I bought an 89 GTU 2 weeks ago. When I bought it the idle was a bit rough and lumpy. The idle would fluctulate between about 600 and 900 and when it would drop the car would run rough. Under power, it would run smooth.

I had a mechanic friend look at it. He found that a vacuum hose was totally hanging off. We reattached that and it ran a bit better. He used carb cleaner and found that the gasket between the dynamic chamber and the upper intake manifold was leaking.

This past weekend we replaced that gasket. During the test run the car ran perfect. It idled very smooth at about 750-800 rpm. We took it out on the highway and and I noticed that the car had more top end power. Satisfied, I went back to my friends house and hung out with him for about an hour.

On my way home the erratic idle came back. Pretty much same as earlier. My guess is that its another vacuum leak. Either my friend Chris didn't put a vacuum hose on tightly and it popped off, or that he put them on wrong.

Could someone lend me a hand here. Thanks.

 

Well, then check for vacuum leaks. Also, adjust your TPS and clean your BAC valve. Those are the three most common causes of poor idles.

 

My brother and I just looked at it. We couldn't find any loose or disconnected vac hoses. We definitly think that its not getting enough air in the fuel mixture.

BAC valve? How do I clean that?

 

have you done a tune up on it yet? Check your plugs and air filter.. thats pretty much the first thing you should check whenever your car isnt running right.. Atleast thats how i look at it

 

Simple. take It off, run a single wire to each terminal of the Bac Valve. run them to your battery. You will hear a click off everytime you contact. Give a shoot of WD-40 In there, reapply to Battery to work In the grime than wipe out the grime and redo until you think the Bac Valve Is good. Be sure to blow out all acess before you reinstall to Dynamic Chamber.

 

When doing this procedure, DON'T overheat the BAC valve. If you overheat the coil, it will burn out and then you will need to replace the valve. Only apply 12V for a short time, then wait 5 seconds before you do it again.

 

Any ideas other than the BAC? It seems to be running a bit rich.

 

I just cleaned the BAC. Idle is a tad better and the engine seems smoother. But she is still misfiring and I still suspect a vac leak.

I'm gonna change plugs and also check the AFM. Does anyone have any info on cleaning/checking the AFM?