LT1 Idle is too high...1993
05-01-2010, 04:21 AM
#21
Le Mans Master
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St. Jude Donor '03 & '05
I took the air cleaner assmbley off and put my hand over the IAC port while running at the rpms came down and engine ran good, so I am pretty positive it is bad, knock on wood.
I also need to verify power to the IAC.
05-01-2010, 04:42 AM
#22
Safety Car
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Keep at it.........
I doubt this is your problem but TPIS makes a IAC housing I'm going to try. Mine looks a little worn in the seat. Also, theirs doesn't have all the cooling veins in it like the OE one either. Good luck!
I doubt this is your problem but TPIS makes a IAC housing I'm going to try. Mine looks a little worn in the seat. Also, theirs doesn't have all the cooling veins in it like the OE one either. Good luck!
05-01-2010, 09:47 AM
#24
Race Director
Okay, to make a long story short. No vacuum leaks, no DTC's, heated O2's with long tubes. Engine ran sweet about three weeks ago. Came back from TAD, now it wont idle below 1400 rpm. Turn AC on it goes down. O2's are working fine using my scan tool.
I sprayed bubbly water over all hoses etc and nothing changed. No exhaust leaks. Cleaned the living heck out of the throttle body and IAC housing.
IAC is very clean, and I didnt clean it as it is a couple years old.
I checked the pins for resistance and the IAC is within specs. I also connected it and put it in a bag and turned the key on, NOTHINg, it didnt move at all. So, being a 93, I pulled the spring down and turned the IAC out and in for several test to see if it would move. Nothing.
I then put it back in the throttle body at 1", 1 1/8", and 1 3/16 " without the connector and the idle changed, got higher as I went shorter and at 1 3/16 it was at 1100. (My engine chip is set for 850, and I also tried three different older tunes that worked prior to all this and the idle never changed).
So, I reconnected IAC connector, started it up and no change, turned ac on and it brought it down 200rpm.
Took it out and it didnt change length.
Should it change length when it was out and connected and I turn the key on? Should it have changed length within the engine when running and ac turned on?
Can an IAC be bad, yet show its resistance reading being good?
I sprayed bubbly water over all hoses etc and nothing changed. No exhaust leaks. Cleaned the living heck out of the throttle body and IAC housing.
IAC is very clean, and I didnt clean it as it is a couple years old.
I checked the pins for resistance and the IAC is within specs. I also connected it and put it in a bag and turned the key on, NOTHINg, it didnt move at all. So, being a 93, I pulled the spring down and turned the IAC out and in for several test to see if it would move. Nothing.
I then put it back in the throttle body at 1", 1 1/8", and 1 3/16 " without the connector and the idle changed, got higher as I went shorter and at 1 3/16 it was at 1100. (My engine chip is set for 850, and I also tried three different older tunes that worked prior to all this and the idle never changed).
So, I reconnected IAC connector, started it up and no change, turned ac on and it brought it down 200rpm.
Took it out and it didnt change length.
Should it change length when it was out and connected and I turn the key on? Should it have changed length within the engine when running and ac turned on?
Can an IAC be bad, yet show its resistance reading being good?
05-01-2010, 04:17 PM
#26
Race Director
You may be right about the usage deal I haven't used the AC since last summer.
Good luck Brother .....I believe a little holy water is in order for your car....it may knock some of demons out of your ride.
Mike
05-01-2010, 04:24 PM
#27
Le Mans Master
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St. Jude Donor '03 & '05
Is the IAC getting a signal? I bought an American made IAC at AUTOZONE last week, they actually had it on the shelf. My car was running sweet and idling like normal (IAC actually moved) however, it would not idle with the AC running ....after cleaning TB and IAC ports I gave up and bought new IAC now it will idle in gear with the AC running (again).
You may be right about the usage deal I haven't used the AC since last summer.
Good luck Brother .....I believe a little holy water is in order for your car....it may knock some of demons out of your ride.
Mike
You may be right about the usage deal I haven't used the AC since last summer.
Good luck Brother .....I believe a little holy water is in order for your car....it may knock some of demons out of your ride.
Mike
Now with it idleing at 1400 it only bring down the rpms 200 when ac is on. But, I have it programmed to go up 50 rpms with ac on. So, it isnt doing anything IMHO.
