when it starts up cold the engine revs up to about 2800 rpms, then quickly drops to about 500 rpms, then back up, then back down, then back up, then back down... and keeps doing it for about 5 minutes, then it warms up and settles down. but if i give it any gas, it starts to rev up real high again, then comes back down slowly.
it has a lobe at idle like its got a decent cam too. i was told the engine was stock, but it sure doesnt sound like it!
is there somthing that could make it "sound" radical as heck, and make it do that all at the same time?
computer isnt throwing any codes either. weird huh?

otherwise, it runs great. new tranny just put in.

1991, TPI 350, 5 speed. stock computer.

 

Have you tried cleaning the throttle body and IAC? After that, you can set the minimum air and TPS voltage. Usuakky a hunting idle is the result of a dirty/sluggish IAC. To effectively clean it, it should be removed and disassembled. It only takes a VERY little varnish to slow down the IAC operation, as shown in the photos.

DIRTY...



...CLEAN

That's all it took on this particular unit to get is to respond quickly enough to control the idle speed successfully, without the "hunting". Just a little cleaning and one drop of clean oil on the pintle rack gear and it's like a new one.

 

well someone lied to you...350 TPI + 5 speed never existed. Either the car is a 305 TPI or the engine has been swapped. I have my money on it being a 305. A lot of people probably wouldnt know the difference even if they bought it new.

 

Considering he DID say "new tranny just put in"...maybe it was an auto to manual conversion...

 

hopefully its at least a world class t5 or youll be replacing that again very soon. Hell even if it is a world class t5 youll probably send it to the moon if your not careful.

 

not worried about blowing it up. just fixing it. its not mine, its my friends. it DID have an auto, and now it has the T-5.

im going to delve into the IAC motor thingy. its in the throttle body right? boy oh boy.

 

Yeah if it's the manual trannies that were factory on those cars it wouldn't be paired with a 350. A 350 will tear that transmission up. Most likely you've got a 305 in there. 305's a good motor with lots of mod potential. Still it's no 350. But you can change that later.

 

I cleaned the Air valve. IAC. whatever thingy. Its doing the SAME THING. im thinking computer related? its a MAF engine, not MAP.

The cam pulls 8" of vacuum @ 800 Rpms. I touch the throttle and its REALLY sloppy, it hesitates then revvs up really high then comes back down slowly. its very very bad throttle response. and it doesnt even respond right. i give a TEENY gas and it jumps up to 3K. i let off and it sits up there and comes back down slowly.

what the heck is going on?