A questions a friend asked me to find out about...It has to do with idling of the car

[MaraSport]

A friend of mine with a 98 Firebird with a flowmaster exhaust and Quad tips... Asked me to ask yal, why does her car idle like it suppose to and then all of a sudden revs up about 4 or 6 hundred rpms and then idles back down? It only does it every now and then... and that day the car had been running in place for about 2 or 3 minutes and then it kept doing it every few minutes until we departed company...

What's wrong, any help will be appreciated... Thanks yal...

Later...
Mara...

[Performin Norman]

I'm no expert here but I'll throw some comments out. Maybe Fred or someone like him will chime in and probably correct me.

It can be many things.

1. IAC-Idle Air Control valve

2. Vacuum leak

3. Sensor going bad. ie. O2 sensor etc.

Have you had it put on a scanner yet? I'd check into that.

[RangerBob]

Alternator kicking in and out

[MaraSport]

She had took it to the shop and they had said that whatever it is they didn't know what was wrong... I talk to somebody that works at a dealership and they said it is either normal or he would take it to the dealership and see what was wrong... BUT DARN THE DEALERSHIP COST SO MUCH...

And too, if it was normal then wouldn't mine do it...

[Christopherrr]

reminds me of firebird that had a same problem...is the 98 3.8 controlled by a electric throttle? I know the 99+ does...a bad connector was the source of the over revving (sudden rev then back down to idle). Can't remember what the electric motor make was...imported I know, think it was Hitachi. Give that a shot...clean the connectors if it has electric throttle control.

[MaraSport]

Thanks...

Thanks...

Thanks for all your help and especially yours, LimTeng99TransAm...

Later...
Mara...

PS= I thought that the problems was in the throttle body and everyone sweared out of the dickens that it wasn't the throttle body but the computer... Thanks again...