'89 Firebird Formula, 305 TBI, auto. VATS has been properly disposed of, underhood is still all factory original.

It starts, idles and runs perfect until a short bit after the fan kicks in....then it won't idle, or sporadically idles correctly. Still runs down the road just fine...engine only quits quits when I stop the car. If I shut the engine off and wait a few minutes, it idles fine....for a few minutes. Then it starts all over again.

Anyone got an idea? TPS, perhaps? The car has sat idle for about 4 years with only an occassional start-up. Could corrossion on some actuator or sensor be a contributing factor?

Just need to know where to start looking.

Thanks

NM

 

I would start by checking all your vacuum lines and connections. Then go from there. Might alsp chech your distributor spark module.

Stee

 

Sounds to me like closed loop, for whatever reason, is causing this idle problem. May want to replace the O2 sensor.

 

well i am not a mechanic but i had a similar problem not so long ago, somebody told me it was just tuning! my cousin put it on a scaner and he said it just needed to be tuned and it worked! before that though, i had changed the spark plugs and wires, cleaned the injectors, cleaned the iac valve (idle air control), changed the belt, etc...and nothing worked, but try the iac, those things get really dirty, just clean it with some throttle body cleaner, but be careful with the little seal that it has, it's pretty fragile, if you want to buy the iac valve, it runs about $45 bucks, it's kind of expensive for a little thing like that, but according to most poeple here it's very important and may be the answer to all your problems. look up my threads somebody gave me a link and it tells you everything about the iac how to...etc, good luck!~jorge

 

How does the engine run if you keep it below 230 deg's? In other words if you keep the temp low enough to keep the fan from coming on. There is a posibility of a short in the fan or fan relay or the fan may be drawing too many amps. If you don't get the correct voltage to the ecm or dist the car will run bad.

Steve

 

Ok, how about the egr coming on at idle after warm up? I see this once in a while. The egr solinoid does not close all the way and allows egr flow at idle. And along this same line - try pulling up on the egr with your fingers once the engine is warm and having the problem. Does it move freely?
Just an idea. I see egr problem way to often.

Marcello

 

O2 sensor and filter are new. Don't know about the spark module.

Vacuum lines seem to be in good shape(I would think that would show up even when cold).

Sorry...I know I should, but I don't know what an IAC valve is.

I hadn't thought about a low voltage problem before.....possible, as the guage shows me charging at just under 13 volts.

I'll check the EGR. Seems odd it would cause an almost "no fuel" feel to the throttle....but worth a check.

Whatever it is, I have about a week to correct it. Title should be in in about a week, and 18 year old daughter is going to have it as her only transportation.

I can fix it now...or on the side of the road late at night!

Thanks for the suggestions and ideas!

NM

 

OK....I think I may have a voltage prob.

Guage shows just under 13 at cold idle....drops dramatcally when the fan kicks in.

For real fun, with the headlights and heater fan running, it almost hits the "red zone".

With that kind of voltage drop, I can only imagine what the 'puter and the pump are doing.....and none of it good!

Battery or alternator? Its' one or the other, and I can't remember which causes this prob.

I'm bettin' alt.

Thanks

NM

 

wouldnt the condition of the belt affect your alt.?

 

You know, I hadn't thought about that.

I'll check that tomorrow. It probably wouldn't hurt to replace it, anyway.

The car HAS sat idle for about 4 years!

NM