86longbed

This is in an 86 pickup. I rebuilt the engine last summer and it was running great. Lately it's been missing as the engine speed moves through the 1800-2500 RPM range. I recently replaced the cap, rotor, and wires in an attempt to fix the problem (did the trick a few years ago on a 4Runner) but there was no difference. I checked the signal gen. air gap in the distributor and took resistance readings on the TPS and MAF as I moved them through their ranges of motion. The TPS resistance changed in a linear fashion, but the MAF resistance did more of a zigzag thing. I checked a spare MAF I have and it gave me similar, though different, readings (and installing it didn't make a noticeable difference). I read an article HERE about taking MAF readings, but it doesn't say if the resistance change is supposed to be linear or if it bounces between about 200 and 900 a few times along its travel. I'd rather not spend $400+ on a rebuilt MAF if it's not the problem...Any ideas?

AH64ID

Did you replace the plugs too?

86longbed

They were new last summer. I checked them and they look good, but I didn't replace them. I probably should, huh?

AH64ID

There cheap... I do mine once a year...regardless of mileage...that reminds me since I haven't been home for 3 months I need to do them when I get there.

86longbed

Ok, a new set of NGK spark plugs are now installed and........No difference.

84sr5yoty

When is the last time you replaced the O2 sensor? That RPM range of miss you have usually indicates a bad O2 sensor.

86longbed

I just installed a brand new Bosch O2 sensor. Too bad it didn't help. But I do appreciate the suggestions. Keep them coming!

I'm starting to think that maybe there's a poor connection somewhere. But where? Other ideas are a bad pickup module in the distributor, bad ignition coil or ignitor, bad fuel injector(s), or bad MAF sensor (as mentioned earlier). Do any of these sound likely, or are there good ways to test them? I'm almost to the point of taking it in for a diagnostic, but I hate the idea of paying that much to have someone else find what I should be able to find myself.