Low idle on 1982
Thread Starter
Intermediate
Joined: Dec 2006
Posts: 48
Likes: 0
From: Prairieville LA
Low idle on 1982
Recently my car has started idling lower than it used to. It idles most of the time at 500-600 rpm, which makes the car run really rough, with a whole lot of shaking going on. I say idles "most of the time" because, on occasion it idles 700-800 rpm and the idle is smooth as silk. Each time I pull up to a stop sign the idle speed could be different. I would say 4 times out of 5 it is low. Idle is consistent whether in park, neutral, or drive, with A/C on or off.
As far as I know the idle speed is controlled by the ECM so I'm not sure if there is a way to increase the idle speed.
Checked ignition timing and reset to 6 degrees BTC ( was 8), but no change regarding idle. Car runs smooth off idle.
Could a vacuum leak cause this? Don't see any obvious leaks but I couldn't rule out the possibility.
Any ideas would be appreciated.
As far as I know the idle speed is controlled by the ECM so I'm not sure if there is a way to increase the idle speed.
Checked ignition timing and reset to 6 degrees BTC ( was 8), but no change regarding idle. Car runs smooth off idle.
Could a vacuum leak cause this? Don't see any obvious leaks but I couldn't rule out the possibility.
Any ideas would be appreciated.
Instructor
Joined: Aug 2006
Posts: 104
Likes: 0
From: Apache Junction Arizona
Yes, a vacuum leak will cause this. CFI's react badly to any vacuum leaks. Also check your throttle shafts on your TB's - if you can wiggle the shafts side to side where there is play; you have a good vacuum leak there and will need to have the throttle body shafts bushed.
Check out these sites for a ton of info on your CFI 82.
Good Luck!
http://www.crossfire.homeip.net
http://crossfireinjection.net/
Check out these sites for a ton of info on your CFI 82.
Good Luck!
http://www.crossfire.homeip.net
http://crossfireinjection.net/
Le Mans Master
Joined: Apr 2001
Posts: 5,000
Likes: 1
From: Minneapolis, Mn USA
Usually a vacuum leak causes a higher idle like 800-1200rpm in gear with a summertime ambient engine.
Low idle could suspect many possible causes, so I would go over the basics:
1) MAP sensor is bad or leaking. Check this by disconnecting it. If your idle increases the MAP is working. If no change, you should replace it.
2) Throttle positions sensor. check-set for 5.25 at zero throttle
3) fuel pressure -less likely if running better at higher RPM, but who knows on this one. 9-13PSI with higher the better
4) Base Timing Also how does your crank dampener look. It could be the rubber is letting go and your timing mark is no longer accurate.
5) TBI fuel leaks or bad injector patterns
6) The TBs out of sync. A rebalance would be required with a manometer.
Lastly was BUBBA there? Does your system look unmolested?
Links:
CFI Tune Up
http://www.corvettefever.com/techart...ing/index.html
CFI Hop up
http://www.corvettefever.com/howto/51218/index.html
Low idle could suspect many possible causes, so I would go over the basics:
1) MAP sensor is bad or leaking. Check this by disconnecting it. If your idle increases the MAP is working. If no change, you should replace it.
2) Throttle positions sensor. check-set for 5.25 at zero throttle
3) fuel pressure -less likely if running better at higher RPM, but who knows on this one. 9-13PSI with higher the better
4) Base Timing Also how does your crank dampener look. It could be the rubber is letting go and your timing mark is no longer accurate.
5) TBI fuel leaks or bad injector patterns
6) The TBs out of sync. A rebalance would be required with a manometer.
Lastly was BUBBA there? Does your system look unmolested?
Links:
CFI Tune Up
http://www.corvettefever.com/techart...ing/index.html
CFI Hop up
http://www.corvettefever.com/howto/51218/index.html
