M52 Engine running rough

[Ch4ni]

Hi,
I could do with some help in narrowing down a couple of issues I am having with my M52B28 conversion. I recently completed an M52 conversion with M50 inlet manifold, I have 2 issues;

1) the engine starts but runs rough sound like it is misfiring. I have checked spark plugs, cleaned these and also replaced the coil packs as well, this has made no change to the running of the engine. What can I do to check to see which if any of the cylinders are causing the misfire or what is causing this?

2) New water pump with 88 degree thermostat has been fitted during the conversion. I bled the water system with warm air coming into the cabin. After a couple week of starting the engine the warm air is no longer coming and the engine is getting hot, what is causing this and what can i do to resolve this issue?

Any help is fixing this issues is great;y appreciated.

[Brianmoooore]

The first thing to do is to read the diagnostics. You can buy a little bluetooth device on ebay for about £4, used in conjunction with a free app. on your 'phone.

[Ch4ni]

I have iCarsoft Scanner i910 I can plug this in and post here the diagnostic results I get from the DME module. Do I read the codes while the engine is running or with the engine off?

[Ukhozi]

I have iCarsoft Scanner i910 I can plug this in and post here the diagnostic results I get from the DME module. Do I read the codes while the engine is running or with the engine off?

Ignition on, engine OFF.

[DanThe]

If it is a cylinder down then simply unplug the coils one at a time, the engine running will not change when you unplug the affected cylinder.
If the heater is not blowing hot then you have an air lock

[Brianmoooore]

If the heater is not blowing hot then you have an air lock

Or the hoses are the wrong way around, and the heater valve has given up the reverse flow struggle.

[Ch4ni]

Thank you all for the feedback, I connected the diagnostic scanner and got the following codes from the DME;



I replaced the spark plug and coil pack, this made no difference the engine still rough. I put the scanner in again and this time it came with Cylinder 1 did the same and made no difference.

Over the weekend I noticed the following with the running of the engine, from cold start it takes a bit of time to start once it running it runs rough and as ti warms up it get a bit smoother running, but when completely warm, the engine struggles to rev also struggles to run, eventually the engine cuts out and will not start again until it has cooled down.

I removed the plug and can smell fuel, it looks as if it is running too rich. Could this be leaky fuel injectors?

I really can do with help in what I need to do next in find the cause of this issue.

BTW, the hot air is now flowing through the car look like the air lock is gone so all good there, just need to sort the engine running issue.

[Brianmoooore]

I replaced the spark plug and coil pack, this made no difference the engine still rough. I put the scanner in again and this time it came with Cylinder 1 did the same and made no difference.

Did you clear the fault codes between tests?

Over the weekend I noticed the following with the running of the engine, from cold start it takes a bit of time to start once it running it runs rough and as ti warms up it get a bit smoother running, but when completely warm, the engine struggles to rev also struggles to run, eventually the engine cuts out and will not start again until it has cooled down.

This is usually associated with problems with the coolant temperature sensor. The original is not compatible with the E30 temperature gauge, so changes will have been made to the sensors. Are you sure this has been done correctly?

I removed the plug and can smell fuel, it looks as if it is running too rich. Could this be leaky fuel injectors?

No reason to suspect them yet.

[Ch4ni]

Did you clear the fault codes between tests?

Yes cleared the codes each time.

This is usually associated with problems with the coolant temperature sensor. The original is not compatible with the E30 temperature gauge, so changes will have been made to the sensors. Are you sure this has been done correctly?

Yes I believe this has been done correctly I fitted E30 temp sensor on the cylinder head, I removed the brown/purple wire from the 4 pin E36 temp sensor and connected this to the E30 one. The temp gauge is working in the car and responds when the thermostat opens when the temp is reached. Also the original E36 temp sensor is also fitted to the cylinder head

[Brianmoooore]

Yes I believe this has been done correctly I fitted E30 temp sensor on the cylinder head, I removed the brown/purple wire from the 4 pin E36 temp sensor and connected this to the E30 one. The temp gauge is working in the car and responds when the thermostat opens when the temp is reached. Also the original E36 temp sensor is also fitted to the cylinder head

Sounds correct, but I would check at the ECU plug as the next step.
Disconnect the plug from the ECU, measure the resistance between pins 10 and 39 with the engine cold, then reconnect the plug, run the engine up to full temperature, then quickly remove the plug and measure the resistance again.

