2008 Z4 - N52 rough idle and MAF fault codes

[BambaRamba]

Hello everyone. New member an newly minted Z4 owner here, although I do a Z3 as well...

I recently bought a neglected 2008 Z4 3.0si, 160k miles - it was listed with engine issues but was real cheap and I figured it will be an excellent project for me and my son. What can I say - I am a sucker for old cars that need fixing.

It starts and drives but has a bit of a rough idle and noisy valve lifters. Checked compression and it is 220-230psi on all cylinders. I read that the best medicine for noisy lifters for a car that has been sitting around is a spirited drive and a few trips past 3.5k RPM but have not done that yet.

Pulled codes with Foxwell NT530:
2F9A - DME: Outside-temperature sensor, communication
2A17 - DME: DMTL, system fault
2D29 - DME: Differential-pressure sensor, intake manifold: plausibility
2A2F - DME: Mixture control 2
2A2E - DME: Mixture control

I have not had an N52 before so I am really looking for pointers and suggestions. Here is what I have done so far:

Checked the temp sensor - it was missing

. Ordered a cheap amazon replacement and plugged it in - the code remains and dash still shows -40f. The wiring must be nicked somewhere but have not had a chance to trace it. Is this sensor material enough that its absence can impact the idling?

Checked the voltage on the O2 sensors. Pre-cats were at just over 2v, post-cats were 0.5v-0.6v. It appears that they are fine?

Read up on 2a2f and 2a2e - the MAF sensor appears pretty new, it is the DL-3089 variety which is the Autozone sensor that a few people on the forums seem to have had a good experience with. I also read about the MAF plug and ordered the replacement parts and contact cleaner. It will be a few more days before I get them...
I have not done a smoke test but plan on doing one at the first available opportunity.

I will leave the DMTL for later - unless you tell me that it is related to the airflow/MAF/leaks issues the other codes seem to point to, I really want to address the issues in the engine bay before investigating the pump and canister.

Lastly, what about the MAP sensor error, 2d29 - is this related to the MAF/mixture codes or is it a separate issue? None of these parts are very expensive but I don't want to order a bunch of new parts before I confirm that they are really needed...

So, I have a few things going on, very much appreciate your thoughts and suggestions. How about this for a first post

 

[BumpyZ4]

One thing is the pre-cat O2 sensors should constantly oscillate somewhere between 1v and 0v. I've never seen O2 sensors go above 1v on any car. Post-cat O2 sensors should stay constant around .5v if the mixture is correct and the cats are doing what they are supposed to do.

 

[RobbiZ4]

Pulled codes with Foxwell NT530:
2F9A - DME: Outside-temperature sensor, communication
[...]

1. Checked the temp sensor - it was missing.
2. Ordered a cheap amazon replacement and plugged it in
3. the code remains and dash still shows -40f.

1) Why? Perhaps because more is missing or damaged in this area if there has been a previous crash.

2) Not the best idea, as the original ones are not that expensive. Always make sure you use original parts for these engines!
3) Temperature is a very important piece of information that almost every control unit relies on. If missing, it may have side effects on different functions as well as the DME.

The temp sensor is connected directly to the dash (KOMBI instrument), which provides it's data via CAN-K to all the other ECU's.
Should be a starter, as the other codes might be a follow up issue. Not sure, but temp.sensor should be the "easiest" step.

 

[BambaRamba]

Thanks for the input guys.
RobbiZ4 - It has been in a slight encounter with a parking curb or something, the piece to which the temp sensor attaches to is missing. I ordered the amazon piece because it was very cheap and came quickly and included a connector. I have removed the air box to do a smoke test tomorrow and now have easy access to the wiring so i plan on checking and tracing the wires. Do you happen to know the fuse for the temp sensor? I will look to see if i can find the wiring diagrams...

BumpyZ4 - while I am new to the Z4, i looked up several forums and videos and they all indicated the pre-cats should be 2v - 2.1v. Where have you seen that they should be 1V or below?

 

[RobbiZ4]

Do you happen to know the fuse for the temp sensor? I will look to see if i can find the wiring diagrams...

As said:

The temp sensor is connected directly to the dash (KOMBI instrument), which provides it's data via CAN-K to all the other ECU's.
Should be a starter, as the other codes might be a follow up issue. Not sure, but temp.sensor should be the "easiest" step.

There is no individual fuse in place. The Kombi itself is powered up by F74.

Just measured the temperature sensor on my Z4-Tower:

5.9 kOhm @room temperature ~22°C.
The value lowers when warming up with my fingers.

 

[BambaRamba]

Thanks RobbiZ4 - I found the wiring diagrams and saw there is no fuse but it all ended up being unnecessary...
The temp sensor turned out to be a worn out connector, the tab was not holding the sensor in place. Since the $10 amazon temp sensor came with a connector, I quickly replaced it and the temp sensor is now operational.

Did a smoke test and did not find any leaks. I am not counting this as 100% confirmation of no leaks because i used diy redneck smoke device... The engine was pressurized, there were no leaks visible, and when i would open the oil fill cap the pressure releases and smoke comes out of the oil fill opening.

Since I had the intake tubes/box out, i used the opportunity to work in space and replaced the MAF sensor connector body and grommet and cleaned the pins, then lubricated them...

After all this, all DME fault codes are gone - have not driven the car but let it idle for 20min and codes are not coming back...

So idle is now good, but now it is obvious that I also have a knocking sound that indicates a mechanical problem. I was attributing it to the rough idle but it seems it was a separate issue... Will post a short video with sound shortly.

I appreciate the help!

 

[BambaRamba]

Here is the knocking sound I am talking about... My gut feel is to check the timing chain and guides, but those are just my first thoughts. Any pointers on where to start with diagnostic?
N52 knocking sound

 

[BumpyZ4]

BumpyZ4 - while I am new to the Z4, i looked up several forums and videos and they all indicated the pre-cats should be 2v - 2.1v. Where have you seen that they should be 1V or below?

Here are the BMW O2 Sensor specs. BTW how are you measuring the voltage at the sensors?

 

[BambaRamba]

Thanks BumpyZ4 - since I have no codes whatsoever I am leaving the o2 sensors out for now. Doing a quick search i saw a few people mentioning the voltages you posted but also saw others sharing INPA/ISTA screenshots showing ~2v for the pre-cats... I have bigger fish to fry so unless I see a code I will be investigating later.

Regarding the noisy engine, i am leaning towards replacing the timing belt tensioner first - my research seems to indicate that if there was a bigger issue with the timing chain I would be getting fault codes. Does that sound right? I am definitely looking for thoughts and suggestions on this topic...

I idled the car for 20min with occasional revving and still clear. The engine is very noisy as seen in the video above but idle is steady at ~700rpm and other than the noise the engine is running smooth. No codes.

My foxwell nt530 can't measure camshaft offset or adaptations (or at least I was not able to find them) so I will try to get ISTA set up next week. The NT530 is great little tool but nowhere close to INPA/ISTA obviously...