305 TPI problems

Quinton Morse
35

Asked by Quinton Aug 08, 2010 at 08:54 PM about the 1985 Chevrolet C/K 20

Question type: Maintenance & Repair

I've got a 1985 Chevy K20 pickup with a 305ci TPI engine from a 1986 IROC-Z Camaro. A while back my truck began idleing high and lost power. I thought this was a vacume leak because it had most of the problems that a vacume leak would cause and when the truck was running and you looked under the hood it sounded like there was a leak coming from the Idle Air Control Motor. Finally I decided to get it fixed and bring it to my friend's garage. He told me there was no vacume leak and replaced the IAC motor just to be sure, still had a high idle and loss of power. He also checked the timing only to find that it was ok. I started the truck to bring it home and the RPMs raised and lowed sparaticly and kept trying to stall until about 5 minutes later when it warmed up, where the RPM stayed at about 1200. I drove home and everything seemed fine. After letting the truck sit for about 2 hours I went out again and noticed the engine making a slight sputtering/popping noise when I gave it gas, my friend thought it could be a bad Spark Module but i'm not sure.
Has anyone had any problems like this with their Camaro/Firebirds or does anyone have any sugestions?
Thanks for reading

1 Answer

Michael Stewart
315

I worked on a Camaro once that would not idle because the mechanical advance springs fell off and would cause the initial timing set piont to change while idleing. This would then cause the idle speed to increase. If you turned the motor off and restart it, the idel was fine until you gave it some gas and then the idle would go up and down or stay high. Have your friend check the timing at idle and then increase the rpms to see if the timing goes up like it should. It should return to the same timing while the rpms decrease. Does it have HEI ignition? They are not good and wear out causing lots of problems.

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