Weird Idle Problem on 94
Thread Starter
Melting Slicks
Joined: Feb 2005
Posts: 3,204
Likes: 4
From: Midland Georgia
St. Jude Donor '06
Weird Idle Problem on 94
I have a 94 LT-1 with the following mods:
Hooker Long tube headers.
Lt4 Hotcam.
Tom Wong PCM programmed for the above mods.
Emissions removed!
Just installed new MSD spark plug wires.
The problem I am having is this:
I come off of a interstate exit ramp and come to a stop and the cars idle drops to 500 rpms and almost dies. Then it will bump itself up to 750 to 800 rpms and everything is fine. (Before the new plug wires it would die but would easily restart but I had to goose the throttle to about 1200 rpms to keep it running.
Any ideas?
Hooker Long tube headers.
Lt4 Hotcam.
Tom Wong PCM programmed for the above mods.
Emissions removed!
Just installed new MSD spark plug wires.
The problem I am having is this:
I come off of a interstate exit ramp and come to a stop and the cars idle drops to 500 rpms and almost dies. Then it will bump itself up to 750 to 800 rpms and everything is fine. (Before the new plug wires it would die but would easily restart but I had to goose the throttle to about 1200 rpms to keep it running.
Any ideas?
Intermediate
Joined: Oct 2005
Posts: 39
Likes: 1
From: Casa grande Arizona
I know im new here but i seem to see alot of people with complaints about timing and the idle of the vettes since i just bought mine I really dont know much about them, should i expect this in the future? is this a normal problem with all vettes or just ones that have been modified
Thread Starter
Melting Slicks
Joined: Feb 2005
Posts: 3,204
Likes: 4
From: Midland Georgia
St. Jude Donor '06
Yup
I think it happens to everyone. Just new guys like us have to learn to fix it... A little effort tuning and tweeking these jewels payoff with the drives! 
Safety Car
Joined: Dec 2002
Posts: 3,655
Likes: 24
From: Charleston SC
Two thoughts here a lazy or dirty IAC valve or the IAC not set correctly. Have you killed the battery lately? I have had to reset the IAC before after disconnecting the battery. This tec tip should help. When performing the IAC reset procedure it some times takes two or three times to be perfect.
https://www.corvetteforum.com/techti...D=94&TopicID=2
https://www.corvetteforum.com/techti...D=94&TopicID=2
Le Mans Master
Joined: May 2005
Posts: 7,348
Likes: 2,272
From: Central Maryland
Originally Posted by 94azvette
that being said, what would you say is the best way to learn all the little tricks? reading or by doing?
I'd also highly recommend you order a set of the Factory Service Manuals for your C4. They will be invaluable when you are doing any work on your car.
And there's just no substitute for hands-on experience. But, I'd suggest you learn as much as you can about what you're trying to accomplish before you go charging headlong into any service work. \
Be well,
SJW
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Melting Slicks
Joined: Oct 2004
Posts: 2,510
Likes: 4
From: Austin Texas
I had a similar idle problem before where the engine would idle very low, almost to the point of quitting, and then adjust itself, and the idle would pick up. But with my condition, the "SES" dummy light would illuminate during the low stumbling idle, and then go out when the computer corrected the idle. Turned out to be a bad O2 sensor. This idle "correction" was the ECM disregarding the O2 voltage output and switching to a "lookup table" to determine AFR. I dumped the codes, replaced the faulty O2 sensor, and problem resolved.
1) Did you notice your "SES" light turn on momentarily while the idle was low?
2) Did you check to see if there are any error codes stored in computer?
1) Did you notice your "SES" light turn on momentarily while the idle was low?
2) Did you check to see if there are any error codes stored in computer?
Le Mans Master
Joined: May 2005
Posts: 5,214
Likes: 65
From: Queensland, AUSTRALIA
Originally Posted by Drivn2Fast
clean the IAC/Throttle and run some seafoam or your favorite top engine decarbonizer through it and you should be good.
