1985 Corvette Won't Idle
Thread Starter
Cruising
Joined: Sep 2023
Posts: 13
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From: NJ
1985 Corvette Won't Idle
Hello! I recently got a 1985 C4 and I've been having quite the problem trying to get this to idle. Since it had been sitting for a while (years) I did a major disassembly of the top part of the engine to clean some minor leaks caused by the gaskets.
I'n short I got new Injectors, EGR, pcv valve, took out the fuel pump and checked pressure (it holds it very well) cleaned the fuel tank, changed the fuel filter, changed gaskets and some vacuum lines.
However the car won't idle it starts right up but its like it wont accelerate on its own. Only stays on if I give it gas.
Its important to note that the car didn't idle before and still won't. If I disconnect the MAF sensor it still won't idle, or it may at times but rarely and will only hold it for about 20-30 seconds (with or without MAF connected) I haven't found any vacuum leaks, vacuum seems good but I'l get a smoke test going tomorrow.
Any clues? Thanks in advance
(The vibration sound In the video is the roof - is not screwed) https://www.youtube.com/watch?v=5PUBgsqaEB8
The forum wont let me attach the URL
I'n short I got new Injectors, EGR, pcv valve, took out the fuel pump and checked pressure (it holds it very well) cleaned the fuel tank, changed the fuel filter, changed gaskets and some vacuum lines.
However the car won't idle it starts right up but its like it wont accelerate on its own. Only stays on if I give it gas.
Its important to note that the car didn't idle before and still won't. If I disconnect the MAF sensor it still won't idle, or it may at times but rarely and will only hold it for about 20-30 seconds (with or without MAF connected) I haven't found any vacuum leaks, vacuum seems good but I'l get a smoke test going tomorrow.
Any clues? Thanks in advance
(The vibration sound In the video is the roof - is not screwed) https://www.youtube.com/watch?v=5PUBgsqaEB8
The forum wont let me attach the URL
Instructor
Joined: Jul 2023
Posts: 103
Likes: 109
Sounds like it's hard starting. Battery voltage low? Or is the timing too advanced?
pretty sure there's a base idle adjustment you have to make. You can Google it. Involves putting it into diagnostic mode and disconnecting the IAC. Been a long time since I messed with mid 80s GM fuel injection
pretty sure there's a base idle adjustment you have to make. You can Google it. Involves putting it into diagnostic mode and disconnecting the IAC. Been a long time since I messed with mid 80s GM fuel injection
Thread Starter
Cruising
Joined: Sep 2023
Posts: 13
Likes: 0
From: NJ
Sounds like it's hard starting. Battery voltage low? Or is the timing too advanced?
pretty sure there's a base idle adjustment you have to make. You can Google it. Involves putting it into diagnostic mode and disconnecting the IAC. Been a long time since I messed with mid 80s GM fuel injection
pretty sure there's a base idle adjustment you have to make. You can Google it. Involves putting it into diagnostic mode and disconnecting the IAC. Been a long time since I messed with mid 80s GM fuel injection
I'l also get to that too thenRegarding the battery is not related to that since its new and I also used a different one to no avail.
The timing, you mean the distribuitor? I know it must be turned 6° degrees but in relation to what? And to what side?
Thank you for the help! Il get back to this if something changes or not.
Instructor
Joined: Jul 2023
Posts: 103
Likes: 109
Timing is 6 degrees before top dead center. Your timing when the spark plug fires. You use a timing light while the engine is running to adjust it.
If you hold the engine at 1500 let's say, does the engine stay running?
If you hold the engine at 1500 let's say, does the engine stay running?
Thread Starter
Cruising
Joined: Sep 2023
Posts: 13
Likes: 0
From: NJ
I ran the smoke machine and actually found a vacuum leak in the lower intake gasket (the one made of rubber by the side of the distributor) I'l get going with fixing it, I wonder if this Is the cause of the lack of iddle. Must have come off while putting the intake back into position.
Thanks for the help!
Thread Starter
Cruising
Joined: Sep 2023
Posts: 13
Likes: 0
From: NJ
Figured I'd add this, the problem was finally fixed by also putting in a new MAF sensor, this solved the rough iddle.
Last edited by Vindkast; Nov 25, 2024 at 06:33 PM.
