Engine Mechanical problem
1988 Pontiac Sunbird 4 cyl Front Wheel Drive Manual 206000 miles
At start-up (in neutral) the engine will idle fast, then slow, then fast, then slow, then die. Sometimes it will start up fine, then the very next time the above problem will happen. This has been happening more and more often. Now it will seldom start properly at all (though it will ALWAYS start, and idle fast and slow for a few seconds and then die). There are no error codes.
I've had 2 mechanics work on it. One fixed some vacuum leaks and cleaned a bunch or oil out of the distributor, the other found the fuel pump was failing intermittently. Both problems have been fixed (fuel pump, fuel pump strainer, and fuel filter replaced, vacuum hoses replaced, distributor cleaned), but the problem keeps returning with no changes. And it's getting worse.
I've replaced the distributor cap and rotor, tested the ignition control module twice at Auto Zone (no problems found with it) and replaced the coolant temp sensor. The battery is brand new. The MAP sensor and O2 sensors are also new.
During start-up, while the engine is idling fast and then slow the headlights (if testing at night) will get brighter and then dimmer dramatically (I figure that is just because the change in idle speed). Then after a few moments the engine will just die. Pressing the accelerator down has absolutely no effect on the problem, but will cause the engine to race (if I press it at the moment the idle is fast). But the engine will still die every time this problem happens--regardless of what I do. After 5 to 30 times starting up the engine, it will sometimes start up and idle just fine.
Once it does start up fine, it will continue to run fine until stopped, then it's a gamble whether it will start up again or not--usually not, at this point. Though if it has been running a while and is nice and hot, it seems to be more likely that it will start up again and idle fine, if started immediately and not allowed to cool down.
I've checked the IAC for carbon build-up and cleaned a small amount of carbon off of it, but no change. Though I have not yet checked to see if the IAC plunger moves like it should.
Note: Just before this problem started happening the very first time, I had drove up a very long and steep hill for about 20 minutes and noticed the engine losing power and overheating by the time I reached the top. There was also a smell of burning oil. I have no idea if that's connected.
Tuesday, October 20th, 2009 AT 6:23 PM