CIS car not running right...

VaSteve · 09-02-2009, 07:23 PM

My SC which used to run great has developed a problem. It used to start right up, rev up a bit when cold and drop to a nice idle at 950. Lately, it drops down to around 500 at idle. Otherwise, it seemed to run and drive OK.

Last weekend, it really went bad and it would barely idle. I looked it over and found that one of the injectors backed out of the manifold. Because of this I suspected that all along that I must have had a vacuum leak I ordered some new parts and put the injector in this evening.

I started it up and the car still isn't right. It stumbled a bit at start up (I suspect from me fixing it). I took it for a short drive and the idle never went back to the proper 950 range. I was hopeful that this was related to the injector backing out. Basically, the car operated as it did before this past weekend.

It's been years since I messed with the air fuel mix or the idle screw. I don't want to start turning screws and make it worse.

I have a set of old CIS test gauges that I got from someone, but I have never used them, so I'm a little wary of squirting gas all over the top of the engine.

Anyone have a guess as to what might be the cause? I won't have any significant time to mess with it until the weekend, but the suspense is killing me.

Won · 09-02-2009, 07:45 PM

Do you mean the car was running well when it had the vacuum leak? If so the mixture that was set to compensate for the leak must be off now that the leak is fixed.

You can easily check the mixture by taking off the air filter cover and pushing/pulling on the meter arm to see whether it is currently too lean or rich. Disconnect the O2 sensor first.

VaSteve · 09-03-2009, 03:03 AM

It was running ok and started with the ~500 rpm idle a few month ago. But it was somewhat intermittent. Last weekend it would barely run. I found that the injector had popped out. I fixed that but its still idling around ~500. I haven't tweaked the mix in a long time and it has run ok since then (up until a few month ago).

Maybe I had two vacuum leaks but only fixed the most obvious one. If that's not it, any guesses?

Flat6pac · 09-03-2009, 03:23 AM

Get some carb cleaner and spray it around your hoses and intakes and see if your idle changes. You ll be filling leaks for a second and the idle will change if you have a leak in the area.
Bruce

T77911S · 09-03-2009, 04:03 AM

you have a long list of places to look for air leaks. dont forget the plumbing at the back of the motor, you know, the fun stuff you cant get to. replace the gasket on the oil cap and check the vent hose on the tank.

if all that is good you may want to check and see if the frequency valve is making a clicking sound, check control pressures. make sure the O2 sensor is working.

moving the air plate as said above an easy way to check if mixture is off. then its just a matter of figuring out what is making it bad.

1982911SCTarga · 09-03-2009, 07:59 AM

Without using a CIS gauge set as part of a baseline assessment, you're really just guessing at things.

Correctly hooked up, the gauge doesn't leak fuel at all (except for around the bleed valve in my case -- see my other CIS post and darn you, J.C. Whitney!).

Brian

Gunter · Gunter's Garage

Quote:

Originally Posted by VaSteve

It was running ok and started with the ~500 rpm idle a few month ago. But it was somewhat intermittent. Last weekend it would barely run. I found that the injector had popped out. I fixed that but its still idling around ~500. I haven't tweaked the mix in a long time and it has run ok since then (up until a few month ago).

Maybe I had two vacuum leaks but only fixed the most obvious one. If that's not it, any guesses?

When an injector pops out, it's time to check the O-rings and sleeves on all of them.
If the sleeves and O-rings are shot, it screws up the mixture.
The sleeves are staked and you'll need to remove the stakes before you can pull out the sleeves.
Replace the parts and then set the mixture and idle, it's not hard to do.