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This is what confuses me. My IAC is at zero with a warm engine. But my idle is not high. Here's a screen shot of datalogs. Checked and rechecked for vacuum leaks. Stock 93 LT1.
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I'd take the TB off and clean it completely. Clean all the passages, new gaskets and spray brake cleaner GENTLY on the IAC pintle. Reassemble and see what you get.
650 RPM @ idle. rules out a vacuum leak. have you cleaned and polished the IAC pintle lately. any codes? confirmed IAC voltage. Rare. possible IAC failure.
I'd take the TB off and clean it completely. Clean all the passages, new gaskets and spray brake cleaner GENTLY on the IAC pintle. Reassemble and see what you get.
IAC is new. I did clean the TB and the IAC passage.
Originally Posted by THE 383 admiral
650 RPM @ idle. rules out a vacuum leak. have you cleaned and polished the IAC pintle lately. any codes? confirmed IAC voltage. Rare. possible IAC failure.
No codes. Not sure how to confirm IAC voltage, but I will look in the FSM about that.
Originally Posted by MrWillys
Can you close the blade and make them rise?
Close the throttle cable manually? I doubt it. But will double check it tomorrow.
Close the throttle cable manually? I doubt it. But will double check it tomorrow.
The original TB has a stop screw that it rests on at idle. From the factory it came with a cap so it could not be adjusted. Most have been removed over the years and yours may have been opened. What is funny is you seem to have a stable idle.
Yes, the idle is pretty stable. Looks steady on the tach, no surge. Scan tool shows 550-600 rpm at warm idle, in drive. Park is 650 rpm. I looked at the throttle stop today. The metal cap looks like it has never been messed with. Will post pics tomorrow.
Go to an Autozone and borrow their scan tool. I shut everything but the motor off and in neutral, see what the IAC counts are. Also see what the ECM requested idle is.
Go to an Autozone and borrow their scan tool. I shut everything but the motor off and in neutral, see what the IAC counts are. Also see what the ECM requested idle is.
Will do. FSM says 550 rpm in gear, warm idle. Curious to see what the scanner says.
Curious to this as well. I know you've been hunting this one but you don't have any symptoms other than some odd data.
Yup been hunting it for a while. Car runs fine otherwise, just not so good mpg in the city. Spot on MPG in the freeway. Will find the cause, and let you guys know.
You can bend the tab that rests on the stop screw to change the "screw setting" without removing or disturbing the plug over the screw.
Bend it just a smidge, and see if you get some counts.
Why would you want to bend it? I understand that at times we have to perform some feats of "Ghetto Engineering" but a screw turn is less permanent than bending. Besides, perhaps you can partially block the IAC inlet with your finger and see if the counts climb.
Why would you want to bend it? I understand that at times we have to perform some feats of "Ghetto Engineering" but a screw turn is less permanent than bending. Besides, perhaps you can partially block the IAC inlet with your finger and see if the counts climb.
You know what happens when you bend it, don't you? After all is said and done you get the "Oh, ****" moment and you wished you didn't. I just had an ignition issue that I traced to the module. Replaced it and it still didn't work. Changed the pickup, no joy. Bought another module and life is good. Tested all 3 and 2 failed the test. The one that passed was the last purchase. The first replacement was new. Next time, I will test my spares before use. Obviously, warranty long expired.
hi op im no expert but here is what it looks like to me.
high fuel trim on left bank, bad fuel mileage in city but good on highway, closed iac, tells me u have unmetered air getting on left bank, small in size to the point of being irrellevant %wise at cruising fuel consumptions but big enough to affect stop and go fuel economy.
you say the car operates very good, id be checking the exhaust manifold or any plumbing btwn the O2 sensor and the exhaust manifold. on an L98, the check valves can let air in the air injection system after the manifold but before the O2 and result is the high blm reading because the ecu reads too much oxygen at the o2 sensor. it increases the fuel delivery which shows up as high blm, and car runs rich.
that said, having a 0count on the iac sounds like enough air is getting in to cause the o2 reading to cause the ecm to close the iac. but because you're saying the idle is fairly stabe, then id assume us at the exhaust.
only i say it is because i had that on my red 85 z51. it ran rich. then i found two missing bolts on the driver side exhaust manifold which is the side with the o2 on it.
Originally Posted by 1993C4LT1
This is what confuses me. My IAC is at zero with a warm engine. But my idle is not high. Here's a screen shot of datalogs. Checked and rechecked for vacuum leaks. Stock 93 LT1.
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IAC count at zero
Yup been hunting it for a while. Car runs fine otherwise, just not so good mpg in the city. Spot on MPG in the freeway. Will find the cause, and let you guys know.
