Carlo ECM is the reason for no codes. Or it may be that the 'code' is simply that the ECM has some stupid software bug in it which is unique. I may get around to experimenting with substitute ECMs and PROMs, but not till I have inherited lots of time and money.

The main point is that no codes are forthcoming from this LEMON, and finally, your pinout diagram seems hopelessly wrong, since on the readout plug I have already replaced once, there is NO WIRE connected to pin 12. I have posted the actual pinout of the plug elsewhere, but essentially it has the two end-pins on the right as the 'live pins'. The one in the middle of the plug is apparently for a low-speed transmission readout (perhaps to a proprietary Dealer-readout device?).

I have shorted all possible pins and got no codes. So actually, there is NOTHING ELSE TO DO BUT do something ELSE.

(5) Intake Leaks:


This sounds like useful information. I presume that the only fix is to re-gasket the intake manifold. Fair enough. If I can't get anywhere with other things, I will get to this too.
.

Well, no, at least not till after you test. See post #6.

The main point is that no codes are forthcoming

Engine light has been on for 5 years.

If you have a check engine light, you have code(s). And if the light goes out when you turn off at night, then it will blink your codes under the right circumstances. One of those circumstances is with a paper clip.

If your ALDL connector is different than the one I posted, you need to identify the pinouts for yours, and find out which 2, when jumped, will tell you your codes.

If you have a check engine light, you have code(s). And if the light goes out when you turn off at night, then it will blink your codes under the right circumstances. One of those circumstances is with a paper clip.

If your ALDL connector is different than the one I posted, you need to identify the pinouts for yours, and find out which 2, when jumped, will tell you your codes.

I know you're finding it hard to believe, but reading codes on this /94 Lumina with a /95 Monte Carlo ECM/PCM is simply bullshit.

I have done a search, to prove to myself that I am indeed not living in an alternate universe, but the same one in which you reside.

I found the following informative, but utterly useless to a Canadian post:


http://www.automotiveforums.com/vbulletin/showthread.php?p=5711717


...
The only 95's that come with OBD2 are the ones that were sold in California with the 3.8's. If it's got a 3.4, then it's definitely OBD1.

I never found any paper clip trick to work.

But what I did find to work was educating the people at Advanced Auto parts on how to use their diagnosis scanners. If you're trying to find out the codes in your system, then I would recommend this.

Go up to Advance Auto, Autozone, or whatever auto parts store you have around you.

Tell the person that you need to have you car scanned for codes. They'll ask what year is it for, you say 1995. They say "Sorry, it has to be 1996 and up for us to scan it." This is the fun part.. Explain to then that you have an OBD2 port in your car, so they can scan it. This should intrigue them enough to at least go out and give it a look over. Now when the person comes out to the car to scan it, tell him/her to manually enter the cars information (Year/Make/Model/Engine) into the scanner device, and then hook it up to the OBD port to scan it. It should scan fine, and they should take you back inside to print out the codes showing what was wrong.

The majority of the employees don't realize that their scanners do read OBD1 codes, they're just not taught how to fully use them. They don't have a cord that plugs into the OBD1 port, that's why they tell everyone with OBD1 that they can't scan it. But their scanners will read OBD1, that's why you must enter the cars information into the scanner. Otherwise, if the employee just hooks it up to the port and starts to try to scan, it will say there was an error. Once the employee enters the information about the car into the scanner, it then recognizes that it will be reading an OBD1 system instead, and should work just fine for you.

In case you're wondering, yes I've had this run in several times. :rolleyes:
__________________
- Jason



P.S.:

/94 Lumina owners should note with horror and amusement, that this pinout for the ALLEGED scancodes is ALSO nothing at all like the actual wiring they will find under their dash.

Another link in the above thread gives the actual (original) pinout for the smaller plug:


Title:Pre-1996 ENGINE Trouble Codes



Author:Tink



So your "check engine" or "service engine soon" light has come on. If you have a pre-1996**, you don't need an expensive scan-tool or code reader to check the codes, just a simple paper clip. Locate the ALDL (Assembly Line Diagnostic Lead). It is usually under the driver's side of the dash. For most 1994 and back (OBD 1, 12 pin ALDL) short terminals A & B.
http://s-series.org/albums/album81/aldl.jpg
In 1995 GM changed to OBD 1.5. Some late 1994 models are also OBD 1.5. For these (OBD 1.5, 16 pin ALDL) short terminals 5 & 6.
http://www2.eboard.com/boards/9/50/68/tink/att-984326/aldl.jpg
Turn key on, but do not start engine. Find and Short terminals with a paper clip. The check engine light will begin to flash. The ECM (computer) will display a "code 12" by flashing the "service engine soon" light, indicating that the system is operating. A code 12 is simply one flash, followed by a brief pause, then two flashes in quick succession. This code will be flashed 3 times. If no other codes are stored, code 12 will flash until the diagnostic terminal ground is removed. After flashing code 12 3 times, the ECM will display any stored trouble codes. Each code will be flashed 3 times, then code 12 will be flashed again, indicating that the display of any stored trouble codes has been completed.



