1992 3.1 Finicky throttle issues
#1
10-16-2015, 06:14 PM
1992 3.1 Finicky throttle issues
Hello folks. I looked for a similar thread but couldn't find anything describing exactly what my 92 RS is doing.
I know my name says 93 but now I have a 92. Saw it at a local Chev dealer and I know the salesman well. Guess a guy traded it in on a 2013 SS. Lol bit ot of an upgrade right? For mearly 2400 and in near perfect shape, 25th anniversary, white w/ red int and red SS stripes. ... well I couldn't pass it up. Even though it is a 3.1 v6.
PROBLEM: At ideal the RPMs go up and down. Idels at 1100 or so then drops for a second or two down to 400 to 600. It almost dies sometimes but never really does. This is only in drive when Im stopped. In park or neutral its fine. It also has a bit of hesitation when you first press the gas to get going. Only for a second though. Cruising, accelerating, and low speeds are fine. When I stop is where it gets cranky. I have driven a 74 ford for most of my life and and dealt only with mechanical aspects and carburetion. Sensors and computers are not my specialty but any means. Any help or hints are very very appreciated.
Best regards,
Cody
I know my name says 93 but now I have a 92. Saw it at a local Chev dealer and I know the salesman well. Guess a guy traded it in on a 2013 SS. Lol bit ot of an upgrade right? For mearly 2400 and in near perfect shape, 25th anniversary, white w/ red int and red SS stripes. ... well I couldn't pass it up. Even though it is a 3.1 v6.
PROBLEM: At ideal the RPMs go up and down. Idels at 1100 or so then drops for a second or two down to 400 to 600. It almost dies sometimes but never really does. This is only in drive when Im stopped. In park or neutral its fine. It also has a bit of hesitation when you first press the gas to get going. Only for a second though. Cruising, accelerating, and low speeds are fine. When I stop is where it gets cranky. I have driven a 74 ford for most of my life and and dealt only with mechanical aspects and carburetion. Sensors and computers are not my specialty but any means. Any help or hints are very very appreciated.
Best regards,
Cody
#2
10-17-2015, 09:44 AM
This is a multiport fuel injection system so there are a lot of things that can cause a idle issue. Based on your complaint I would suspect a lazy IAC motor (Idle Air Control). If the motor is moving too slowly it will over correct in both direction. This can also be cause by the IAC being slowed down buy sludge in the IAC port or just a bad IAC motor. Step one would be to clean out the port. Second thing I would check would be the EGR valve leaking at the seal. A small leak will only effect idle.
The problem with figuring out idle issues is that as most problems start to effect idle first. A tiny leak in an injector or spark issue can cause this. A scan tool and the knowledge of what sensor input should look like would narrow the possibilities greatly.
Search youtube for:
Cleaning IAC
Homing GM IAC
Checking EGR Valve for leaks. ( you will need a EGR valve gasket)
All GM pre 93 EFI are similar but you want to look for videos closest to your year.
Good Luck
The problem with figuring out idle issues is that as most problems start to effect idle first. A tiny leak in an injector or spark issue can cause this. A scan tool and the knowledge of what sensor input should look like would narrow the possibilities greatly.
Search youtube for:
Cleaning IAC
Homing GM IAC
Checking EGR Valve for leaks. ( you will need a EGR valve gasket)
All GM pre 93 EFI are similar but you want to look for videos closest to your year.
Good Luck
#4
12-15-2015, 05:47 PM
Well no good news from the front. I found the code 12-32 According to the books its the EGR. I bought a new one but that didn't help sadly. Plus its a electronic one which was spendy.
I have noticed that it only does it when its warmed up. Seems like it may be getting worse. I dont know if that's true but it seems like it. Vac leak? IACV? Uhg what a pain. If anyone has any ideas thathat'd be great.
I have noticed that it only does it when its warmed up. Seems like it may be getting worse. I dont know if that's true but it seems like it. Vac leak? IACV? Uhg what a pain. If anyone has any ideas thathat'd be great.
#5
12-15-2015, 07:43 PM
Code 12 is just no input signal to the ECM (the car is not running) If I remember right code 32 can be set by several different things. You need to run through the trouble shooting steps in the manual.
