tedasaurus

I have a '93 GT Conv with 36k miles and 5spd. Previous owner placed a BBK induction, MAF, headers, and an offroad exhaust and flows. After EVERY start the car idles rough, hesitates, and stumbles for about three miles, then clears up everytime and runs normal. Any advice that would fix this?

tedasaurus

Oh yea, the '93 5.0 also has underdrive pullies and an electric fan on it. If I had to guess I would say the most likely culprit is the BBK MAF. Next I would say the headers and off road.

WhiteFoxGT

Let the car warm up before you start driving it? The computer is probably on closed loop (or is it open? I always get them confused) That means it changes the fuel and timing curve to help the car get warmed up.

musclemustang94

If it is doing it EVERY start up then you might have a bad Engine coolant temperature sensor.

tedasaurus

Yea it does it on every start. Wouldn't a bad engine coolant temp set off the check engine light?

mattdel

not necessarily. only if it was way way out of range. i'd also get new o2's. 35k on a 13 year old car, they can't be in too good of shape rust wise.

mustnglvr

Dont rule out the wires going to the connector for the sensor those are a problem on older cars.

93 LX FiveO

sounds like a mix of problems..

- poor TPS voltage
- dirty IAC
- bad MAF sensor

maybe even too thick of oil? 36k miles should be running some thin oil

Blckstng93

Im going with the ECT. It effects the air/fuel, spark timing, and idle rpm at startup. The computer switches to a fixed warm signal when they go bad so when the engine does warm up it runs properly but during a cold start itll give you grief. Needless to say that once everything warms up the engine will run fine. A low coolant level will cause a false rich rich signal leading to a warm stumble.

It never hurts to check you TPS. It should read betwwen .98-.99v key on engine off. youll need a voltmeter and 2 pins. I believe its a green and black wire? At last check mine read a pathetic .58 but never had any troubles with a cold start.

As for the MAF, im not sure. I had one go bad causing a stall but was only during reverse and it didnt matter what the temp was.

Your o2 sensors should be replaced every 30k miles so if you havent already, replace them. Clear the computer when youre done.

Stanpower

http://www.aa1car.com/library/2003/us80312.htm