4.8i Behaving Strangely - Codes

[thesamiest]

The car is going into limp mode, has fluctuating rpm's, sometimes they drop below 500 at idle and quickly jump back to above 500. (Car idles at around 560-580rpm) Around 1500rpm sometimes it jumps 500 rpm's up or down, not noticeable above 2500 rpm. The 4x4 malfunction, abs etc light up, sometimes the engine malfunction warning comes up and the car behaves erratically. (Had previous threads on this, changed the battery, throttle harness, throttle body, gas pedal, etc). Car stutters when driving slowly and there is an upshift, from around 1000rpm to 1500 rpm the car stutters. The big (500 rpm up or down) jumps usually/most often happen on incline. Also the car generally feels bogged down. The warnings and limp mode, erratic engine behavior can go away for hundreds of miles and come back, no noticeable pattern.


Checked for codes and these keep coming back:

2D32 - Differential pressure sensor, plausibility error
29F4 - Catalytic Converter Conversion
2B70 - Variable Induction Mainfold
29F5 - Catalytic Converter conversion bank 2

Where i live 99.97% of the X5's are diesels, few petrol engines, and theres my 4.8i. So the dealership and shops usually give me a hard time with this particular issue and did not know what to do with it. Any suggestions?

[BGM]

I recall on this I recommended checking the DME unit. Have they looked into that ?

[thesamiest]

Originally Posted by BGM

I recall on this I recommended checking the DME unit. Have they looked into that ?

Yes i looked into your suggestion and pushed the dealership and a few BMW shops around to look into it and they all claimed it's fine.

However if there's no other solutions, they've thrown enough parts at it might as well throw in another one and see if it resolves it.

[Skyline]

Since you're getting a code from the differential pressure sensor, have you tried replacing that? It's in a bitch of a spot to get to mounted to the rear of the manifold, but it's a hell of a lot cheaper than a DME at around $85.

Also, if it is working properly, and giving such a code, have you confirmed that everything is properly sealed up? No air/ vacuum leaks? You might want to plug the throttle body and smoke test using a fitting to put smoke into the oil filler cap. Unmetered air can cause all sorts of drivability issues. BTW Blue Point (sold by Snap-on) sells a stretchy blue rubber universal oil cap with a fitting to attach a smoke machine in the center of the cap that does work with our cars.

[thesamiest]

Originally Posted by Skyline

Since you're getting a code from the differential pressure sensor, have you tried replacing that? It's in a bitch of a spot to get to mounted to the rear of the manifold, but it's a hell of a lot cheaper than a DME at around $85.

Also, if it is working properly, and giving such a code, have you confirmed that everything is properly sealed up? No air/ vacuum leaks? You might want to plug the throttle body and smoke test using a fitting to put smoke into the oil filler cap. Unmetered air can cause all sorts of drivability issues. BTW Blue Point (sold by Snap-on) sells a stretchy blue rubber universal oil cap with a fitting to attach a smoke machine in the center of the cap that does work with our cars.

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.

[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

[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 Skyline

Since you're getting a code from the differential pressure sensor, have you tried replacing that? It's in a bitch of a spot to get to mounted to the rear of the manifold, but it's a hell of a lot cheaper than a DME at around $85.

Also, if it is working properly, and giving such a code, have you confirmed that everything is properly sealed up? No air/ vacuum leaks? You might want to plug the throttle body and smoke test using a fitting to put smoke into the oil filler cap. Unmetered air can cause all sorts of drivability issues. BTW Blue Point (sold by Snap-on) sells a stretchy blue rubber universal oil cap with a fitting to attach a smoke machine in the center of the cap that does work with our cars.

Changed the differential pressure sensor, i haven't checked for codes yet but the car is behaving the same with the bucking and hesitation but limp mode is getting activated much more frequently. I also noticed the car was needing much more frequent refills, calculated it and on average it's getting 8.2mpg, on a good day 9mpg, this is normal driving with a few pushes here and there. The Catalytic Converter conversion bank 2 error came up last time randomly, might it be an oxygen sensor that is bad, but not bad enough for it to throw a code?

[X5chard]

My 4.8 had some higher than normal rpm issues, sent it to shop but they couldn't find anything, smoke tested but no leaks. No idea what's going on. I bought another car now, I think I am going to sell it off now, I give up.

Sent from my SM-N910F using Tapatalk

[thesamiest]

Originally Posted by X5chard

My 4.8 had some higher than normal rpm issues, sent it to shop but they couldn't find anything, smoke tested but no leaks. No idea what's going on. I bought another car now, I think I am going to sell it off now, I give up.

Sent from my SM-N910F using Tapatalk

I’m getting close to that point now. Mind asking what car did you choose.