High idle
 

My 1990's idle is probably 1800. I am guessing a little since the tach doesn't work. I have looked all over for vac leaks but not found any. What else could it be?

Could be? Much!!

If the car is a C68 (ATC) RPM can be retrieved from the AC Control Panel. A C60 car it can't be. Get access to a scanner, hand held tach to get proper RPM I'd think for a start. A guess at 1800? 1800 is very high.

It is an ATC car. I am selling it so trying not to spend the money on a scanner. Is there a way to disagnose without a scanner?

If you have a laptop you can buy the cable for around 50 bucks, the software (tuner pro rt) is a free download.

Without a scanner you'll spend more money swapping parts then you'll spend on the scanner.

Too many inputs in the equation to guess. For example, temp sensor, MAF sensor, O2 sensor, IACV position.

Also could be worn throttle body bushings holding the butterflies open.

Data from the ECM will point to the problem.

Find a facility to do it for you? Throw parts till it works or hopefully someone nearby can lend you one. If I had to buy your car in that state, I'd definitely offer you way less since I have no idea what the problem is. It might be worth it to get a scanner or get it fixed or at least diagnosed.

Finding someone that has a clue working on these cars has been difficult. Supposedly Advance auto will run a scan and get at least some idea as to what is going on. At least that is what I have been told.

It also has a check engine light on it. I have replaced the temp switch, MAF and O2. I checked the IAC and the plunger is moving freely. Does that mean it is good or could it still be bad?

Thanks
Wade

What you need is data that the ECM is seeing. What does it want idle to be? What does it see as coolant temp, oil temp. What IAC count is. Someone could chime in and give you a rough idea what the MAF value should be

If it has a check engine light you can short the terminal to get the code that MAY give you a direction to look at

I found someone with a scan tool. I hope to get it scanned tomorrow afternoon.

Have an infra red thermometer to scan the sensors while you are at it. It's nice to know that the ECM sees the IAT at 95 and the thermometer is pretty close to it on the scan, for example. Also, you will be able to see what the command idle is. If the ECM demands 2000, you need to know what makes it think that. If the ECM sees 0 IAC counts, turn the adjustment screw on the TB out, rev and repeat. If the screw is maxed out, you have an air leaks somewhere. Maybe in the mating surfaces or maybe on the hose. Ask me how I know.