I will probably replace it anyway....so I know that isn't the problem. On the elbow, it was kinda crusty but I wiped it off with my fingers ( no cleaner) and visually inspected it. I might swap it out just to be sure.

She started right up today but yesterday after letting her run it was hard to start and acted like it was flooded. She still backfired today at idle then rpm would drop then it would pick back up. The backfiring sounds like popping the packs.
Any other ideas? With each step at least I know what it is not and by the time I am done it will be a new truck 😁

 

It sure sounds like it is running rich...... Try unplugging the front O2 sensor, (just in front of the cat) see if it runs any better.

Fuel trims both being at 0 though is kinda puzzling. Did you reset the computer in recent memory?

 

No cats on this truck. True dual into 18 inch packs. Just replaced computer a few days ago hoping it was the problem......it wasn't 🤔

I will unplug the O2 sensor and see

 

Unplugged O2 and it was the same. Truck again sounded stronger but rpm keep fluctuating at idle and with throttle. Still backfiring, but not as much or as loud. She is loud anyway.

 

Vacuum leak?? How's the plenum look?

 

Plenum looks and test good but I am going to replace all vacuum lines just to be sure. Have a few that don't look good going to the transfer case, so I might as well change them all so I know that isn't it.

I will let you know what happens but if you have any other ideas please let me know.

 

I think the next steps would be compression, and leakdown tests.......

 

I have replaced the coolant temp sensor.....no change. The intake manifold sensor....the plugs again ( they were all black)....the ignition coil....the tps..... and set the iac properly ( didn't realize they are adjustable....and fixed a vacuum leak at the transmission. It still ran terrible... running rough, backfiring but not as much. It died, I started it back up and it now idles great, no fluctuating of rpm, but it hesitates and pops under acceleration, but not when it is not in gear. Finally gave me a p1391 code. Same one it gave when this all started. Gonna recheck all the wiring. I believe it has to be electrical issue. Any ideas?

 

And rpms fluctuating when it is given throttle. It sounds like it forgets what to do for a split second....if that makes any sense

 

Cam or crank sensor, intermittent signal. Yep, that's gonna make it run like crap, if it even runs at all. Have you replaced the sensors? If so, what brand?