For me it was the computer (ECU, also called ECM). I had replaced the Mass Air Flow (MAF) Sensor (aka Airflow Meter) first, which cost almost 2x the money of getting the ECU repaired (avproecm.com did it w/lifetime warrantee). A temporary work-around for me was to unplug the MAF sensor (right after the air cleaner). If you're lucky, the MAF sensor might only be dirty and you can buy MAF sensor cleaner to try fixing it. Note there are 2 bolts to take out as well as the hose clamps to remove, but it's not hard.
Apparently one common way the ECU can fail due to leaky electrolytic capacitors somehow changes the MAF sensor reading or makes it invalid. If voltage on the middle pin (I think it was) rises and falls with engine RPM and if the voltage range matches the table in Chilton's on the subject, then I'd assume your MAF sensor is good. I opted to change it, but later regretted not trusting the test results. The new one didn't change a thing. When I got the ECU back and put it in, the truck started right up, to my delight!
If you have't unplugged the battery for an extended period of time - don't until you're ready to let it sit for awhile. Following the test in Chilton's manual for one of the MAF sensor pins, I unplugged the battery for 5 minutes to clear ECU memory. Without it's memory of settings learned before my problem started the engine ran much rougher and was very difficult to start. I could do it by pumping the gas pedal, but it was very abnormal. I changed my O2 sensor also before the ECU repair. But later I found the reading from the O2 sensor doesn't get used until the engine warms up, so if you're having problems before temp needle starts rising, you can rule out the O2 sensor as the only problem.
Maybe your problem is significantly different than mine, but I've answered assuming it's the same. Sounds similar. Good luck!
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05-23-2011, 03:06 PM
