mackdjh

My 85 Iroc I just did a 305-350 TPI swap has an erratic idle and is very hesitant when giving it gas. I have changed the injectors to 22lbs, switched proms and limp mode chips from a 85 corvette 350 TPI (the reason I chose a corvette for the chips is GM only made one 350 TPI in 85, which was the corvette, And the ecm's matched) I changed the esc and knock sensors. When I start it up the idle will shoot to about 1200 and drop idle to around 500, then stall (sometimes this happens a few times) Then the next time I crank it over it may shoot to 1000 maybe but stay idling around 700-400 rpms and start bouncing all over from 1000 to 300, almost stalling, kick back up... over and over again... Plus when I give it gas, the response is horrible. Sometimes the rpms may drop almost to stall or rise a few seconds after pressing the gas. I don’t understand whats going on with it. Some days it loves to run and I can make her scream like a raped pig and others it does like me. Anyone have any ideas? Thanks..

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formula_novice

Check your fuel pressure and make sure it is not fluctuating.

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mackdjh

I checked the fuel pressure, its not flucutating at all. Stays constant when running. I have a ERG failure on the check engine, I dont think that would cause my idling problem and hesitation, do you?

pandin

A dirty EGR valve, stuck open will act like a vacuum leak.

Stuck shut will not be noticeable, only set code after about 10 mins of driving.

Unplug the IAC after turning key on, engine off and see what kind of idle symptom you get. Do this after the first warm up. Idle should be high and steady.

mackdjh

Thanks for the input, I unplugged the IAC and it did idle high and steady for awhile then dropped down to about 500rpm with improved reaction when pressing the gas. Would that mean a bad IAC sensor?

I have pulled the EGR valve and it’s not stuck. I cleaned and put it back as well as tested the solenoid which came out ok. I think I might buy a vacuum tester and test all the lines.

pandin

If the IAC was retracted, the Idle would be high, it was. I am not sure why the idle came down to 500, It should have stayed at the high idle speed as long as the IAC was retracted.

All this means is, that it would unlikely be the IAC, unless the passage way is pluged up. Something lowered the amount of air to the engine to drop the RPM or the fuel got way rich. Check the plugs at idle and smell exhaust for richness.

lunaticinaZ

i forgot to plug one of the vaccum hoses in off the egr solenoid and my car idled like that.

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1973 ford truck is in memory of my old man. He bought it in hopes of fixing it up one day but that day never came. So here's to you dad I hope you like it. 3-20-1954 to 6-3-2006