4.8i Behaving Strangely - Codes

[ard]

Originally Posted by thesamiest

I have another manifold lying around somewhere might try that sensor until a new one gets here. I asked to check for air/vacuum leaks and they confirmed that it was not it, but i might have to stick around and see how they're performing those tests and push them to do it again.

IMO this will turn out to be your issue.

If you had a hard parts failure it would stay failed. A cracked hose/air leak can come and go.

As the crack/leak continues the symptoms become more consistent

[scourtaud23]

Have you tested the codes while it was ok or while it was at its worst?

I'm also thinking its a vaccum issue since that would be one of the only things that can affect just about everything on the car.

[thesamiest]

Originally Posted by ard

IMO this will turn out to be your issue.

If you had a hard parts failure it would stay failed. A cracked hose/air leak can come and go.

As the crack/leak continues the symptoms become more consistent

I keep brining leaks each time i send it at the shops, they either don't believe the issue to be that simple or have not been testing it properly. I changed the battery a couple of months ago and surprise, they did not register it. I inquired as i felt the new battery was not performing optimally.

[thesamiest]

Originally Posted by scourtaud23

Have you tested the codes while it was ok or while it was at its worst?

I'm also thinking its a vaccum issue since that would be one of the only things that can affect just about everything on the car.

Tested it when it was behaving completely normal and tested it when it was erratic. If the codes are erased they might stay away for a short while until the car acts up and again they all show up.

[scourtaud23]

You need to find someone that will smoke test it in front of you or you can buy a spray can of starter fluid and spend some time looking for leaks but you might need some software to see it register (INPA, OBDII or even TestO (I really like this one as it is way faster than INPA and can read almost every sensor)

[thesamiest]

Update

I’ve looked further into the issue and the issue got “fixed” at least for 600miles ( which is a lot as I couldn’t drive more than 1-2 miles without it going into limp mode and the car behaving erratically ) , but i didn’t call it fixed as i had a feeling it could come back up, and it did. What fixed the issue for the 600 miles was replacing the differential pressure sensor (again, the previous one was from another manifold of the car i had laying around), the car started behaving completely differently, it reved differently and picked up speed much more quickly and generally felt less bogged down thus the transmission worked better. However two codes remained:
2B70 - Variable Induction Mainfold
29F5 - Catalytic Converter conversion bank 2

I suspect that the catalytic converter has been shot due to the rpms jumping up and down at time which seems like a misfire. I was present during the smoke test and there were no apparent leaks.What could be the cause for the differential pressure sensor to go bad this quick? The car has been now through three of them, a new one will remove all the codes expect the 2B70 - Variable Induction Manifold and the 29F5 - Catalytic Converter bank 2. Might the manifold be the culprit?

[ard]

DO NOT jump to a conclusion about your CAT.


A very rich running car will have your symptoms....

[thesamiest]

Originally Posted by ard

DO NOT jump to a conclusion about your CAT.


A very rich running car will have your symptoms....

You're right, i was just assuming it as that's not on the repair list right now. Since the only code that was remaining was the Manifold after the differential pressure sensor was changed, i'll look into it further.

[ard]

How are your short and long term fuel trims????

Look up some posts by Alphabeta in the last two months about this.....

[wsmeyer]

When you say "throttle harness" are you talking about the connection to the throttle body?

If not, check out this page of RealOEM:

RealOEM.com - Online BMW Parts Catalog

I occasionally have some weird thing where the engine seems to stutter. I ran across that a while back and the part was $19 so I did it. Didn't help me though.

Mine is so infrequent it has proved impossible to track down. I even purchased a BluDriver so I could log everything but even in the logs I can't spot anything fishy when it happens.