I just had a 3" pettit downpipe installed, and have noticed that after a highway drive, and shutting down for a few minutes that when i restart the idle is fluxuating between about 1000 and 300 every few seconds, feels as if it will stall if i dont put my foot on gas. After i drive for a minute or so it levels off and seems ok. have only had the downpipe on for a couple of days. Have no other mods to speak of.

any thoughts?

 

run a ground wire from DP to a known good chassis ground. I've heard of a bad such ground causing problems w/o2 sensor. Also could be an o2 sensor itself as it had to be monkeyed with to put it on the new downpipe.

t

 

maybe the extra flow from your new downpipe cause a vacum hose to pop off.

 

Any chance you have a PFC already?

 

The decrease in back pressure affects the idle speed, and the ISC/O2 feedback control tries to keep it where it was before.

The idle control is starting to get outside the normal operating parameters that is was running at and can't quite do it. That is why it is HUNTING. Adjust the air adjusting screw in the TB. Try both opening it or closing it by 1/2 turn increments until best idle is achieved. I would try closing first.

 

Whats the TB??

 

throttle body.

 

thanks a lot chuck you beat me to it! haha

 

Jonathon,

What's happening in Louisiana, keeping Freddie straight?

Maybe because I had learned on Weber carburetor cars and understand them that when I got my RX-7, it was easy to cross over to FI. But with FI, you still have to understand the basic air flow dynamics as associated with carbs.
But my real start was with alky fuel powered model airplanes in grade school.

Must be tough to come out of high school/college with not even bicycle knowledge and try to work on modern cars.