M52TU IDLE Problems

[sebe20]

Hello Community,
My M52TU swapped E30 has a massive problem with the idle. It's an M52TU28B from a E46 328Ci with custom tune on a MS42 ECU. Engine has a M54B30 intake manifold, M54B30 DISA Valve, M52 Throttlebody and Idlecontrolvalve.

When the engine is turned on it fires right up and idles at 5000rpm! No missfiring, no surging, just runs happily at 5000rpm straight. When i disconnect the ICV plug, it goes to idle at approx. 800-1200rpm but runs really rough and wont take any gas!

I tried to clean the ICV with brake cleaner, it opens and closes fine, just stays fully open when engine is turned on.



Stuff i tried already:

• ICV cleaned
• CCV replaced
• vacuum hoses replaced
• injection valves swapped with a different set
• DISA valve rebuild
• Airmassflow sensor swapped (now i have 3 different brands to swap around)
• intake hoses replaced
• checked if throttlebody is closed at engine start (is completly closed)
• reset the adaptions in the ECU with INPA

Only two codes are thrown by the ECU:

• throttlebody position not found
• thermostate temperature not plausible

Any help is much appreciated!

Greetings from Bavaria,

Sebastian


PS: i ordered a replacement ICV yesterday...

[pazi88]

How can you use m52thorttlebody with ms43 from m54? Those will not work together so I would suggest that is yor cause of problem. M54 is totally drive by wire and m52tu is only partly drive by wire and those can not be mixed.

Why you just don't use ms42 from m52tu and all would work perfectly.

[sebe20]

How can you use m52thorttlebody with ms43 from m54? Those will not work together so I would suggest that is yor cause of problem. M54 is totally drive by wire and m52tu is only partly drive by wire and those can not be mixed.

Why you just don't use ms42 from m52tu and all would work perfectly.

Thanks for the reply,
the tune on the ECU was matched with the parts specifically used in the build. The ECU checks the position of the throttlebody as far as i know it wouldn't matter if it's a drive by wire or mechanical throttlebody as long as the values of the TB are correct That's at least what i got told when troubleshooting the issue with the tuning company.

After some back and forth i got the company that did the tune on the ECU to send me a replacement MS42 ECU with exact same tune on it just to be sure. Also i made a mistake, it's an MS42 not an MS43, was not able to tell via label since it got re-labeled by the company where it came from... will correct in first post later on. :fishslap:

[pazi88]

Well that's fine then. But that fault code suggests that the thorttle body is the broblem. As I said the m52tu thorttle body is partly drive by wire. Ecu has some level of control for the thorttle flap, even when there is cable for that also. So that 5000rpm idle is because some problem in thorttle body. If you disconnect icv, ecu goes to limp mode and stops controlling thorttle flap. Which point it is only mechanically driven. And yes in limp mode it behaves just like you described.

[sebe20]

Well that's fine then. But that fault code suggests that the thorttle body is the broblem. As I said the m52tu thorttle body is partly drive by wire. Ecu has some level of control for the thorttle flap, even when there is cable for that also. So that 5000rpm idle is because some problem in thorttle body. If you disconnect icv, ecu goes to limp mode and stops controlling thorttle flap. Which point it is only mechanically driven. And yes in limp mode it behaves just like you described.

Was able to confirm that the throttlebody is partly drive by wire since it opens a little bit when ignition is turned on. Also found out that the second set of injection valves have different ohmage and flow rate.


Currently im using the OEM Siemens (purple) ones, rated at 240ccm at 12 Ohm. Second set i used for testing where Siemens (black) 215ccm at 14 Ohm... Didn't change the rpm at all as i stated in the first post, just curios how they where sold as E46 328i injection valves



Could a huge Vacuum leak from the brake booster cause that high idle? I've seen some videos on youtube where the 2.8l manages to idle at 3000 rpm with a vaulty CCV and 2500 rpm with a leaky brakebooster. Currently i use a used 525i pandem brake booster with mercedes master cylinder which seems mechanical to be fine.


Back to the issue with high rpm, a tb would be really expensive looking at 700 - 1k€ Used ones go for 250€... but i don't want to risk gambling with a used unit

[pazi88]

The thorttle flap shouldn't open at all when you turn on ignition. It should stay closed. Even when you press little bit thorttle it should stay closed. On very low thorttle positions m52tu uses only icv to rev up engine. So that points even more to faulty thorttle body. Have you made sure that the electric connector to thorttle body is clicked in all the way. If you don't fully rotate the connector to locked position, it causes all kinds of throttle flap problems.

[sebe20]

So i got a friend to read the analog values via inpa, see picture.

The throttlebody only opens a little when ignition is turned on, closes when engine is cranked.
When throttle is pushed a approx. 25% the value of the ICV goes up by 2%. This depends on how much the throttle is pushed, the value can increase up to 92%

[sebe20]

So I swapped the icv today, car went straight to limp home mode. Since I got some cheap China massairflowsensors I swapped the OEM with one that got static resistors in it. Car seems to idle OK. Not what I would call perfect but at least doesn't go to 5000rpm or limp mode. Any suggestions what brand of maf I should purchase? I can get from 50 to 300€ like ten different brands here.
Thanks so far for the help

[sebe20]

So I swapped the icv today, car went straight to limp home mode. Since I got some cheap China massairflowsensors I swapped the OEM with one that got static resistors in it. Car seems to idle OK. Not what I would call perfect but at least doesn't go to 5000rpm or limp mode. Any suggestions what brand of maf I should purchase? I can get from 50 to 300€ like ten different brands here.
Thanks so far for the help

Got myself a VDO (Siemens) original one. The engine now dies instantly, mixture seems too rich.




So, the car has been sitting at a shop for almost 2 Months. They made a duplex stainless steel exhaust aswell as making new brake lines.
The car still idles like shit. When i get the car back i'll swap in the original M52TU28 intake manifold aswell as injectors. Seems the guy i got the ecu with mapping on is a shithead and did not change anything mapping and intake wise. :rippedoff:

Side note: i love the work they did on the exhaust... even wrapped it up in heatshielding tape and even with rough idle sounded sweet

[pazi88]

When doing m54 intake swap there needs to be sealant between the adapter flange and the intake. If not I can say from experience that the engine will idle like piece of shit :D

[sebe20]

Double post

[sebe20]

When doing m54 intake swap there needs to be sealant between the adapter flange and the intake. If not I can say from experience that the engine will idle like piece of shit :D

Interesting information mate, I'm not sure anymore if it had one. But I made sure to tighten it and adding sealant.
Currently it won't take any throttle at all

It's this one, don't think I put sealant on the throttle body itself

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.de%2Fulk%2Fitm%2F122894795122

Since i'm already searching for vacuum leaks, i decided to order some parts which i still think could be also be damaged. (see below)

[pazi88]

Same part. The throttle body has it's own seal so it doesn't need sealant. but the back side of that adapter needs it and at least our instructions were missing the step of adding sealant there :D

Is it giving any fault codes?

[sebe20]

Same part. The throttle body has it's own seal so it doesn't need sealant. but the back side of that adapter needs it and at least our instructions were missing the step of adding sealant there :D

Is it giving any fault codes?

I've put sealant on the adapter plate around the o-ring since it seemed to be insufficent at the time. Used some Elring sealant...



It throws a bunch of codes, the only one i have right in my head is code 8: Signal MAF Short circuit -> screenshot from inpa

[pazi88]

Well that's then quite clear. It's still maf problem. The engine won't run normally untill you can get rid of the maf fault code. Or of course the ecu could also be broken. Test with 100% working maf from running car. If that doesn't work, ecu is broken. (Or wire is broken somewhere).