Well I've been chasing this one for a few months. My revs don't drop any longer when the oil cap is removed. I have cruddy idle when hot and cold, it now floats between 400 and 600 rpm. I've tried adjusting the idle air bypass with the diagnostic pins shorted. I've replaced the O2 sensor, mostly because I didn't know how old it was and I have 130k. It didn't make any difference. I've replaced the idle speed control valve, the new one actually buzzes and the old one was shot. still no difference. is it possible that my oil tank vacuum restrictor is clogged? Haven't over filled it, and there used to be a difference when removing the cap when it used to idle at 850. I've inspected the vacuum hoses to the intake and sprayed carb cleaner around, but haven't found a leak... so, should I go for a head temp sensor next or is there something less involved that I should try first???

Thanks!

 

I would try the head temp sensor if you've tried all that stuff. Im in the process of a complete rebuild of my 84 and i found so...so many potential air leaks, the boot between the intake halves, loose manifold nuts, rubber hoses on the siphon jet on the left side behind the blower fan, vacumm lines. really bad. but Im replacing everything so I dont have any problems down the line.

 

I had a similar problem. It was the mixture. Take it to your mechanic and have the mixture checked. Mine was off, and once adjusted the car has been perfect. Sometimes the simplest solutions are the best.

 

Thanks for the suggestions. I don't have a mechanic; not sure that there's anyone up here that can do a mixture adjustment... Since I'm at 6800-8500 feet most of the time, it's something that I think needs to be done up here. The county used to have emissions testing last year, so I was thinking I'd try to convince the quicklube that has a tester to let me use their gear and adjust it in their bay. Or, would it be close enough to drive it down to Denver at 5280ft were there are some good shops? The thing that's odd is that it was fine for the first 3 years I've owned it and the car has lived here for 10. Could a clogged catalytic cause this?

 

mixture goes out as the gas gums up injectors and there's more carbon to soak up the gas (even worse on a cold start as carbon acts like a sponge so get an actual intake flush via a vacuum port and not the pour in tank stuff), im not sure what motoronic is as they aren't fooled with as much but SC's (which I set all the time) run at 2.5% CO +/- .5% ypu need a 4 gas analyzer to do this.

 

I think I got it... took the air flow meter apart & cleaned the potentiometer with alcohol. bent the wiper a bit so it would make new tracks just slightly below the old ones, and diddled with it until I got a smooth resistance transition. now it's idling at ~850. COOL!