Hey guys,

I recently bought a 92 Formula with a 305 TPI, automatic, about 50,000 miles. The only mods that I know of are a performance chip and matching Hypertech thermostat that makes the engine run cooler (about 160 to 170 degrees).
The problem is that the engine idles kinda rough, even surging between 200 and 300 RPMs when sitting in neutral or park. Otherwise it runs great at all of the driving speeds.
I was told that the rougher idle was just a side effect of the performance chip. Is that the case, and should I just live with it or try and adjust it?
Oh, the air filter and fuel filter are new, plugs are good and the fuel injectors were just cleaned.

By the way, anyone have an opinion on whether or not fuel injector cleaner in the tank does any good?

Thanks!

 

Jeff,

Most often, fuel injector cleaners that are added to fuel are only good as a preventive measure. In some instnces, they can actually help clean injectors that may be clogging. They might be worth trying if you suspect injector problems, but don't expect miracles. Clogged injectors generally stay clogged until they are removed and cleaned.

As for the idle problems, has the IAC been removed and cleaned?

 

I have the same problem, what is iac?

 

IAC is the Idle Air Control, its a valve on your throttle body that tells the computer how much air is passing through the throttle body, and the computer makes adjustments based on the reading the IAC gives. Sometimes it gets clogged, and you have to clean it to make it function properly.

 

What do you clean it with, is the part expensive?

 

It shouldn't be idleing at 200 or 300 rpm (if i understood you correctly) it should be around 500-750 rpm idle speed in P or N. Is there an idle speed adjustment on the TPI engines, like there is with the Q-jet engines? If there is, raise it to 500 rpm or so.

 

Do a search. There are instructions somewhere on how to clean the IAC and how to properly adjucts the idle.

If you can't find anything, I found this info on another site:

http://www.iroczone.com/techartidle.html

http://www.iroczone.com/techartcleaniac.html