Idle Fluctuation problem
09-05-2004 | 01:22 AM
#1
Thread Starter
Junior Member
Joined: Aug 2004
Posts: 78
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From: Orange County, CA
Car: 89 Trans AM GTA
Engine: 5.7L
Idle Fluctuation problem
Hello:
My car has been running awesome until today. Today on my way home I got gas and drove home, being a hot day when I pulled into my driveway I noticed the car was running a little above the 220 so I put some more water in the reservoir. Later on when I started the car the idle would fluctuate down to about 500 and the headlights would dim and the back up to 650 and keep going back an forth. When the car is in drive it is not as bad and it seemed a little better when it was warmer. I was thinking bad GAS, maybe adding the water did something???? or Maybe alternator going out? Any ideas
My car has been running awesome until today. Today on my way home I got gas and drove home, being a hot day when I pulled into my driveway I noticed the car was running a little above the 220 so I put some more water in the reservoir. Later on when I started the car the idle would fluctuate down to about 500 and the headlights would dim and the back up to 650 and keep going back an forth. When the car is in drive it is not as bad and it seemed a little better when it was warmer. I was thinking bad GAS, maybe adding the water did something???? or Maybe alternator going out? Any ideas
09-05-2004 | 11:53 AM
#2
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Joined: Jan 2000
Posts: 19,453
Likes: 242
89,
Welcome Aboard!
For now, I'd disregard the alternator theory. Low idle and extra load (from headlights) will generally cause a lower output voltage condition. That's to be expected. As long as the belt is tracking correctly and has tension, forget about that for now.
As for the fluctuating idle RPM, the fuel may have an effect, but the IAC and ECM should try to maintain idle RPM regardless of that. My first step would be to remove the intake bellows, clean the throttle body, and concentrate some spray through the IAC air passages. Once the throttle body is clean, one potential variable is eliminated. That doesn't mean that the IAC is clean enough to operate correctly, but should at least provide a clear passage for idle air.
See if that helps a bit. Use some care to keep the spray cleaner away from the TPS.
Welcome Aboard!
For now, I'd disregard the alternator theory. Low idle and extra load (from headlights) will generally cause a lower output voltage condition. That's to be expected. As long as the belt is tracking correctly and has tension, forget about that for now.
As for the fluctuating idle RPM, the fuel may have an effect, but the IAC and ECM should try to maintain idle RPM regardless of that. My first step would be to remove the intake bellows, clean the throttle body, and concentrate some spray through the IAC air passages. Once the throttle body is clean, one potential variable is eliminated. That doesn't mean that the IAC is clean enough to operate correctly, but should at least provide a clear passage for idle air.
See if that helps a bit. Use some care to keep the spray cleaner away from the TPS.
Last edited by Vader; 09-05-2004 at 12:00 PM.
09-05-2004 | 02:28 PM
#3
Thread Starter
Junior Member
Joined: Aug 2004
Posts: 78
Likes: 0
From: Orange County, CA
Car: 89 Trans AM GTA
Engine: 5.7L
Originally posted by Vader
89,
Welcome Aboard!
For now, I'd disregard the alternator theory. Low idle and extra load (from headlights) will generally cause a lower output voltage condition. That's to be expected. As long as the belt is tracking correctly and has tension, forget about that for now.
As for the fluctuating idle RPM, the fuel may have an effect, but the IAC and ECM should try to maintain idle RPM regardless of that. My first step would be to remove the intake bellows, clean the throttle body, and concentrate some spray through the IAC air passages. Once the throttle body is clean, one potential variable is eliminated. That doesn't mean that the IAC is clean enough to operate correctly, but should at least provide a clear passage for idle air.
See if that helps a bit. Use some care to keep the spray cleaner away from the TPS.
89,
Welcome Aboard!
For now, I'd disregard the alternator theory. Low idle and extra load (from headlights) will generally cause a lower output voltage condition. That's to be expected. As long as the belt is tracking correctly and has tension, forget about that for now.
As for the fluctuating idle RPM, the fuel may have an effect, but the IAC and ECM should try to maintain idle RPM regardless of that. My first step would be to remove the intake bellows, clean the throttle body, and concentrate some spray through the IAC air passages. Once the throttle body is clean, one potential variable is eliminated. That doesn't mean that the IAC is clean enough to operate correctly, but should at least provide a clear passage for idle air.
See if that helps a bit. Use some care to keep the spray cleaner away from the TPS.
Thanks I will try this
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