Just completed a 2000 mile round trip in my 2000 250k mile disco with non functioning 02's. Ran 194 degrees driving 75 mph in 100 degree heat getting 16.5 mpg. I would not worry about the sub-optimal fuel trims.

 

not sure really. could be a couple hundred miles.

if you can, you should reset the adaptive values. this would speed up the process as there would be no old "bad" data for the ECU to average with the new "good" data your O2's are providing.

 

@jastutte copy that. Sounds like I need to just put miles on it for it now.

@Extinct Yeah, great point. I probably need to stop over thinking it and just put miles on it. I'm just overly concerned about not repairing an issue that could cause harm long term.

 

As soon as I posted my last comment I drove the truck home and it started stumbling at idle.

It runs smoothly above idle, but the rpm fluctuates more than normal at idle and it seems to struggle to run. And the idle stumble is getting progressively worse.

it still starts fine and once moving does not seem to skip a beat.

Im suspect of the fuel pump at this point. No codes or SES yet.

 

SES code popped up, P0303, misfire on cylinder #3.

Plugs are new. Looks like I’ll digging into plug wire and coil packs.

 

This is disgusting.

I know you report in your most recent post that the engine is still stumbling at idle, but this is still disgusting. I hate for you that this happened to you. With all the things we recommend checking to track down vac leaks we never expect that the manifold isn't installed correctly. I guess we'll add that to the list.

 

@mln01 I purchased the truck from a forum member as well.

Woes continue, apparently the Vac leak was the beginning of my problems.

P0303

And pending codes: P0300 (multiple cylinder misfire), p0172 (bank 1 too rich)

This all seems to point to a malfunctioning or clogged fuel pump to me. The truck will run perfectly for a few minutes, and then stumble horribly, and the right itself again.

I could be wrong, but multiple cylinders misfiring and a Rich code, plus fuel trims being off, and a intermittent stumble sound a lot like a fuel delivery issue and not an isolated misfire.

 

Plugged fuel pump would not throw a rich misfire. Cyl 3 misfire is likely wire or coil. DIsconnect the oxygen sensors and see how it runs after you get the wire/coil changed. Start by swapping plugs/wires/coils left to right.

 

@Extinct I pulled the #3 plug wire while running and the truck starting misfiring noticeably. There is Definitely spark at the wire.

It’s interesting to me that the truck runs very smoothly, and then misfires seemingly at random, then rights itself again.

Is it possible for a general misfire due to a fueling issue to cause a SES for a misfire on a specific cylinder?

 

You don't generally get a misfire on a specific cylinder due to a general fueling issue. Bad injector, sure, but not plugged fuel filter or other general issue. Normal failure mode for coils is one plug starts to misfire, then its mate will start so that two on the same coil are bad. Easiest way to test is swap coil left and right. First I would consider swapping the plug with a different cylinder, then the wire, then the coil. Moving to a different cylinder is a better test for intermittent issues..