The red line that barely moves is the Long Term Fuel trim.

Good to know on oxygen sensors. I won’t wast time/ money on that.

It seems to me like it’s essentially running rich like it does at cold start all the time. The way the truck idles, etc.

Do you think a smoke test is prudent @Extinct? A quality local shop can do one for me quickly and affordably.

I’ll look into ecu/ Bcu. Is that a common issue? I did notice when I wash the truck with a pressure washer (after off roading, I don’t spray the paint any close than 6 feet or so with a pressure washer) that there’s a very tiny leak at the top of the windshield.

No leaks even in super hard rain, but I saw it leak once after washing it. Also, it’s a sunroof truck and they have been resealed.

 

I will log IAT, STFT, and LTFT tomorrow.

Coolant temps are perfect. Sub 200 in all conditions. 190 or lower highway, 190-197 around town. 190-197 idle with AC on in the humid AL heat.

 

Another note that someone mentioned in an earlier post:

I do have a black exhaust tip. It does spit out what appears to be unburnt fuel when you rev the motor.

 

I knew the red line was LTFT, just could not tell whether it was using the left or right axis for the scale. On cold start it is lean, not rich. The LTFT being bottomed will trigger the codes you are getting, it says the ECU is trying to compensate for a lean condition but cannot. But the oxygen sensor readings and the stft suggest it is not a significant lean condition. I have seen ECU issues before, bad oxygen sensor drivers in my case but who knows. If it was mine, I might swap the ECU with my other truck first, as that is easiest. Then I might swap the lower intake wit one of my spares.

Also, you might want to consider borrowing the fuel pressure test kit from O'reily and testing fuel pressure, just to make sure there are no issues.

 

Gotcha. For clarification what all would you consider the lower intake? The intake manifold itself?

Fuel pressure would be a good thing to check. I have no idea if the pump/ injectors are working properly.

I will post my findings logging IAT, STFT, and LTFT.

 

Re: lower intake, yes the manifold, or I would potentially swap the injectors with another truck. I have the advantage of having five in the driveway and two complete engines in the shop, so it is easier for me. Now that I type this I would likely just swap the injector set as that would not require draining coolant. I don't really think it is likely to be injectors because normally both banks don't fail at the same time, typically it is one only. I suppose it could be leaking injector o-rings, which pulling the injectors would tell you. They are relatively cheap also.

 

Ah gotcha. I will post up the video of the new data logs shortly.

The truck has a slight stumble between 1800-2000 rpm. I thought it was driveline related, but now I’m thinking it’s related to the lean codes.

If the fuel pump is the culprit will it throw a separate code?

The truck had bad fuel in it, and it had to be pumped out right before I bought it (it had been sitting several months with bad fuel in the tank).

I am now thinking fuel pump and/or injectors are likely due to the way it’s behaving and all of your very helpful input!

 

STFT

LTFT

IAT

LTFT drops off the chart about 90 seconds in to the video.

 

A trustworthy local shop performed an intake smoke test, and fuel pressure test. They said there were no apparent intake leaks, and the fuel pressure was reading right where it should be.

Now that I have ruled out O2's, Intake Vacuum leak, and Fuel Pressure, it seems likely that the injectors are the culprit. The shop that diagnosed it mentioned that a coolant temp sensor could be reading erratically, although I see no evidence of that from the UG readings. Worth exploring?

I have an appointment with the Rover mechanic on Tuesday to further diagnose and likely test and replace injectors.

 

If the ECT sensor reads close to the thermostat I would rule it out. You can check it with a infrared gun if you like. If it truly is an injector issue, it woudl likely show up as one or two injectors that are not functioning, and the others are making up the difference. You can test it by removing the injectors from the manifold and cranking the engine while watching the injectors for spray. Of course the shop is just going to throw new injectors at it.