[Ch4ni]

Sounds correct, but I would check at the ECU plug as the next step.
Disconnect the plug from the ECU, measure the resistance between pins 10 and 39 with the engine cold, then reconnect the plug, run the engine up to full temperature, then quickly remove the plug and measure the resistance again.

I will get these measurements and post them here. Just for information what values do I expect to see when cold and hot? What will these measurements tell you what is happening with the engine?

[DanThe]

Check the ECU for corrosion, these had a habit of getting soaked with water when fitted to an E36 due to poor drainage from the windscreen trim, one of the popular failures is the transistors that fire the coils

[Ch4ni]

Check the ECU for corrosion, these had a habit of getting soaked with water when fitted to an E36 due to poor drainage from the windscreen trim, one of the popular failures is the transistors that fire the coils

The ECU came from the running donor car that I was using until I broke it up to put the M52 in the E30. It was running without any issues.

I will open up the ECU and check for corrosion this weekend.

[Ch4ni]

I like to thank you for all you help, I believe I have resolved the rough running of the engine;

Sounds correct, but I would check at the ECU plug as the next step.
Disconnect the plug from the ECU, measure the resistance between pins 10 and 39 with the engine cold, then reconnect the plug, run the engine up to full temperature, then quickly remove the plug and measure the resistance again.

I did the cold measurement which was 2.77k, did not manage to take the reading when hot as the engine ran without an issues.

Check the ECU for corrosion, these had a habit of getting soaked with water when fitted to an E36 due to poor drainage from the windscreen trim, one of the popular failures is the transistors that fire the coils

I opened up the ECU and there is no corrosion very clean inside.

What I did to fix the issue, I suspected the issue to be with the fuel injectors, I removed the fuel injectors, on one of them I noticed the electrical pin was bent and did not seat correctly onto the connector. I straighten this and proceeded to refurbish the injectors and replace all the "O" rings. Re-installed the injectors and ensured the electrical connectors were fitted correctly onto the injectors.

Started the engine and instantly the engine ran smooth took it up to operating temperature, electric fan came on to cool the radiator, the engine runs smooth and does not turn off like it did previously when getting up to temp.

[boiliebasher]

Well done mate. Hopefully that's it sorted now!

[Ch4ni]

Over the weekend I took the car out a run, I have noticed that when accelerating under load the engine misfires, when I come off the pedal it runs fine. Could anyone advise what would be causing this issue under acceleration?

The M52 is fitted with M50 Inlet Manifold and running on the stock DME that came with the donor car. Could this be causing this issue?

[Brianmoooore]

Get yourself one of these: https://www.ebay.co.uk/itm/OBD2-ELM327- ... SwEmxfHC86 (loads available on ebay) and download a free app. onto your 'phone called car scanner, and you can observe live data while you drive, as well as see any codes that have been logged.
This should give firm clues as to what's happening, rather than guesses.

[Ch4ni]

Get yourself one of these: https://www.ebay.co.uk/itm/OBD2-ELM327- ... SwEmxfHC86 (loads available on ebay) and download a free app. onto your 'phone called car scanner, and you can observe live data while you drive, as well as see any codes that have been logged.
This should give firm clues as to what's happening, rather than guesses.

I bought this unit, and downloaded a couple of apps EODB Facile and inCarDoc Pro both of these connect to the ELM327 but not able to establish a connection to the DME. I will try the Car Scanner tool and let you know what I get?

[Ch4ni]

I have also would like some advise, I have 20pin ODB connector and use a 20Pin to 16 pin ODB2 cable to connect the diagnostic tool. Looking at this https://boyanmilushev.wordpress.com/201 ... ii-pinout/ the cable I have is not wired as detailed on this link. Do I need this connectivity in order to connect the ELM327 so that it can connect to the DME?

