I have a 2002 Tacoma 2wd reg cab with a 2.4L 4cyl. One day while driving I came to a stop when all of the sudden the engine stumbled then stalled on me. When I tried to start it again it would just run for a second then stall. I had to keep my foot on the gas to keep it from stalling again. After I got the truck home I began to investigate what went wrong. The check engine light never came on.
When I can get the truck to idle the engine runs really rough and I can see black smoke coming out of the exhaust telling me its running very rich. I changed the sparkplugs and checked the compression of the engine and its within spec. I also changed out the coils packs that connects to each spark plug. At this point I assumed it was the MAF sensor so I replaced it but the problem still remains. I also replaced the air/fuel & rear oxygen sensors but that didn't seem to help.
I hooked up an OBD2 scan tool to monitor the various sensors while the truck is idling and noticed the ecu is retarding timing which I'm assuming is causing the engine to run rich & rough idle. The check engine light never came on so I don't know why the ECU is pulling back timing.I notice when I unplug the MAF sensor the truck runs normal. I'm guessing the ECU is running in "limp mode" at this point but when I reconnect the MAF sensor the problem comes back. Eveything is telling me the problem lies with the MAF sensor but I've replaced it with a brand new one. I even tested out the old MAF sensor on a friends Tacoma and it runs fine.
Does anybody have any ideas to what the problem could be? I'm at a loss................