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Help! Cannot get it tuned to idle — knocks when I accelerate from low rpm's…

brewster1943

New member
Joined
Nov 7, 2016
Messages
3
Location
Edmond, Oklahoma
Corvette
1987 Blue Convertible
My 1987 vette ran perfectly until one evening at 7-11 it just stopped. Finally got it home and pulled the distributor cap. Found plastic parts almost shredded, so I cleaned it out and replaced the ignition regulator and other parts inside the distributor. Would not start. And that's when the headaches began.
New distributor, cap and coil. I've replaced the throttle sensor, have new plugs and wired, but to no avail. When I start it cold, it will not idle until the coolant reaches at least 160 degrees. I have to play the throttle to keep it running until it gets to that temp, all the while belching and backfiring. Once it it there, it will idle but the idle speed ranged from 500 to 800 rpms. Once I have the engine up to around 1600 or 1800 rpms, it seems to run smoothly. I've adjusted the timing, set the throttle sensor to the correct voltage, plugged all the wires back in, and still have the problems.
My next step is to replace the IAC. My question is: do my car's symptoms sound like a bad IAC? And second, can the IAC be replaced (removed and a new one installed) without taking the throttle body off? I don't see any way to do it, but thought someone might know a way. Any advice would be appreciated!
 

hcbph

Well-known member
Joined
Aug 30, 2013
Messages
260
Location
Minneapolis, Mn.
Corvette
86 Red Convertible
I'm interested in the IAC replacement too. I had some issues with mine, but it was intermittent. When it happened the car barely ran till it was warmed up.

In my case, when it happened, if I shut it off and let it set a little on restart it was fine. Another was it went away when I took a plastic faced hammer and rapped the IAC a couple of times on the side (think it might have been stuck), might be worth a try.
 

dougelam

Well-known member
Joined
Jul 19, 2011
Messages
453
Location
Michigan
Corvette
2002 Roadster
My 1987 vette ran perfectly until one evening at 7-11 it just stopped. Finally got it home and pulled the distributor cap. Found plastic parts almost shredded, so I cleaned it out and replaced the ignition regulator and other parts inside the distributor. Would not start. And that's when the headaches began.
New distributor, cap and coil. I've replaced the throttle sensor, have new plugs and wired, but to no avail. When I start it cold, it will not idle until the coolant reaches at least 160 degrees. I have to play the throttle to keep it running until it gets to that temp, all the while belching and backfiring. Once it it there, it will idle but the idle speed ranged from 500 to 800 rpms. Once I have the engine up to around 1600 or 1800 rpms, it seems to run smoothly. I've adjusted the timing, set the throttle sensor to the correct voltage, plugged all the wires back in, and still have the problems.
My next step is to replace the IAC. My question is: do my car's symptoms sound like a bad IAC? And second, can the IAC be replaced (removed and a new one installed) without taking the throttle body off? I don't see any way to do it, but thought someone might know a way. Any advice would be appreciated!
Sounds like you have a couple of plug wires crossed

Sent from my SM-N920P using Tapatalk
 

brewster1943

New member
Joined
Nov 7, 2016
Messages
3
Location
Edmond, Oklahoma
Corvette
1987 Blue Convertible
How t get it out?

I'm interested in the IAC replacement too. I had some issues with mine, but it was intermittent. When it happened the car barely ran till it was warmed up.

In my case, when it happened, if I shut it off and let it set a little on restart it was fine. Another was it went away when I took a plastic faced hammer and rapped the IAC a couple of times on the side (think it might have been stuck), might be worth a try.

I will try that. I used to call your suggestion the "sledge hammer adjustment." Of course using a light weight plastic hammer. I have a new IAC, but so car have been unable to get the 22mm, or 1 1/4, socket on it. Too much stuff in the way and it's a really tight fit on my '87. Looks to me like i'm gonna have to remove the throttle body to change out the IAC.

If anyone has a way to replace the IAC without removing the throttle body, please, please share it?

I'll let you know if the sledge hammer adjustment works. Thanks for then ideas.
 

brewster1943

New member
Joined
Nov 7, 2016
Messages
3
Location
Edmond, Oklahoma
Corvette
1987 Blue Convertible
IAC Replacement

Sounds like you have a couple of plug wires crossed

Sent from my SM-N920P using Tapatalk

Nope. Thought of that and checked and rechecked the plug wires. Thanks for the suggestion…. could have been that, but it's not.
 

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