Hi Idle!

[compyelc4]

Hi Idle!

I have a slight problem and could use some advise.

I have a highly-babied '95 with 48k miles. She runs strong and sets no codes. Here is the problem: Every once in a while on a cold start she'll start on the first revolution and goes to normal high-idle until she warms up. This usually take about 5 minutes in warm weather. As I'm waiting at the first stoplight I notice the idle is about 200 RPM too high. High enough that I have to press on the brake just slightly more than usual to hold it still. Goosing the gas pedal a few times does not lower the RPM to its normal 650 RPM as we used to do with carb. engines. A couple of times I've gotten out, opened the hood and "tweaked" the throttle cam a little and even tried pushing the throttle plate toward the stop but this does not help. The only thing that helps, and this is 100% of the time, is to shut her down and restart. It then goes to normal. Any clues about this other than cleaning the throttle body which I have not done in about 20k miles? I'm thinking it may be mechanical but maybe electrical. Reminder: no codes and idle, normally, is just fine.

Thanks

 

[Hib Halverson]

I'd consult the service manual's troubleshooting info in re: rough or unstable idle.

You can try removing the IAC and cleaning its pintle and seat but do not imerse the IAC in solvent. A problem IAC is one of many causes of unstable idle.

 

[Schrade]

IAC, TPS, or carbon behind butterfly.

 

[compyelc4]

Thanks guys. I'll check out these sources and report back.

 

[tmkassin]

Thanks guys. I'll check out these sources and report back.

You might want to look for a vacuum leak too.

 

[compyelc4]

tmkassin,

Thanks for your suggestion too. My question to you is: I know a a vacuum leak could bring on high idle but 1) I think that would be a high idle all the time. Mine is only sometimes. and 2) upon restart my idle goes to normal. Wouldn't a vacuum leak react differently?

 

[tmkassin]

I will look in my FSM tomorrow. It could be tied to a relay that resets when you restart the motor.

 

[compyelc4]

tmkassis-

Thanks. I would really appreciate that.

 

[tmkassin]

Hi I brought my FSM home tonight to try to look up how to test your vacuum lines. The test is in volume 2 and I only brought volume 1. It is called Air Management Functional Test. I will have more details tomorrow.

 

[compyelc4]

tmkassin-

You are too much. I thank you and would do that for someone else if I could.

Thanks again.

PS- I do have a vacuum gauge and know how to use it so the info will be quite helpful.

 

[Schrade]

tmkassin,

Thanks for your suggestion too. My question to you is: I know a a vacuum leak could bring on high idle but 1) I think that would be a high idle all the time. Mine is only sometimes. and 2) upon restart my idle goes to normal. Wouldn't a vacuum leak react differently?

Vacuum leak makes idle lope like a Duncan yo-yo. 30 year old lawnmower, or a new car on the lot - same loping idle. Vacuum leak will NOT steady idle.

Steady high idle could be TPS...

 

[tmkassin]

Vacuum leak makes idle lope like a Duncan yo-yo. 30 year old lawnmower, or a new car on the lot - same loping idle. Vacuum leak will NOT steady idle.

Steady high idle could be TPS...

There are several pages I would like to send you. Do you have access to a fax?

 

[Schrade]

There are several pages I would like to send you. Do you have access to a fax?

You can email it if you want - I think it's active in my profile. If it's FSM stuff, post up the sections/numbers - I got mine here, and they're pretty similar for LT1. If a vac leak makes a steady high idle, I wanna' see this...

I just changed my email to 'visible', so however you want. But post it up; if I'm wrong, won't be the first time (or last).

 

[compyelc4]

tmkassin-

Thanks. Try this fax: 937/259-7867. That's my work fax. Please let me know when you fax so I won't be checking the fax every 5 minutes.

 

[tmkassin]

tmkassin-

Thanks. Try this fax: 937/259-7867. That's my work fax. Please let me know when you fax so I won't be checking the fax every 5 minutes.

I will send it tomorrow morning

 

[Schrade]

You can email it if you want - I think it's active in my profile. If it's FSM stuff, post up the sections/numbers - I got mine here, and they're pretty similar for LT1. If a vac leak makes a steady high idle, I wanna' see this...

I just changed my email to 'visible', so however you want. But post it up; if I'm wrong, won't be the first time (or last).

I'm hopin' to see this too here...

 

[tmkassin]

Message to Schrade. Why does it say "Banned" Under your name? Look on page 6E3-B-13. IAC operation. This controls vacuum. A vacuum leak doesn't always cause a loping issue. Try not to be so antagonistic.

 

[Schrade]

I was lookin' at that very page last night - 'Incorrect idle' (the first 2; rough, or unstable, sure ain't gonna' be 'steady high' idle). And then the 'definition' below that is "Engine runs unevenly at idle..."

I don't see how IAC could account for a high steady idle. It says if it's unplugged and reconnected while running, it might be wrong. It says re-set (re-calibration) takes 5 seconds to figure that out, or it will re-learn the proper calibration in a few drive cycles. That's a GOOD IAC. If the pintle spring is broken, I don't think it's gonna' be a steady idle - low, OR high... HibH said it could cause 'unstable' idle. I don't think ANY vacuum leak will make a steady idle.

If I'm wrong, I wanna' know it. With proof. A dull knife isn't a knife - it's a saw. And saws make a mess. Knives cut clean, and gettin' 'em sharp is gonna' generate some heat... It says BANNED from CF for tryin' to cut through the 'stuff', and sharpen the blade in the process.

 

[G Winter]

I was lookin' at that very page last night - 'Incorrect idle' (the first 2; rough, or unstable, sure ain't gonna' be 'steady high' idle). And then the 'definition' below that is "Engine runs unevenly at idle..."

I don't see how IAC could account for a high steady idle. It says if it's unplugged and reconnected while running, it might be wrong. It says re-set (re-calibration) takes 5 seconds to figure that out, or it will re-learn the proper calibration in a few drive cycles. That's a GOOD IAC. If the pintle spring is broken, I don't think it's gonna' be a steady idle - low, OR high... HibH said it could cause 'unstable' idle. I don't think ANY vacuum leak will make a steady idle.

If I'm wrong, I wanna' know it. With proof. A dull knife isn't a knife - it's a saw. And saws make a mess. Knives cut clean, and gettin' 'em sharp is gonna' generate some heat... It says BANNED from CF for tryin' to cut through the 'stuff', and sharpen the blade in the process.

Pull a vacuum hose off and see what happens.... high steady idle. Isn't that a vacuum leak ? It seems to me the IAC is a controlled leak.

Glenn

 

[Schrade]

Pull a vacuum hose off and see what happens.... high steady idle.

Glenn

No. Not steady. Loping only.