90 Corvette Hesitation and Missing
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Joined: Apr 2007
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From: Montgomery Alabama
90 Corvette Hesitation and Missing
This is my first post on this forum so bare with me lol. I have a base 90 corvette 6 speed. Whenever I crank the car up and i run it while its cold it runs great. After about 5-10 minutes of driving it starts to stumble and hesitate at low rpms. At WOT the car will clear up but at idle or if you have it in a gear and give it some gas it will stumble and hesitate. It has new plugs, wires, filters, etc. Also whenever you run all electronics, especially A/C, it gets a lot worse. You have to take off at around 2500 RPMs just so it doesnt stumble and stall. I'd appreciate any suggestions.
Instructor
Joined: Jan 2009
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From: Tucson AZ
Well I am kind of new here to but this is what advise you are going get.
1) Have you read the codes. There are several threads covering this issue. The codes may indicate the problems. One can borrow a code reader from Autozone, etc.
2) Could be the mass air flow sensor. Tap it and see if the engine misses or runs funny. Then try just diconnecting it.
I am not sure if a 1990 has an OptiSpark those can cause problems.
1) Have you read the codes. There are several threads covering this issue. The codes may indicate the problems. One can borrow a code reader from Autozone, etc.
2) Could be the mass air flow sensor. Tap it and see if the engine misses or runs funny. Then try just diconnecting it.
I am not sure if a 1990 has an OptiSpark those can cause problems.
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Joined: Feb 2009
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From: Acworth Georgia
Is it tripping any codes? You might check just to see if a code or two have been stored.
I would start by cleaning the throttle body and pay close attention to cleaning the IAC. (Idle Air Control servo) It's mounted on the side of the throttle body. Just be careful with the pintle. The IAC controls A/F ratio at idle.
Once you come off idle, the IAC is not doing anything.
I would start by cleaning the throttle body and pay close attention to cleaning the IAC. (Idle Air Control servo) It's mounted on the side of the throttle body. Just be careful with the pintle. The IAC controls A/F ratio at idle.
Once you come off idle, the IAC is not doing anything.
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Joined: Apr 2007
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From: Montgomery Alabama
Well I am kind of new here to but this is what advise you are going get.
1) Have you read the codes. There are several threads covering this issue. The codes may indicate the problems. One can borrow a code reader from Autozone, etc.
2) Could be the mass air flow sensor. Tap it and see if the engine misses or runs funny. Then try just diconnecting it.
I am not sure if a 1990 has an OptiSpark those can cause problems.
1) Have you read the codes. There are several threads covering this issue. The codes may indicate the problems. One can borrow a code reader from Autozone, etc.
2) Could be the mass air flow sensor. Tap it and see if the engine misses or runs funny. Then try just diconnecting it.
I am not sure if a 1990 has an OptiSpark those can cause problems.
2) I don't think there is a MAF sensor on the 90s. Maybe I'm wrong ??
Thanks for the response
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Joined: Apr 2007
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From: Montgomery Alabama
Is it tripping any codes? You might check just to see if a code or two have been stored.
I would start by cleaning the throttle body and pay close attention to cleaning the IAC. (Idle Air Control servo) It's mounted on the side of the throttle body. Just be careful with the pintle. The IAC controls A/F ratio at idle.
Once you come off idle, the IAC is not doing anything.
I would start by cleaning the throttle body and pay close attention to cleaning the IAC. (Idle Air Control servo) It's mounted on the side of the throttle body. Just be careful with the pintle. The IAC controls A/F ratio at idle.
Once you come off idle, the IAC is not doing anything.
Yeah I thought about trying the IAC but that really wouldn't explain the hesitation at normal speeds.
The A/C and electronic thing is what trips me out.
EDIT: Oh yeah, and it seems to be running rich. I don't know if it's normal for these cars, but the exhaust smells like gas most of the time. I didn't think it was supposed to be that much of a gas smell. Thanks
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Joined: Mar 2008
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From: Cumming Ga
This is my first post on this forum so bare with me lol. I have a base 90 corvette 6 speed. Whenever I crank the car up and i run it while its cold it runs great. After about 5-10 minutes of driving it starts to stumble and hesitate at low rpms. At WOT the car will clear up but at idle or if you have it in a gear and give it some gas it will stumble and hesitate. It has new plugs, wires, filters, etc. Also whenever you run all electronics, especially A/C, it gets a lot worse. You have to take off at around 2500 RPMs just so it doesnt stumble and stall. I'd appreciate any suggestions.
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Instructor
Joined: Jan 2009
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From: Tucson AZ
Good point. I was thinking of my 94. Sorry for the bad advice.
Burning Brakes
Joined: Oct 2004
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From: Pearland Texas
Probably your injectors, if they are stock Multecs they could be failing. Hopefully you haven't ran Seafoam or another brand of injector cleaner thru them, that could have killed them. Try putting an Ohm meter on each injector top and check the impedence. They should be around 16-18 ohms, mostly they should be fairy close. Check those and report back.
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Joined: Apr 2007
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From: Montgomery Alabama
Thanks
Thread Starter
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Joined: Apr 2007
Posts: 82
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From: Montgomery Alabama
Probably your injectors, if they are stock Multecs they could be failing. Hopefully you haven't ran Seafoam or another brand of injector cleaner thru them, that could have killed them. Try putting an Ohm meter on each injector top and check the impedence. They should be around 16-18 ohms, mostly they should be fairy close. Check those and report back.
Burning Brakes
Joined: Oct 2004
Posts: 898
Likes: 1
From: Pearland Texas
Burning Brakes
Joined: Oct 2004
Posts: 898
Likes: 1
From: Pearland Texas
The top of the injector has a metal clip on it. Just push it in with a screwdriver and pull the plug off at the same time. If you pry on the side it could go "BOING" and fly off somewhere.
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Joined: Apr 2007
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From: Montgomery Alabama
Haha I appreciate the advice. If one or two are bad do I just replace those or do I have to replace all 8 of them?
1st Gear
Joined: Jan 2006
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You need to check the fuel pressure. If you have the FSM it tells you how to do a leak down test on the injectors.You also should check the ohms on the injectors with a digital ohm meter. They should be at
16 ohms. GM says less than 10 replace, from what I have learned under 12 they are headed south and time to replace.
Yours sounds a little like mine before I replaced the injectors with the Bosh III from FIC
Scav.
16 ohms. GM says less than 10 replace, from what I have learned under 12 they are headed south and time to replace.
Yours sounds a little like mine before I replaced the injectors with the Bosh III from FIC
Scav.
Thread Starter
Advanced
Joined: Apr 2007
Posts: 82
Likes: 0
From: Montgomery Alabama
You need to check the fuel pressure. If you have the FSM it tells you how to do a leak down test on the injectors.You also should check the ohms on the injectors with a digital ohm meter. They should be at
16 ohms. GM says less than 10 replace, from what I have learned under 12 they are headed south and time to replace.
Yours sounds a little like mine before I replaced the injectors with the Bosh III from FIC
Scav.
16 ohms. GM says less than 10 replace, from what I have learned under 12 they are headed south and time to replace.
Yours sounds a little like mine before I replaced the injectors with the Bosh III from FIC
Scav.
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Joined: Apr 2007
Posts: 82
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From: Montgomery Alabama