sc idle???

[jrrotor]

i bough a 1980 sc widebody beautyfull car ,my question is when car turns on the idle go up and down like in other cars tpi sensor sounds like, dont know where to look any sugestions info will be gladly apreciated. thanks.

[Dave Colangelo]

When I start my car and it has not been run for like 12 hours my idle goes up to about 1800 rpm for a very brief time then settles back to 900 and holds.

[jrrotor]

Originally Posted by Dave Colangelo

When I start my car and it has not been run for like 12 hours my idle goes up to about 1800 rpm for a very brief time then settles back to 900 and holds.

maybe it wasnt warm enough thanks

[Alan Lindquist]

Originally Posted by jrrotor

i bough a 1980 sc widebody beautyfull car ,my question is when car turns on the idle go up and down like in other cars tpi sensor sounds like, dont know where to look any sugestions info will be gladly apreciated. thanks.

Pretty common problem. Search the forum for threads on the WUR (Warm Up Regulator).

Your car has CIS (Continuous Injection System) fuel injection which was common to many cars in the late seventies and early eighties. It's a good system, but it needs to have a balanced environment with correct fuel pressure and no vacuum leaks.

Your car is at the age where vacuum leaks can show up via aged lines and fittings. But the most common problem is a malfunctioning control pressure regulator (WUR). They aren't cheap - a rebuilt unit is about $700. You can get it rebuilt for about half that if you can pull it, wait, and re-install it.

But don't guess at the problem. If you are handy there are a series of troubleshooting steps you can take. You'll need a fuel pressure gauge kit to measure your fuel pressure.

Other causes could be related to the fuel pump and fuel filter not allowing enough pressure, and that is potentially less expensive.

If you aren't handy, find a mechanic you trust to diagnose it.

This forum is kind and helpful if you can take pictures, get the right tools, read previous posts, download tech articles, and stumble your way to success with some experienced guidance.

Search the posts and do some reading. Even if you don't repair it yourself you'll understand it a bit better.

[Dave Colangelo]

+1 for checking for vacuum leaks. The quickest and simplest way to do so, is to start the car and let if warm up to a nice idle. Then remove the oil filler cap. The idle should drop noticeably if it does not you have a vacuum leak. Basically removing the cap simulates a leak which causes the change.

[kodioneill]

incorrect fuel pressure
decel valve stuck
auxiliary air valve stuck
vacuum leak
advance stuck
timing wrong
o2 sensor bad
fuel mixture setting wrong

[Paulporsche]

Sounds like you're mixture is too rich. There can be several reasons for this, including it merely being set incorrectly, or your cold control pressure is too low, among others.

The first thing to do is to get a CIS fuel pressure gauge and measure your control pressure throughout the start/run phase of operation.

If you search "WUR", which is the warmup regulator (the thing that controls the control pressure) and "control pressure" you will find more than you ever thought possible on this.

Once you get the pressures you can check them against the spec for your car.

You should also check, or have checked, your CO%.

Your O2 sensor or sensor relay could be bad. Does your interior dome light work? If not, it could be a bad relay.

As others have stated, making sure there are no vacuum leaks is extremely important. Often people try to make up for a leak and subsequent lean mixture by richening the mix.

When staring from cold, the idle should be slightly high, as Dave states above and, depending on ambient temp, stay that way for a while as the engine warms up.