Help! Engine problems with an `85
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Joined: Aug 2005
Posts: 73
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From: Germany
Help! Engine problems with an `85
Im new to this forum, and desperately need some help with our `85 4-speed Vette. The engine has been upgraded with higher-flow intake runners and a 52mm throttle body. Here`s the story:
The Autoxray scan tool we bought told us that the MAT had failed, which prompted us to not only replace it but to relocate it to the air filter housing or whatever its called with a relocation kit to give better readings and to ease removal of the sensor (it was a pain to have to remove the intake plenum to access it). Thats when all the problems got started, reasons unknown. When left to idle, the engine would idle for about 5-10 seconds before stalling. It seemed that the motor was fighting against death, it was shaking so violently. Any attempts to rev it up would result in an nearly immediate stall after depressing the gas pedal. Interestingly, however, with the scan tool hooked up, the engine would idle and run just fine. The tool told us now that the Coolant Temp Sensor was bad, so we replaced that too. It made no difference. Then the MAF had to go in place of a new one. Still no inprovements. Finally, the IAC turned out to be bad as well. A new one took its place. The characteristics of the engine changed a bit, still stalling when left to idle, but it could be revved up and kept from dying by letting the engine run at around 22-2400 rpms. And thats where we are right now. Id really appreciate any feedback that can help get her back on the road.
The Autoxray scan tool we bought told us that the MAT had failed, which prompted us to not only replace it but to relocate it to the air filter housing or whatever its called with a relocation kit to give better readings and to ease removal of the sensor (it was a pain to have to remove the intake plenum to access it). Thats when all the problems got started, reasons unknown. When left to idle, the engine would idle for about 5-10 seconds before stalling. It seemed that the motor was fighting against death, it was shaking so violently. Any attempts to rev it up would result in an nearly immediate stall after depressing the gas pedal. Interestingly, however, with the scan tool hooked up, the engine would idle and run just fine. The tool told us now that the Coolant Temp Sensor was bad, so we replaced that too. It made no difference. Then the MAF had to go in place of a new one. Still no inprovements. Finally, the IAC turned out to be bad as well. A new one took its place. The characteristics of the engine changed a bit, still stalling when left to idle, but it could be revved up and kept from dying by letting the engine run at around 22-2400 rpms. And thats where we are right now. Id really appreciate any feedback that can help get her back on the road.
Le Mans Master
Joined: Jul 2001
Posts: 6,252
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From: Silicon Valley Kalifornia
Ok - I'll give it a whirl - You should do a "minimum idle air setting". A factory or Hanes manual will show you the procedure. You've changed the characteristics of idle by introducing a different throttle body. Computer needs to know this new setting 
Last edited by GRX; Aug 31, 2005 at 02:51 PM.
Drifting
Joined: Mar 2005
Posts: 1,923
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From: GA
Originally Posted by racer85
When left to idle, the engine would idle for about 5-10 seconds before stalling. It seemed that the motor was fighting against death, it was shaking so violently. Any attempts to rev it up would result in an nearly immediate stall after depressing the gas pedal. .
