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Discussion Starter #1
I have an 86 non turbo, automatic. Just looking for some ideas as to what may be causing the car to idle rough. It only happens SOMETIMES....When sitting at a stop light, for example, and holding the brake, the car will start to sputter a bit and shake for a few seconds while the RPM's drop to about 750 - 800, otherwise it idles around 1000-1100 I thnk. The car doesn't stall, but it sure feels like it is going to. Then at the next stop light nothing happens and all is well. Very strange, but thanks for any help.

D



Post Edited (Aug 28, 7:30am)
 

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750 800 is normal idle. Your Z is idling to high anyway. As far as it feeling like its going to stall at 750 800RPM? I dont think so. My Z 86T has a problem right now and will idle rough at 400 for a min or two before stalling out.
 

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Yeah, the idle is a bit higher than spec. Have it adjusted (or otherwise find the cause of the high idle) and that should reduce the heat in the tranny in stop-start traffic. Check the TPS adjustment as well.
Intermittent problems are certainly frustrating.
The next time it idles rough at a stop, pull on the handbrake and release the footbrake while remainig in D. If the idle smooths out then you can reasonably assume there is some problem with the vacuum system in brake booster. Problems in the booster are not common but also not impossible.

Intermittent varying idle may suggest problems with the fuel pump voltage control, or the fuel pump's response to lowered voltage. That can require running a fuel pressure gauge into the cabin to aid diagnosis.
 

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Thank you for the input.......actually now that you mention it, I did notice that the Volt guage was registering closer to 12 rather than 15 volts.....does that seem to indicate anything specific to you???

d
 

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If the volts are 12V at 750-800rpm then that is not too bad. At 1000-1100rpm I would expect the volts to be higher.
 
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