mechtech8100 Posted May 16, 2005 Report Share Posted May 16, 2005 Ok... this is not my car. I am a technician at a local shop and have run into a problem with a 1990 Pontiac Grand Prix STE turbo. This problem has baffled me at this point and I am hoping I might be able to find some further help from this site. The problem: The car came in for plugs and wires changed and now it has a really bad stumble or misfire. As to attempt to solve this problem the cars codes were all cleared before I got to see them. The car still would not run right and at that point I hooked the diagnostic computer and drove it up the road. When I took off I looked at the wastegate reading and as soon as it revved up the wastegate went 100%. That is where I started to get more confused as the owner came there and I talked to this individual and I was told that unknowingly to this person this car has always had this condition. I have fixed a few vacuum leaks so far but I am running out of ideas as there are no codes currently but there is a cracked cross pipe at the turbo flange that we are fixing. Could that cause this? Well any help would be great and after I fix the cross pipe I will let you know if that fixed the problem some or not. But any other ideas would be great. Thanks Quote Link to comment Share on other sites More sharing options...
god910 Posted May 16, 2005 Report Share Posted May 16, 2005 well, being very tired and just off the top of my head, you *may* have a MAP problem. That will cause your stumble, and as I'm sure you know, the 100% W/G sol. means the comp. feel's that it needs to pull boost. I thought of a sol. line problem (atmosphere to sol.) but that shouldn't cause a stumble. Of course if the MAP shows 15 psi, and tries to add fuel accordingly, and you are only getting 3-4 psi, at low angle, you could get a nasty stumble/misfire. HTH. FWIW, this is the best group of people you could have come to for your problem, hope we can help. Quote Link to comment Share on other sites More sharing options...
Intlcutlass Posted May 16, 2005 Report Share Posted May 16, 2005 Came in for plugs.... I would say with no flame intended here (because I have done this) , check to make sure the wires are in the correct order.... Quote Link to comment Share on other sites More sharing options...
mechtech8100 Posted May 16, 2005 Author Report Share Posted May 16, 2005 Yeah I know what you mean only problem is I didn''t change the plugs or wires and I am the one stuck fixing the mess up... welded the cross pipe today and have been removing twisted off bolts all day... I hate mondays. Yeah I figured I should check with those who know the car better. This thing seems like it should be a sweet car. We will see when I get it running right. Thanks Quote Link to comment Share on other sites More sharing options...
no1kicker Posted May 17, 2005 Report Share Posted May 17, 2005 Don't rule out the coils too. Does it stall? Do you smell gas? Those are signs of a bad crossover I believe, as well as rust colored engine parts above it. Quote Link to comment Share on other sites More sharing options...
GutlessSupreme Posted May 17, 2005 Report Share Posted May 17, 2005 Don't rule out the coils too. Does it stall? Do you smell gas? Those are signs of a bad crossover I believe, as well as rust colored engine parts above it. He already said the crossover was cracked, and that he just welded it but that shouldn't cause the misfire, in any case. Not directly anyway. Maybe the O2 is shot? Make sure to check wire positions first: http://img.photobucket.com/albums/v291/5speedz34/img016.jpg then, break out the spark checker. Quote Link to comment Share on other sites More sharing options...
TGPilot Posted May 17, 2005 Report Share Posted May 17, 2005 If the cross-over was cracked long enough then the 02 sensor is most likely shot. Do you get a misfire at WOT? The other thing to check is the plugs themselves. Make sure they are the proper temp range and gapped as directed... 8) Quote Link to comment Share on other sites More sharing options...
mechtech8100 Posted June 2, 2005 Author Report Share Posted June 2, 2005 ok an update on this... as of right now I have changed the coils and it runs good over 2500 RPM, still no boost tho. I am going to try the map sensor and see if that helps but it still has a misfire at lower RPM. The baffle is cracked in the front of the cross but she can't afford to change it right now... do you think the ignition module could be bad because the car runs awesome above 2500 and thats when the module doesn't do too much from what I read... any ideas? Quote Link to comment Share on other sites More sharing options...
Guest TurboSedan Posted June 2, 2005 Report Share Posted June 2, 2005 i am going to guess either the MAP sensor or bad O2 sensor. are you getting any boost at all? even 3-4psi? do you get any boost if you bypass the wastegate solenoid and run a vacuum line between the wastegate can and manifold vacuum source? btw, i know exactly which car you are talking about, i use to see that white Turbo STE just about every day when i lived down in Laramie (does the car have two big stickers on the rear trunklid? ). i raced it once in my Cutlass before i swapped the Turbo 3.1 in it and beat it, i kinda figured something must be wrong with it. anyways, good luck! Quote Link to comment Share on other sites More sharing options...
idbeast Posted June 3, 2005 Report Share Posted June 3, 2005 The cracked crossover CAN cause the stumble, also I'd replace the O2 sensor as it was stated above it WILL foul out in short order. Also check to see that it has the PROPER plugs, as I've had GM parts people try to sell me NA 3.1 parts even though I have told them it is A "V" engine (they can't seem to read their microfiche... Also do not run the new platinum rapid fire #8's as they will disintegrate... I'll try to find the proper A/C part Number... Quote Link to comment Share on other sites More sharing options...
Guest TurboSedan Posted June 3, 2005 Report Share Posted June 3, 2005 i believe it's ACDelco R42LTS. when i bought my Turbo STE engine it had three NA 3.1 plugs and three Turbo 3.1 plugs stupid people.... Quote Link to comment Share on other sites More sharing options...
idbeast Posted June 3, 2005 Report Share Posted June 3, 2005 Thanks Joshua old age is catching up to me, I couldn't remember so I had to look it up A/C part numbers Spark Plugs - R42LTS Spark Plug Wires - 12073938 Quote Link to comment Share on other sites More sharing options...
RareGMFan Posted June 3, 2005 Report Share Posted June 3, 2005 Couldn't he just unplug the vacum line going from the wastegate selenoid to the turbo to narrow down the wastegate question? I know when mine popped off on its own, it took off like a bat out of hell! :shock: Didn't know what the hell happened over night to make the turbo/boost suddenly respond 10 x better, but upon popping the hood and inspecting, I found that that line had come off. I....haven't put it back since... :oops: Quote Link to comment Share on other sites More sharing options...
Guest TurboSedan Posted June 3, 2005 Report Share Posted June 3, 2005 that's pretty risky! :shock: i think that would probably give maximum boost, since nothing would be trying to open up the wastegate. running a vacuum line from the wastegate can to a manifold vacuum source should give minimum boost (~4psi). Quote Link to comment Share on other sites More sharing options...
RareGMFan Posted June 3, 2005 Report Share Posted June 3, 2005 That's true, but he doesn't have to punch it, per se. If it responds well with the line off, he'll know it right away even with a light touch of the pedal. Then he can immediately re-attach the line knowing that the issue is related to the wastegate (either the selonoid, or the wastegate istelf, etc). If it still has stumbling issues, the problem is elsewhere. Quote Link to comment Share on other sites More sharing options...
Guest TurboSedan Posted June 3, 2005 Report Share Posted June 3, 2005 yeah, that would definately rule out a problem with the wastegate solenoid. Quote Link to comment Share on other sites More sharing options...
idbeast Posted June 4, 2005 Report Share Posted June 4, 2005 He could also have a injector issue, that being why it wants to run after 2500RPM's Quote Link to comment Share on other sites More sharing options...
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