However, In my car, the pinout is actually different again, with wires going to pin 6 and 12, (not 5).

But all this is moot in any case, since I have already explained in several previous posts that I have shorted out every possible combination of live pins in the plug with NO CODES flashed as a result. This finding is identical to that of the poster quoted above.

Paper Clips don't work on this LEMON.

new egr = $225. but before you do that, clean it. rip it out, literally fill it with deep-creep, spray a ton down the hose too. put it back in, it will smoke for a good 10 minutes out the exhaust. simply remove the wiring off the top of it, it pops out. pull the two bolts holding it in, its that easy. you SHOULD buy new gaskets for it before putting it back in. they're $2.20 each.

computer = $225 installed including labor. i find it funny that people actually pay $700 for this.

performance chip = $99 this alone when options are chosen right will make the biggest difference as far as idle/temp goes. i elected to run 180 temp "matched with thermostat" and egr OFF.

220,00 miles later, still runs like new...

forgot to mention, it NEVER runs over 180 degrees. even at long red lights...

new egr = $225. but before you do that, clean it. rip it out, literally fill it with deep-creep, spray a ton down the hose too. put it back in, it will smoke for a good 10 minutes out the exhaust. simply remove the wiring off the top of it, it pops out. pull the two bolts holding it in, its that easy. you SHOULD buy new gaskets for it before putting it back in. they're $2.20 each.


Thanks for this tip. I'm going to try this when I get the chance. I'll make sure I have the right gaskets first.








performance chip = $99 this alone when options are chosen right will make the biggest difference as far as idle/temp goes. i elected to run 180 temp "matched with thermostat" and egr OFF.

220,00 miles later, still runs like new...

forgot to mention, it NEVER runs over 180 degrees. even at long red lights...



I ain't got $100 (especially for a $2.00 Eprom) but hey:

If you have tried a few of these and want to sell an old one second hand, with less than optimal features for your own tastes, I woulld be interested!

I believe we have the same engine ( /94 3.4L v6 DOHC)

For others, I'm still using the "turn key on for 40 secs before starting", and the darn car starts fine now. This seems to heat up the O2 sensor enough to prevent the car from going into "open loop" mode.

I'm wondering if I need a new O2 sensor, or if I just need to clean it off somehow. Perhaps there's an additive or method of burning off junk.

As I stated in post #8, you cannot jump the ALDL on this car with a paper clip. THE ONLY WAY TO GET THE CODES IS TO TAKE IT TO A REPAIR FACILITY with a professional scan tool (GM tech-1 or Snap-on MT2500 for example). Without doing so, you could spend $1,000's guessing and swapping parts. IF you refuse to scan it, you might as well junk it!

To the OP, a 94 Grand Prix 3.4 takes a GM #16196709 PROM, a 95 Monte Carlo 3.4 takes a GM #16229657 (new number) or 16201690 (old OEM #) PROM. Check the PROM # in your car now, and if it isn't the 16196709, you might as well bite the bullet and order the correct PROM. If you don't, this car will never run right no matter how many parts you swap.

As I stated in post #8, you cannot jump the ALDL on this car with a paper clip. THE ONLY WAY TO GET THE CODES IS TO TAKE IT TO A REPAIR FACILITY with a professional scan tool (GM tech-1 or Snap-on MT2500 for example). Without doing so, you could spend $1,000's guessing and swapping parts. IF you refuse to scan it, you might as well junk it!

To the OP, a 94 Grand Prix 3.4 takes a GM #16196709 PROM, a 95 Monte Carlo 3.4 takes a GM #16229657 (new number) or 16201690 (old OEM #) PROM. Check the PROM # in your car now, and if it isn't the 16196709, you might as well bite the bullet and order the correct PROM. If you don't, this car will never run right no matter how many parts you swap.

Thanks for the info: I think I'll jot that down next time I pull the PCM or rattle it around.