Idle Oddity - Opinions - Vader?
06-10-2001, 10:24 PM
#1
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Car: 86 T/A
Engine: 5.0 TPI
Transmission: 700R4
Idle Oddity - Opinions - Vader?
Vader and others I need an opinion here. Car runs great, no codes. On start up idle sets at about 1500 for say ... 6 or 7 seconds before dropping to a reasonable level. This is only a problem on startup in park as I sometimes have a habit of starting up, putting into gear and "thunk" ... too high of RPM.
When I'm driving and stop at a light the idle RPM under load is really no big deal, but on start I have to wait until it kicks down before engaging.
I'm thinking an IAC problem but I don't really know what steps to take to correct it. IAC is clean.
thanks........
When I'm driving and stop at a light the idle RPM under load is really no big deal, but on start I have to wait until it kicks down before engaging.
I'm thinking an IAC problem but I don't really know what steps to take to correct it. IAC is clean.
thanks........
06-11-2001, 09:31 AM
#2
Supreme Member
Mike, I don't think you have a problem, what you describe (if I'm understanding the post correctly) has occured on my car since new, even after 2 factory EPROM upgrades and a try with an ADS chip.
I keep meaning to plug in my scanner some day to look at the CTS reading vs. IAC counts, because when I had my intake apart last year, I cleaned my CTS and noticed the "problem?" subsided some...i/e when the engine would startup when it was already warmed up, the RPMs would go to 1600 or so, then down lower, after cleaning the CTS the warm-start RPM's did not exceed 1200-1250 for a month or so. Then back to "normal".
I spoke with a friend of my Dads who used to work at GM and he had told me that it's was possible that the coolant in the intake manifold had cooled down enough, or that it may not have been in contact with the CTS, during the start up...then the CTS would report that I was starting up a cooler/cold motor...I dunno.
When I get the topend of my engine back together and the car running, I'll plug in and see.
I keep meaning to plug in my scanner some day to look at the CTS reading vs. IAC counts, because when I had my intake apart last year, I cleaned my CTS and noticed the "problem?" subsided some...i/e when the engine would startup when it was already warmed up, the RPMs would go to 1600 or so, then down lower, after cleaning the CTS the warm-start RPM's did not exceed 1200-1250 for a month or so. Then back to "normal".
I spoke with a friend of my Dads who used to work at GM and he had told me that it's was possible that the coolant in the intake manifold had cooled down enough, or that it may not have been in contact with the CTS, during the start up...then the CTS would report that I was starting up a cooler/cold motor...I dunno.
When I get the topend of my engine back together and the car running, I'll plug in and see.
06-11-2001, 10:18 PM
#3
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Car: 86 T/A
Engine: 5.0 TPI
Transmission: 700R4
It just doesn't feel right. I feel like I'm about to drop the tranny. I help a friend at his car lot and I hop in and move cars around all day long. Mine is the only car that acts like this. I'm wondering if the IAC stepping motor is out of whack or something.
06-11-2001, 11:17 PM
#4
Supreme Member
Ah, I see, you're not waiting for it to idle down? Or are you saying it doesn't idle down?
See, I always let mine idle down to normal idling RPM's (~750), before I put it in gear. If you're putting it in gear at 1200 or so, you're going to short live the U-joints at the least.
You ought to see the pissed look on peoples faces in parking lots waiting for my space, and behind me at gas stations when I first start it up....could be 15 seconds or 30 seconds, depending on how she feels that day
See, I always let mine idle down to normal idling RPM's (~750), before I put it in gear. If you're putting it in gear at 1200 or so, you're going to short live the U-joints at the least.
You ought to see the pissed look on peoples faces in parking lots waiting for my space, and behind me at gas stations when I first start it up....could be 15 seconds or 30 seconds, depending on how she feels that day
06-12-2001, 08:10 AM
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Car: 86 T/A
Engine: 5.0 TPI
Transmission: 700R4
Exactly. It's not really that I'm not waiting for idle down. It's taking too dang long to idle down. It's not right. If it's by design then it's a flaw. It's not like I jump in and slam into gear... I treat it like any other auto tranny or any other car.
It is a problem in "Park" or "Neutral". When I'm at a stop sign in gear, brake on, it may be doing the same thing but the load naturally brings it down. And it's not a big deal in the morning to wait because I always let my car warm up..... BUT.... say you run into a store or sitting in a line, it is always on start-up or re-start and it just seems like an usually long time to drop to the 750. Since it is in "steps" makes me think IAC.
Anybody else having this problem besides Mike and I? Vader where the heck are you.....LOL.
It is a problem in "Park" or "Neutral". When I'm at a stop sign in gear, brake on, it may be doing the same thing but the load naturally brings it down. And it's not a big deal in the morning to wait because I always let my car warm up..... BUT.... say you run into a store or sitting in a line, it is always on start-up or re-start and it just seems like an usually long time to drop to the 750. Since it is in "steps" makes me think IAC.
Anybody else having this problem besides Mike and I? Vader where the heck are you.....LOL.
06-12-2001, 01:28 PM
#6
Mike,
I've had teh same symptoms for years. The IAC stepper is controlled by the ECM, and the ECM won't step down the pintle position until it is certain that the CTS is warmed enough. It's a slow process.
If you feel yours is a little slower-reacting that it used to be, you could lightly lube the IAC pintle rack gear, and make sure the CTS is not covered in scale and slime so that it reacts as quickly as possible to temperature changes.
Aside from that, the car is designed to idle high at first start then step down in increments to the target idle. I'm not sure how to program around this, or if you'd want to.
------------------
Later,
Vader
------------------
"Let the bodies hit the floor!"
Adobe Acrobat Reader
I've had teh same symptoms for years. The IAC stepper is controlled by the ECM, and the ECM won't step down the pintle position until it is certain that the CTS is warmed enough. It's a slow process.
If you feel yours is a little slower-reacting that it used to be, you could lightly lube the IAC pintle rack gear, and make sure the CTS is not covered in scale and slime so that it reacts as quickly as possible to temperature changes.
Aside from that, the car is designed to idle high at first start then step down in increments to the target idle. I'm not sure how to program around this, or if you'd want to.
------------------
Later,
Vader
------------------
"Let the bodies hit the floor!"
Adobe Acrobat Reader
06-13-2001, 07:15 AM
#7
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Car: 86 T/A
Engine: 5.0 TPI
Transmission: 700R4
thanks guys.... that is what I will do. I cleaned the heck out of the IAC so maybe I left it a bit dry in my code 44 search days.
ONE of the items I didn't replace on this car was the CTS. I'll do both and that way I'll know that it's as good as it can get.
..appreciate it
ONE of the items I didn't replace on this car was the CTS. I'll do both and that way I'll know that it's as good as it can get.
..appreciate it
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