QuestionI have a 91 Mitsubishi Eclipse, 1.8 L, automatic, non-turbo. I have been having some problems with rough idling and it also tends to shut off when coming to a stop. Sometimes while driving the RPM's will drop to zero and I will have to pump the gas pedal several times to receive full power back. I have been to several mechanics and have replaced the O2 sensor, idle speed control, and have had the ECM sent out for diagnostic purposes to be rebuilt, but they said the computer is fine and replaced the known faulty components for me. Also, once while driving the engine would not shift out of second gear...the RPM's were at the 4 mark and the car would not go faster then 35mph. (this only happened once)I was wondering if you had any other suggestions as to what should be looked at next. The engine light is working and has never lit up. Thanks for any information/guidance you can provide.
Pamela Stott
AnswerPamela,
You should have your timing checked, along with timing belt. If your timing belt is not set correctly, your engine will idle rough and stall at times. Also get a compression check done as well. A quick fix could simply be to replace your PCV valve. A little valve that releases excess crankcase pressure. Very inexpensive and easy to replace.
There is a component located just below your throttle body called you Fast Idle Air Valve (FIAV). It's purpose is to provide additional air when the engine is cold to increase the idle speed and therefore warm up the engine faster. The FIAV is the reason (the only reason) that coolant flows through the throttle body. If your rough idle/stalling problem typically happens after you engine has warmed up, you may want to have your FIAV checked out.
Other areas to check are your fuel and ignition systems. Have your fuel pump checked and your fuel filter replaced. A clogged fuel filter will reduce the amount of fuel entering your engine and cause poor idling and possible stalling. Your ignition system is basically made up of your alternator, distributor, spark plugs and spark plug wires. You'll want those items inspected and replaced if necessary. You spark plugs and plug wires should regularly be replaced every 30,000 miles or so.
The last thing I can think of to have checked is your transmission. Your torque converter kind of acts like a clutch in a manual transmission vehicle. If your torque converter is not changing the torque requirements when your car is stopped, then your RPMs will quickly drop down to 0, and the car will stall. Next time you're at a light or stop sign, and you feel you're going to stall, move your shifter to N (neutral) and see if that brings the life back into your car. If it does, have your mechanic focus on our transmission and your ignition timing. Also have your transmission fluid checked and replaced if low or dirty. It should be flushed and replaced ever 30k-40k miles.
As you can see, diagnosing a rough idle and stalling problem is not easy. There can be several causes, and every mechanic and person with some knowledge of cars (like me) might have different views on areas to check. Next mechanic you bring your car to, give them the list of items I've recommended to have checked, and then you'll know what worked or what can be ruled out.
Good luck!
