Idle Problem

[jcase350]

I have a 90 Camaro iroc with a 350 TPI. My Idle is pretty rough on it. It will go idle high then low and almost die especially when I put it in gear. Any ideas on what to check first??

[wrightz28]

any trouble codes?

vacuum leaks and IAC operation is where I'd start.

[jcase350]

No trouble codes.

[97cavalier]

how manny miles are on it? got a tune up latly? it sounds like a vaccume leak, or maybe a TPS sensor.

[jcase350]

How can i check to see if it is a TPS problem? I checked for vacuum leaks and didn't find any. Would advancing the timing about 10 degrees cause it to idle rough?

[97cavalier]

ya, that is a little to much, try like 4 not 10

[Morley]

Factroy timing is set to 6* BTDC with the EST wire disconnected and the car in D.
For an unstable idle start with removing the IAC and cleaning it. Also clean the IAC bore and passages in the throttlebody. Next, fully retract the pintle on the IAC (push down firmly on the pintle and rock it back and forth, it will retract.) Reinstall the IAC.
Next check the voltage output on the TPS top 2 wires. With the key on and engine off the voltage should be .54 +/- /.17VDC. While the voltmeter (digital only) is hooked up, open and close the throttle and look at the meter for any dead spots.
After that, a good tune up, plugs, wires, cap & rotor.

[jcase350]

I knew that 6 degrees BTDC was factory, but I wasn't sure if increasing that to ten would make it idle rough. I will try that and let you know what happens. Thanks