[Ch4ni]

I have been reading a few forums all these are saying the that ELM327 adapter will not work older BMWs as these are not ODBII and run BMW proprietary protocol. Smartphone connects to ELM327 adapter, but it runs endlessly through protocol searching and can’t connect to ECU

Has anyone successful able to connect to M52 with an Bluetooth adapter and sw app, if so could you please provide the details of the setup that works.

[Brianmoooore]

I use mine regularly with a M52Tu ( M52B28) .Car has both the OBD socket and the 20 pin round one.

[Ch4ni]

Looks like then your DME is able to support ODBII, On my engine loom I only have the 20pin round plug and dont think that is able to work with ODBII adapters only with BMW SW linke the BMW 1.4 scanner.

[Brianmoooore]

When I've connected 'ordinary' diagnostic equipment to BMWs that only have the round socket, I've had to use a converter lead that incorporates some electronics called ADS. I think it's essentially a level shifter.
Google ADS/OBD.

[DanThe]

Ive used an elm on my 1997 540i without problems, the car didnt have an OBD2 socket until I fitted one although ive never tried it with an adaptor cable

[Ch4ni]

Ive used an elm on my 1997 540i without problems, the car didnt have an OBD2 socket until I fitted one although ive never tried it with an adaptor cable

I would to fit ab OBD2 socket would you be able to share how this is done what connection are needed from the 20Pin to 16 OBD2 socket please

[DanThe]

I just used Earth, Ignition and the K-line White/Violet, no reason why the adaptor shouldn't work TBH

[Ch4ni]

After failing to get the Bluetooth adapter to connect, I used the iCarsoft Scanner i910 to read the engine codes and this time I get the following codes;
1) D9 CAN - BUs: NO EGS Transmission - this I take is not able to read the Auto Transmission module is there any way to clear this code for good?
2) 37 output stage for oxygen-sensor heater. sensor 2 (cylinders 4-6) does this indicate the lambda sensor for cylinders 4 to 6 needs replacing? Does this have anything to do with the Oxygen sensor relay which is not there anymore as the engine is now in the E30?

What symptoms would I get with this fault code with the engine running? What do I need to do to fix this fault?

[Brianmoooore]

If your M52 is running without the O2 heater relay, then I'm not surprised that you get the fault code. Solution - Fit the relay.
The O2 heater is used to bring the sensor up to temp. from cold, and occasionally to keep it there when the engine is at idle or not under load. Under normal running conditions, i.e. when driving along the sensor should stay hot enough from the exhaust heat alone.
Clear the codes, fit the relay, and test again.

[Ch4ni]

What is the wiring that I need to do to fit the relay can anyone share what I need to do to fit this relay what are the connections I need to install?

[Brianmoooore]

The socket should be on the M52 engine loom. Three relays in a row, just like on the old M20 or M40 loom.
http://www.autolib.diakom.ru/CAR/BMW/19 ... S/2431.pdf and http://www.autolib.diakom.ru/CAR/BMW/19 ... S/2432.pdf

[DanThe]

Only 2 relays needed on an M52, the lambdas take their power from the main relay same as everything else on the loom with a Red/White wire
The 2nd relay is for the fuel pump

That fault will just mean the heater circuit of the lambda is open circuit, so needs replacing, unless the loom is damaged of course

[Ch4ni]

Yes I have 2 relays on the loom, the loom was damaged I did repair it i might need to look at this again. To check this is the case I will swap the the lambda sensor with the other one and see if the fault follows it. If it does then it's the loom I need to look at.

[Brianmoooore]

Only 2 relays needed on an M52, the lambdas take their power from the main relay same as everything else on the loom with a Red/White wire

Really should look at the links I post, because there's clearly no relay for the lambdas! Never noticed that before.
Any idea why some of the red/white is shown dotted in the diagrams, Dan? Just for clarity, because it crosses so many other wires?

[DanThe]

I expect it is because it is all optional emissions related equipment, depending on market etc, you don't get that on UK E36's

[DanThe]

To check this is the case I will swap the the lambda sensor with the other one and see if the fault follows it. If it does then it's the loom I need to look at.

Just change the plugs around