Hello all, finally was able to get some codes from the jag, turned it on this morning and the car was already in restricted performance. Used the scan tool and got P0171 and P0174. What's weird was that I did a hard reset and the car worked just fine again? Might be a sensor issue or something because if it was actually lean, wouldn't the issue persist no matter what? I believe this is what was causing the engine dying problems.

Hello... Try to spray contact cleaner on both connector of mass air sensor, located next to engine air filter, on air duct. You can try also bending a little bit all contact plots. Hope this help like for my XJR !!!

P0172 & 0174 often indicate a vacuum leak. There's plenty of places that air can leak into the intake system. You might try searching this site for these codes.

Yes air leak into both sides of the engine. Check the plastic intake duct work as the folded sections often crack down in the valley where you can't see it. Then depending on how the engine moves the leak can come and go.
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If there is an air leak, wouldn't I get "too rich" codes? Also, the codes and issues went away after unplugging the battery. I think it's an electrical issue.

You don't get too rich codes because there's more air than was measured by the MAF.

A codes clear or hard reset (power off) also clears all the OBD monitors.

The hard reset also clears the learned values (such as fuel trims).

If it runs "OK" then it's just that it can't flag DTCs till it manages to run OBD monitors successfully and has relearned things. (I.e. things are not OK just can't be flagged yet.)

It may be running OL (open loop) - check via OBD - and if it is then it adds excess fuel to protect the engine (but can damage the cats, which are cheaper than the engine).

Ah, that all makes sense. Let me check that.

I should mention there is also a whiny noise when the codes are not cleared.

Could be telling you it wants a fix ...

Lol maybe but in either case, could it be some kind of system calibration issue caused by the monitors? Like you explained, maybe there's an air leak, and the monitors don't "know" until they are ran for a while. Once they do they send the wrong signals to either the engine or transmission, causing the whiny noise? I hope its simply the noise of air somewhere.

All depends on what the whine is and where its coming from. Whines I usually associate with something belt driven like a power steering pump, AC compressor, pulley or even the supercharger. You can remove the belts and see if the whine stops or not and at least eliminate some things. Other than the supercharger though, a whining noise is not normal and is not part of the car relearning its parts or calibrating anything.

Uh oh. Yeah, my car isn't supercharged unfortunately. It is weird however, it has done the whine twice while on safe mode, once its off safe mode the whine disappears.

It could be the secondary air pump if you hear the whine on cold start.

These cars have air pumps? Also the whine matches the acceleration noise exactly. Up up down down.

Sorry for the lame humour. (Thankfully you got it, though.)

I don't know for sure but I'm a little doubtful it would be due to the unset monitors - but maybe.

Each incomplete monitor (apart from suppressing lots of codes) must have some effects which are a bit undesirable but exactly which causes what I don't know. Sorry.

All I can suggest is fix anything you can, see which monitors (if any) don't set, and investigate based on the drive cycle conditions for those monitors.

No worries at all lol, I appreciate a light joke

And yeah, it doesn't make much sense to me either. Sounds like its coming from underneath the car. Maybe its the noise of the safe mode gear?

Have you removed the belts and checked for the noise as posted above?
You need to that now and then post back.
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Haven't had time to do it after work but I will try tomorrow afternoon. It's my only day off lol

Two major cracks in the intake system, and oil and dirt in it. Clearly the air filter isnt the main source of air for this thing.

Sealed the holes (temporarily) with high temp tape to see if that would help. The car ran good enough that I felt safe to take it on the highway. Drove two towns away (20 miles) and back with no issues. No codes, nothing. Got home, shut it off, turned it back on several times, and still nothing. Maybe that was the issue. BUT now I heard that the car is backfiring. I swear, it's one issue after another with this thing. Luckily I've got the energy to fight this uphill battle lol.