idle speed varies too much
I have a 90 ford TEMPO with 170,000, manual, FWD.
The engine has rough idle. Idle speed varies a lot, from 500 rpm to 1,500 rpm. Sometimes, the engine is dead during idle (rpm is too low). I have to push the gas pedal to keep the engine alive. Whenever the engine idles, the rpm goes up and down, never stays constant.
I had this problem for a long time. It is getting worse recently.
Another problem could be related to it: during cold start, the idle speed goes lower and lower, at last the engine stops. I have to push the gas pedal several times to keep the engine running. When the engine is hot, this problem goes away.
Any idea is highly appreciated. Thank You.