1987 TBI - 383 Swap - Runaway Idle Help - The 1947 - Present Chevrolet & GMC Truck Message Board Network

jaxwithanx · 08-07-2012, 11:10 PM

Have a ridiculous issue. My grandfather threw a rod in his 1987 TBI 305. He said one day he was going down the road and the RPM's kept creeping up until he had to stay mashed on the brake to keep the truck from taking off. Finally threw a rod before he could get it calmed down. I had a 383 built utilizing a 454 TB. New chip, exhaust, transmission....everything.

Well I have the new engine installed and it runs great but shortly after it starts the RPM's start to creep up and my mechanic and I cannot track it down for anything. We threw another computer in, nothing. IAC is staying wide open, it seems some sensor has the ECM telling it to keep feeding.

No throttle body gasket leak....about all else we can think of is pulling the distributor (I had already replaced the cap and rotor) and trying a different one.

The truck is running like a bat of out hell but we can't get the idle to stay down at all!!

Any help appreciated.

EDIT: The reason I mentioned the portion at the beginning is it sounds similar to what is happening now. Unfortunately I wasn't around when the engine threw the rod and can't be for sure on the specifics of that story to know for sure if it matches what is going on now. Although it seems more than coincidental. My grandfather is still alive but was diagnosed with cancer almost right after that event happened and while he is still alive - he can't remember much of the specifics of the whole event (it was over year ago and he is already on borrowed time after all the chemo and drugs).

f.monroe · 08-07-2012, 11:20 PM

Could be getting air from somewhere other than the tbi gasket. Maybe a leak within th brake booster?
Just a thought.
Frank
Posted via Mobile Device

jaxwithanx · 08-07-2012, 11:29 PM

Quote:

Originally Posted by f.monroe

Could be getting air from somewhere other than the tbi gasket. Maybe a leak within th brake booster?
Just a thought.
Frank
Posted via Mobile Device

Thanks. Will go check here shortly....any other suggestions are welcome. It's killing me. It idles fine for a bit...then slowly starts taking off....

08-07-2012, 11:10 PM	#1
jaxwithanx Registered User Join Date: May 2011 Location: Houston, TX Posts: 13	1987 TBI - 383 Swap - Runaway Idle Help Have a ridiculous issue. My grandfather threw a rod in his 1987 TBI 305. He said one day he was going down the road and the RPM's kept creeping up until he had to stay mashed on the brake to keep the truck from taking off. Finally threw a rod before he could get it calmed down. I had a 383 built utilizing a 454 TB. New chip, exhaust, transmission....everything. Well I have the new engine installed and it runs great but shortly after it starts the RPM's start to creep up and my mechanic and I cannot track it down for anything. We threw another computer in, nothing. IAC is staying wide open, it seems some sensor has the ECM telling it to keep feeding. No throttle body gasket leak....about all else we can think of is pulling the distributor (I had already replaced the cap and rotor) and trying a different one. The truck is running like a bat of out hell but we can't get the idle to stay down at all!! Any help appreciated. EDIT: The reason I mentioned the portion at the beginning is it sounds similar to what is happening now. Unfortunately I wasn't around when the engine threw the rod and can't be for sure on the specifics of that story to know for sure if it matches what is going on now. Although it seems more than coincidental. My grandfather is still alive but was diagnosed with cancer almost right after that event happened and while he is still alive - he can't remember much of the specifics of the whole event (it was over year ago and he is already on borrowed time after all the chemo and drugs).

08-07-2012, 11:20 PM	#2
f.monroe Senior Member Join Date: May 2004 Location: Caldwell,Tx. Posts: 3,648	Re: 1987 TBI - 383 Swap - Runaway Idle Help Could be getting air from somewhere other than the tbi gasket. Maybe a leak within th brake booster? Just a thought. Frank Posted via Mobile Device __________________ Born and proudly residing in a Red State !



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