High cold idle speed
Thread Starter
Drifting
Joined: Oct 2004
Posts: 1,384
Likes: 8
From: Southwest Virginia
High cold idle speed
Working on a friends 97 automatic with a high cold idle speed problem. Once the engine is warm the idle speed seems correct.
When first started, cold engine and 80 degree ambient temp the engine revs to around 2600 RPM for 3-4 seconds then drops to around 1200 RPM for a few seconds then drops to around 900 RPM. All that seem fairly normal. The problem is as soon as the trans goes in to gear (reverse or drive) the idle goes to around 2500 RPM, as soon as you let off the brake your head goes back and your on your way quite quickly. This thing will cruse over 35 MPH on flat ground without touching the pedal. Till the engine warms up you have to drive around with your foot on the brake.
When idling down the road you can put the car in neutral and the engine will idle between 1200 RPM and 2200 RPM but when the car comes to a stop the idle will drop to around 900 RPM.
Mods appear to be shorty headers, adjustable fuel pressure regulator, and air bridge.
No related codes set. A fuel pressure check showed 50psi, I adjusted to 60psi, seems to helped the driveability and mileage but no change on idle. No vacuum leaks found, PCV system seems to be working correctly. Cleaned the throttle plate and body.
First thought was someone had screwed with the tune, but reading the tune and comparing to a factory tune downloaded from holdencrazy.com showed no difference.
Using FlashScan shows the true engine speed much higher than the desired idle speed when cold and in gear.
Anyone got any ideas?
When first started, cold engine and 80 degree ambient temp the engine revs to around 2600 RPM for 3-4 seconds then drops to around 1200 RPM for a few seconds then drops to around 900 RPM. All that seem fairly normal. The problem is as soon as the trans goes in to gear (reverse or drive) the idle goes to around 2500 RPM, as soon as you let off the brake your head goes back and your on your way quite quickly. This thing will cruse over 35 MPH on flat ground without touching the pedal. Till the engine warms up you have to drive around with your foot on the brake.
When idling down the road you can put the car in neutral and the engine will idle between 1200 RPM and 2200 RPM but when the car comes to a stop the idle will drop to around 900 RPM.
Mods appear to be shorty headers, adjustable fuel pressure regulator, and air bridge.
No related codes set. A fuel pressure check showed 50psi, I adjusted to 60psi, seems to helped the driveability and mileage but no change on idle. No vacuum leaks found, PCV system seems to be working correctly. Cleaned the throttle plate and body.
First thought was someone had screwed with the tune, but reading the tune and comparing to a factory tune downloaded from holdencrazy.com showed no difference.
Using FlashScan shows the true engine speed much higher than the desired idle speed when cold and in gear.
Anyone got any ideas?
Tech Contributor
Joined: Jan 2007
Posts: 19,115
Likes: 1,038
From: Dyer, IN
Working on a friends 97 automatic with a high cold idle speed problem. Once the engine is warm the idle speed seems correct.
When first started, cold engine and 80 degree ambient temp the engine revs to around 2600 RPM for 3-4 seconds then drops to around 1200 RPM for a few seconds then drops to around 900 RPM. All that seem fairly normal. The problem is as soon as the trans goes in to gear (reverse or drive) the idle goes to around 2500 RPM, as soon as you let off the brake your head goes back and your on your way quite quickly. This thing will cruse over 35 MPH on flat ground without touching the pedal. Till the engine warms up you have to drive around with your foot on the brake.
When idling down the road you can put the car in neutral and the engine will idle between 1200 RPM and 2200 RPM but when the car comes to a stop the idle will drop to around 900 RPM.
Mods appear to be shorty headers, adjustable fuel pressure regulator, and air bridge.
No related codes set. A fuel pressure check showed 50psi, I adjusted to 60psi, seems to helped the driveability and mileage but no change on idle. No vacuum leaks found, PCV system seems to be working correctly. Cleaned the throttle plate and body.
First thought was someone had screwed with the tune, but reading the tune and comparing to a factory tune downloaded from holdencrazy.com showed no difference.
Using FlashScan shows the true engine speed much higher than the desired idle speed when cold and in gear.
Anyone got any ideas?
When first started, cold engine and 80 degree ambient temp the engine revs to around 2600 RPM for 3-4 seconds then drops to around 1200 RPM for a few seconds then drops to around 900 RPM. All that seem fairly normal. The problem is as soon as the trans goes in to gear (reverse or drive) the idle goes to around 2500 RPM, as soon as you let off the brake your head goes back and your on your way quite quickly. This thing will cruse over 35 MPH on flat ground without touching the pedal. Till the engine warms up you have to drive around with your foot on the brake.
When idling down the road you can put the car in neutral and the engine will idle between 1200 RPM and 2200 RPM but when the car comes to a stop the idle will drop to around 900 RPM.
Mods appear to be shorty headers, adjustable fuel pressure regulator, and air bridge.
No related codes set. A fuel pressure check showed 50psi, I adjusted to 60psi, seems to helped the driveability and mileage but no change on idle. No vacuum leaks found, PCV system seems to be working correctly. Cleaned the throttle plate and body.
First thought was someone had screwed with the tune, but reading the tune and comparing to a factory tune downloaded from holdencrazy.com showed no difference.
Using FlashScan shows the true engine speed much higher than the desired idle speed when cold and in gear.
Anyone got any ideas?
Thread Starter
Drifting
Joined: Oct 2004
Posts: 1,384
Likes: 8
From: Southwest Virginia
Conditions to set high idle code:
ECT is greater than 60°C (140°F)
Vehicle speed is less than 1 mph
APP Indicated Angle is 0%
Idle speed is above the desired RPM
Conditions exist for 5 seconds
The actual idle speed is 200 RPM greater than the desired idle speed Action
So they don't seem to even check or alert on a cold engine, once warm it acts pretty good. Also they only seem to check when the vehicle is stopped. If stopped in neutral or park this one idles down to around 900. As soon as it is put in gear it seems to throttle up excessively high. In gear the transmission is holding the engine speed down when stopped but I'm guessing it is over 200 RPM above desired but I don't thing the temp will let the code be set. Have not watched the Accelerator Pedal Position (APP) Sensor on the scanner yet, need to do that.
Thread Starter
Drifting
Joined: Oct 2004
Posts: 1,384
Likes: 8
From: Southwest Virginia
The tune seems to compare to a factory tune so I don't think it has ever been tuned.
The IAT and ECT sensors do seem to read correct values.
Last edited by SpeedyZ; Sep 23, 2010 at 10:10 AM.
Thread Starter
Drifting
Joined: Oct 2004
Posts: 1,384
Likes: 8
From: Southwest Virginia
Not that I can find. Of course you can't see anything under the back of the intake, I have tried looking with a Snap-On remote camera on a cord but could not tell anything. Next step may be to pull the intake so I can see whats going on back there.
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