2001 Starting issues

[DeanO33]

Hi all,
Long time reader, first time poster. In the past i have usually been able to find my problem by searching but I'm coming up blank. Sorry if this is a repeat. Here is the issue. My mother-in-law drove my 4runner to the store and it stalled in the middle of the parking lot. I got the call and drove out to see if i could start it. I had no luck there. So I towed it home. That night while trying some things I confirmed the fuel pump was turning on. (I did a new fuel pump, filter and timing belt service in October) Plugs are new as of March. Last night i decided to tinker a little more after having a fresh mind. It would start momentarily, maybe for 2 seconds, but run extremely rough and stall. I checked the airbag and air filter, dirty but not clogged. I then unplugged the MAF and it idles fine, but will not rev at all. Actually stalls if you open the butterfly. No scan tool at the local parts store, bought a new MAF and air filter anyways, but the problem is exactly the same. I unplug the MAF, it starts and idles. As soon as i plug the connector in, the engine dies. Sorry for the length, but i want to have as much info to start with. Thanks again everyone, and if there is a thread about this issue, please point me in that direction

 

[Buckaroo]

Do you have a CEL? Likely when you unplug the MAF, the ECM is substituting a value for the air flow so the car idles ok which I think indicates air/fuel mixture. Check to make sure your clamps are tight and you don't have any holes in the air intake between the MAF and throttle body. After that, given you already replaced the MAF, I would look at fuel pressure.

Buckaroo

 

[DeanO33]

There was a CEL before this all happened. I guess I'll start checking for fuel at the filter and see what I have there. I seem to remember the fuel pump only ran when cranking the engine.

 

[DeanO33]

Didn't get to the fuel system yet. Storms rolling in. I took off the intake tube, cleaned it and inspected it. No signs of holes or leaks. Reinstalled and ensured everything else was attached. All connectors and lines seemed attached and serviceable. I did however find that the rear O2 sensor was a little jerry rigged from previous owner. it had what looked like a diode and resistor spliced in on the blue and white wires. so, even though this may not be a problem, I am replacing it. No room for half a$$ work on my wifes DD.