1995 chevy cavalier manual transmission. rpm's increase to over 4000 when the clutch is pushed in. It is idling high at around 2000 any other time. Now the check engine light is on and it is pulsating between 1500 and 2000 rpms, it just goes up and down up and down, just sitting at a stop in neutral.

You cannot adjust the idle speed. The issue is either a bad ildle air speed control or the fuel pressure regulator on the fuel injection rail.

I guess that you have a manual transmission. If that is the case you have a clutch on the way out. Slow slippage that gets worse as the plate gets hotter. If an automatic it is possible that the overdrive is not holding due to low pressure in the box. Have a pressure test done on the box--- have the fault codes read. From experience 120 kph is around 3200rpm for most cars and the 800 rpm difference indicates that the o/dive is not working as it should.

I would start with ect. That is the engine coolant temperature (sensor). That sensor monitors the coolant temp and tells the computer to increase engine RPM so the engine warms up faster. In the mornings when you first start your car and it idols high, that sensor is sending that information. If you have a code for this sensor start there.

The most common cause of high idle is an intake air leak. It will cause a lean condition to the O2 sensors and the PCM's solution is to increase the fuel mix resulting in faster idle. It can also cause a Check Engine Light if the idle remains too high for too long. Do a smoke test or soapy water test around the intake manifold and throttle body. If you detect any leaks, seal them and try again.

It sounds like your clutch is slipping. It's an early warning sign that clutch is going to need to replaced soon.

Your idea of a clutch problem is correct. you will need to replace the clutch,pressure plate, throw out bearing and have the flywheel turned or replaced on car. Sorry to tell you this but it will have to be done to correct your problem. shop around to find a good quality clutch repair kit with all the parts that you will need. and remember in shopping that all companys have different warrantys on there products. hope this will help you.

There could be two problems i can think of here. First would be a computer problem. The computer might be telling the car to run at a high speed. A problem like this might be fixable from your local garage. A problem like this could be expensive. Second, as engines age, they natually tend to idle higher. This is a normal occurance. This is accompanied by a decrease of gas mileage. For me, i went from normal 26mpg down to around 22mpg. A problem like this can be fixed by using fuel additives aimed at high mileage cars. I have used fuel injector cleaners, and that has brought my car back to her glorydays of 1996. I hope this helps, if not let me know.

You could have a bad valvebody in your transmission or a bad pump in your transmission or your clutches are bad. In any case you have a bad transmission. Please rate my answer.

check all your plugs and wires

sounds like a bad a/c compressor and you car thinks the all the time.