M50 Power loss on part throttle car now dead...

[goosiegander]

Hey guys,

Appreciate some input here

The M50 Vanos EWS 1996 2.5 in the e34 is playing up.

A full day of messing about swapping parts and reading codes no joy,

At idle there is intermittent rough running and placing anything other than gentle load between idle and 3000 rpm results in missfire/hesitation.

Injector rail and injectors swapped, spark plugs, fuel filter, vacuum hoses (they were fu*ked) MAF swapped, Throddle body and TPS swapped.

Only codes thrown were TPS and Knock sensor.

Was thinking a bad dose of fuel but now the filter has been changed after 20 liters of v-power after being run down to fumes this seems less likely to me,

Hoping it's not the ECU as don't want to be arsing about swapping lock barrels and so on.

Collective wisdom appreciated, pi**ed off that this is happening on a 100k car...

Cheers guys,

Chris

[DanThe]

If you can read the fault codes its not likely to be the ECU. Do the codes come back straight away after clearing? Any more info on the fault codes?

[goosiegander]

codes cleared ok Dan just tps and knock according to Nathan,

Cam and crank sensors we not touched along with the inlet temp sensor,

Car behaves slightly better with aircon and/blower/radio off.

Earth to fuel pump was checked and even bypassed to no avail...

Fuse 25 had melted but now replaced and no improvement

[goosiegander]

Well cue the heat and the engine is dead...

Over fueling and idling like a pig,

Won't rev whatsoever,

Does now seem to be a definite correlation between temp and level of wrongness...

[goosiegander]

Bump this is urgent now guys

[DanThe]

Blue sensor been changed?

[goosiegander]

Blue sensor been changed?

Still waiting on a fresh one Dan,

Is there a diagnostic i can run on the sensor or associated wiring?

[DanThe]

You can bridge the terminals but its not ideal

[daimlerman]

I cured my M50 of poor running issues by adding an extra earth cable from the engine mount back to the battery,I understand that the ECU runs some odd voltages and needs a perfect earth to operate properly.

As I seem to remember that E34 hides it's battery under the rear seat,could corrosion at the battery earth/engine earth strap be the root of your problems?

[goosiegander]

Certainly worth a look while I'm waiting for the new temp sensor Malcolm,

Thanks for the help guys, now using the moordoor as a daily until this is resolved...

[DanThe]

Good point about the battery Malcolm, corrosion on the + fuse block is common on E34's with the battery under the seat

[goosiegander]

Swapped the battery at lunchtime,

Momentary good start dropping down to the sub 500 rpm idle, contacts are ok.

Guess I'll see what the temp sensor does...

[DanThe]

Is the alternator charging properly?

[goosiegander]

Presume so Dan as old battery didn't discharge itself or start with any issue.

Where should I be positioning my multimeter to check charging voltage?

[daimlerman]

Battery terminals.
You should get 12v + with the engine off,13.8-14.4v with the engine idling.

With reference again to the earth straps,one that tests fine for continuity may well not carry current properly under load.

[goosiegander]

Battery terminals.
You should get 12v + with the engine off,13.8-14.4v with the engine idling.

With reference again to the earth straps,one that tests fine for continuity may well not carry current properly under load.

Indeed so, will give it a go after work and report back, thanks for that!

[penton08]

For clarity neither the Tps or the knock sensor codes came back again, I assume the Tps had been unplugged at some time and the knock sensor fault is a result of the misfire. Voltage read a steady 13.5 to 14 volts while being driven.

[goosiegander]

For clarity neither the Tps or the knock sensor codes came back again, I assume the Tps had been unplugged at some time and the knock sensor fault is a result of the misfire. Voltage read a steady 13.5 to 14 volts while being driven.

Much appreciated Nath,

Hopefully the appearance of the blue temp sensor replacement tomorrow will change things...

Thanks again for the contributions guys

[bmwbmwbmw]

i had exact the same problem on my e39, i changed plugs, filters, coil packs, maf, and still had the same problem, every time i got a diagnostic it came up with tps and knok sensor, replaced those cleared the codes and still was no good, stuck it back on the diagnostic and it still came up with tps and knok sensor but only this time with a new one, the vanos. at that point we changed the cam sensor cleared the codes and to this date she runs like a dream, worth a try on yours matey

[goosiegander]

Blue temp sensor replacement had no effect,

Cam sensor it is...

[goosiegander]

Have now swapped cam sensor and vanos solenoid, no joy, starts up and idles high for a couple of seconds before descending to sub 500rpm idle and dieing...

Have Lambda sensor turning up tomorrow but that's the last thing before it goes to the machine shop for compression test...

Any last ditch thoughts?

[DanThe]

You can unplug the lambda and it will run in limp mode, but it should run stable. Sounds like it could be an ecu fault TBH, worth finding a non EWS one to try out

[goosiegander]

You can unplug the lambda and it will run in limp mode, but it should run stable. Sounds like it could be an ecu fault TBH, worth finding a non EWS one to try out

Thanks for that Dan,

Will a non ews ecu work on an EWS loom?

Tried Steve's and couldn't start it...

[DanThe]

Yes it will work, should fire straight up, I take it it was cranking and behaving the same way?
Hows the fuel pump?

[goosiegander]

Nothing at all with Steve's ecu, just cranking, not even a hint of firing at least with mine it started and drove, until it gave up...

Fuel pump i suspect is fine as there was a shit load of fuel dumped out when it did run, it stank the garage out and thats with the door open from a few feet away!

Will swap the ICV tomorrow in there interests of thoroughness and also see if i can release the spare fuel pump from the tank Steven has kindly lent me...

Any other thoughts?

[DanThe]

Defo a non EWS ECU? Will have a red label if so

Its worth checking the pump, as they rarely just stop working, its usually a slow and painful death

[bmwbmwbmw]

has you car got a cat, i could be wrong, but when i had the problem on my e39 i did read somewhere that if the cat is blocked than it will course issues, try removing it than start the car, see if there is any difference