By changing the EGR valve you kind of proved that it is not a EGR valve leak. Like I said above there are a lot of things that can cause this. No one is going to be able to say what this is they, like me, can only guess. This is why professional make decent money. The mechanic that would work on a "driveablity" issue like this most likely has a degree in automotive technologies 30-40K in his own tools and the shop could have another 100K in diagnosis equipment for him to use.
I tell most people the same thing when their car is not running right. Make sure everything with maintenance is up to date. Plugs, wire, fuel and air filter, Clean the IAC, clean the EGR. If it is still acting up take to a pro. In the end this is almost always cheaper then "throwing parts at it" (AKA guessing)
Normally a vacuum leak just causes high RPMs not up and down idle. The exception to that is when the vacuum leak is to a single cylinder. That can cause all kinds of havoc as ECM tries to "fix" the lean exhaust by adding fuel to all the cylinders.
By changing the EGR valve you kind of proved that it is not a EGR valve leak. Like I said above there are a lot of things that can cause this. No one is going to be able to say what this is they, like me, can only guess. This is why professional make decent money. The mechanic that would work on a "driveablity" issue like this most likely has a degree in automotive technologies 30-40K in his own tools and the shop could have another 100K in diagnosis equipment for him to use.
I tell most people the same thing when their car is not running right. Make sure everything with maintenance is up to date. Plugs, wire, fuel and air filter, Clean the IAC, clean the EGR. If it is still acting up take to a pro. In the end this is almost always cheaper then "throwing parts at it" (AKA guessing)
Normally a vacuum leak just causes high RPMs not up and down idle. The exception to that is when the vacuum leak is to a single cylinder. That can cause all kinds of havoc as ECM tries to "fix" the lean exhaust by adding fuel to all the cylinders.
#6
12-15-2015, 09:17 PM
Code 12 is just no input signal to the ECM (the car is not running) If I remember right code 32 can be set by several different things. You need to run through the trouble shooting steps in the manual.
By changing the EGR valve you kind of proved that it is not a EGR valve leak. Like I said above there are a lot of things that can cause this. No one is going to be able to say what this is they, like me, can only guess. This is why professional make decent money. The mechanic that would work on a "driveablity" issue like this most likely has a degree in automotive technologies 30-40K in his own tools and the shop could have another 100K in diagnosis equipment for him to use.
I tell most people the same thing when their car is not running right. Make sure everything with maintenance is up to date. Plugs, wire, fuel and air filter, Clean the IAC, clean the EGR. If it is still acting up take to a pro. In the end this is almost always cheaper then "throwing parts at it" (AKA guessing)
Normally a vacuum leak just causes high RPMs not up and down idle. The exception to that is when the vacuum leak is to a single cylinder. That can cause all kinds of havoc as ECM tries to "fix" the lean exhaust by adding fuel to all the cylinders.
By changing the EGR valve you kind of proved that it is not a EGR valve leak. Like I said above there are a lot of things that can cause this. No one is going to be able to say what this is they, like me, can only guess. This is why professional make decent money. The mechanic that would work on a "driveablity" issue like this most likely has a degree in automotive technologies 30-40K in his own tools and the shop could have another 100K in diagnosis equipment for him to use.
I tell most people the same thing when their car is not running right. Make sure everything with maintenance is up to date. Plugs, wire, fuel and air filter, Clean the IAC, clean the EGR. If it is still acting up take to a pro. In the end this is almost always cheaper then "throwing parts at it" (AKA guessing)
Normally a vacuum leak just causes high RPMs not up and down idle. The exception to that is when the vacuum leak is to a single cylinder. That can cause all kinds of havoc as ECM tries to "fix" the lean exhaust by adding fuel to all the cylinders.
I wasn't "Just throwing parts at it. " The old one had some voodoo the previous owner tried. It had a bunch of self made metal plates. He had tried to block it off I think. They were all rusted with holes drilled in it. After seeing that and the condition it was in, I thought it best to get a new one anyway. I was hoping that was the problem but its never that easy.
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