Dave
Dave
Pull the throttle body off, pull the whole thing apart, clean it all, especially around the edges of the throttle plates and the IAC tip, the entire IAC path, and where the tip seats in the base. I just did mine and it made the world of difference. Its not hard, its only 4 bolts to remove it. I also wouldnt discount the fact the 02 sensor might be on its way out, but i doubt it if you dont have a code for it. Does your SERVICE ENGINE SOON light come on when you first start the car?
Thread Starter
Melting Slicks
Joined: Feb 2005
Posts: 3,204
Likes: 4
From: Midland Georgia
St. Jude Donor '06
Iac?
I will pull the throttle body off and give that a try frist. Starting to get this car right and it is just nasty out there today. But that is the nice thing about living in Georgia (USA baby!) The sun will be out and it will be 60 degrees on Thanksgivng and I am going for a nice "Turkey Trot" drive before dinner!
Thanks to all! I will let you know. Man I love this forum.
By the way I have the red service manuals (2 volume sets) and can't find "IAC" in the index. Why is that?
94 LT-1 Coupe.
Thanks to all! I will let you know. Man I love this forum.
By the way I have the red service manuals (2 volume sets) and can't find "IAC" in the index. Why is that?
94 LT-1 Coupe.
Le Mans Master
Joined: May 2005
Posts: 5,214
Likes: 65
From: Queensland, AUSTRALIA
IAC is Idle Air Controller, also known as Stepper Motor. On the 94 it is in the same position as all other LT1s/L98s, which is bottom right of the throttle body and held in place by 2 TORX screws. When removing the throttle body, its very easy, but first undo all the electrical contectors on the right hand side, as well as 2 rubber hoses on the upper right hand side(1 goes to the right rocker cover, the other goes to a little black thing with a red plug on the side of the manifold). Dont do the coolant ones yet, undo the 4 bolts that hold it to the intake manifold, and if youre careful enough when doing this you will be able to re-use the gaskets. Undo the coolant line when you have pulled the throttle body as far towards the front of the car as you can, so you dont spill coolant near the OPTIspark unit. If you dont have the throttle body coolant by-pass, now is the perfect time to do it. All you need is 2 hose clamps and a straight joiner pipe. When you have it off the car, remove the IAC, then remove the bottom piece, clean that and the IAC point very thoroughly. Then clean the rest of the throttle body, remove the top plate and clean under that. Make it look just like new. Installation is reverse of removal.
Thread Starter
Melting Slicks
Joined: Feb 2005
Posts: 3,204
Likes: 4
From: Midland Georgia
St. Jude Donor '06
Thanks
Thanks "Case"
Last thing in the world I thought I would get would be repair advise from an Aussie with a right hand drive corvette!? Dang forum is great. 
I looked at my manual again last night and found the IAC under the throttle body section. Thanks for the advise. BTW What does the coolant bypass do?
Thanks Mate!
Last thing in the world I thought I would get would be repair advise from an Aussie with a right hand drive corvette!?
Dang forum is great. I looked at my manual again last night and found the IAC under the throttle body section. Thanks for the advise. BTW What does the coolant bypass do?Thanks Mate!
Le Mans Master
Joined: May 2005
Posts: 5,214
Likes: 65
From: Queensland, AUSTRALIA
Originally Posted by jakers
Thanks "Case"
Last thing in the world I thought I would get would be repair advise from an Aussie with a right hand drive corvette!? Dang forum is great. I looked at my manual again last night and found the IAC under the throttle body section. Thanks for the advise. BTW What does the coolant bypass do?
Thanks Mate!
Last thing in the world I thought I would get would be repair advise from an Aussie with a right hand drive corvette!?
Dang forum is great. I looked at my manual again last night and found the IAC under the throttle body section. Thanks for the advise. BTW What does the coolant bypass do?Thanks Mate!
