kwikrnu

The tacoma runs great at idle and high speed and low speed, but it stumbles hesitates or misses at WOT or near WOT at any rpm or speed. The engine trouble light is not lit and no codes are stored I have an autotap scan tool. The engine has 214K miles.
I changed the plugs, used sea foam through the intake, fuel injector cleaner, cleaned the TB, new fuel filter and brushed off K&N filter.
I removed what appeared to be the original factory cat and it was solid - no rattling and did not appear to be clogged or melted. I could see light through it fairly easy.
I checked the resistance of the plug wires and they were between 16 and 19 K ohms specs say less than 25 K ohms is okay.
I checked the primary coil resistance and it was 1.1 ohms cold (about 75 degrees) which is a little high should be .67 to 1.05 from 14-122 degrees...
Secondary resistance was within specs at 13.1 to 13.5 K ohms cold (about 75 degrees) cold should test 9.3 to 16 K ohms.
Checked the MAF mass air flow meter resistance between E2 and THA. That was 1.9 K ohms within spec from what I could tell.
I tried to check the voltage between E3 (brown/white wire) and VG (gray/red wire) with the wire harness connected and blow through the meter but the voltage did not fluctuate as it was supposed to. I am not 100% sure I tested the correct wire but the FSM illustration is not that great...I also used some electronics cleaner on the MAF after I tested it and while the MAF appeared to be cleaner it did not test any differently.

I guess I am down to making sure I am testing the correct wires on the MAF. So if anyone has a picture of which wires I need to test or the color. But I am not quite convinved the maf is bad because the truck runs good at everything but WOT and I think it would probably not run that great if the meter wasn't reading any voltage.
Or, testing the coils when hot. They were somewhat out of range for the primary resistance which might affect all cylinders but at around $100 each they are expensive option to replace and not be the problem.
Or, something else like fuel pressure which could be a lot of different things like the fuel pump or fuel pump control circuit or something.
Maybe I'll do a compression or leak down test on her tomorrow as well.



Any ideas would be helpful.

wvorih

I had a similar problem on my truck and it was the MAF. I replaced it and all was good. Then I looked at the old one and noticed that it was a bit grungy inside. So I cleaned it with an artists paint brush and dish soap. When I replaced the new MAF with the old "bad" unit, it worked fine too. Apparently what happens is that crud just accumulates on the sensors and it quits doing its job. Hope this helps.