I am wondering how I do tell the IAC is getting a signal. I know its a pulsed signal, but no one has ever wrote about that.
I need more than Holy Water, I need the man himself to come here and bless it!
I did order an AC Delco, should be here in a few days.
I cant get them for less than a 100 bucks here on island. Got it cheaper with shipping off island. Crazy Hawaii tax.
05-01-2010, 04:26 PM
#28
Race Director
Hey Mike, the one that is in there is a cheapo one from Checkers. It was able to idle in gear with AC.
Now with it idleing at 1400 it only bring down the rpms 200 when ac is on. But, I have it programmed to go up 50 rpms with ac on. So, it isnt doing anything IMHO.
I am wondering how I do tell the IAC is getting a signal. I know its a pulsed signal, but no one has ever wrote about that.
I need more than Holy Water, I need the man himself to come here and bless it!
I did order an AC Delco, should be here in a few days.
I cant get them for less than a 100 bucks here on island. Got it cheaper with shipping off island. Crazy Hawaii tax.
Now with it idleing at 1400 it only bring down the rpms 200 when ac is on. But, I have it programmed to go up 50 rpms with ac on. So, it isnt doing anything IMHO.
I am wondering how I do tell the IAC is getting a signal. I know its a pulsed signal, but no one has ever wrote about that.
I need more than Holy Water, I need the man himself to come here and bless it!
I did order an AC Delco, should be here in a few days.
I cant get them for less than a 100 bucks here on island. Got it cheaper with shipping off island. Crazy Hawaii tax.
(I attended Aikahi Elementary, Kailua Intermediate and Kalaheo High) However, I'd try the holy water and I used to get my bike blessed, you probably should try for a Corvette blessing if the holy water doesn't work.
Mike
Last edited by aboatguy; 05-01-2010 at 04:41 PM.
05-02-2010, 05:38 PM
#30
Steve, I encountered the same problems you are seeing with your idle. I swapped a few parts over the winter on my engine a few years back and so the engine hadn't been running for about 4 months. It just wouldn't idle correctly. When I turned the AC on it would die on me. I reset the IAC so many times, the resistance was also good but only a new IAC brought my idle back to where it should be.
Swap your IAC and you'll be good.
Swap your IAC and you'll be good.
05-02-2010, 05:57 PM
#31
Le Mans Master
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St. Jude Donor '03 & '05
When I get the new one, and if it fixes it I will take the old one apart to see how fragile these are. I bet the heat and carbon are brutal on these plastic gears.
07-19-2010, 04:49 PM
#37
Instructor
IAC pintle needs to be under 1 1/8" and check for a leak at the MAP sensor. I had one there once, drove me crazy trying to find that one.
Check for a leak at the power booster, I have a leak there now.
FSM says to check:
PCV operation
IAC
MAP
EGR
Check A/C operation, if ECM thinks A/C is on, it will raise the idle.
Crankcase ventilation, i.e. tube running from pass. side valve cover to TB
PNP switch circuit, Park/neutral switch.
AIR system
Altenator putting out > 16v or < 9v
EVAP system - see my post about this
O2's
leaking FI
fuel in FPR
Leaking exhaust manifold
This should keep you busy for a while!!
Check for a leak at the power booster, I have a leak there now.
FSM says to check:
PCV operation
IAC
MAP
EGR
Check A/C operation, if ECM thinks A/C is on, it will raise the idle.
Crankcase ventilation, i.e. tube running from pass. side valve cover to TB
PNP switch circuit, Park/neutral switch.
AIR system
Altenator putting out > 16v or < 9v
EVAP system - see my post about this
O2's
leaking FI
fuel in FPR
Leaking exhaust manifold
This should keep you busy for a while!!
Hey Surfer92, how in the world did you manage to hunt down a vacuum leak at your MAP sensor?!!
I would think that would be almost impossible to find.
07-20-2010, 05:01 AM
#38
Le Mans Master
05-01-2019, 09:45 AM
#39
Safety Car
I had this problem after I installed new wires. I was searching everywhere to figure out how to fix the idle with all kinds of complex fixes and computer programs. Then I looked and saw that one of the throttle body pigtail wires had been broken somewhere along the line. That was easy.
-- Joe
