[tokenize]

Hello there.

I'm currently experiencing an issue on my BMW E90 320i with the N46 engine which is leading me into desperation. I've tried and replaced everything I could think of but I still get the issue and I'm hoping anyone might be able to help.

So the car was burning oil in the combustion chamber and I decided to remove the cylinder head in order to replace the valve stem seals. Since I was on it, I took the chance to replace the timing chain kit as well. The procedure went really well and after putting everything together the car was running great and I was pretty pleased with the results. Never had the car running so smooth. However, I started to notice that, when I start the engine after it has warmed to operating temperature, most of the time it struggles a lot to start. Eventually it starts and it runs as if nothing happened from there. If I stop the engine and start it again immediately it starts without any problem. The issue only happens after the engine has been stopped for more than 10 minutes or so. Cold starts have no issue at all.


In an effort to solve the issue I've already done the following (all new parts are OEM):
- New battery
- New starter motor (old one was very worn and I replaced it before this issue anyway even though it worked fine)
- New crankshaft positioning sensor
- New camshaft positioning sensors
- New MAF sensor
- New engine temperature sensors (both thermostat and engine block)
- New fuel pressure regulator and fuel pump
- Cleaned the fuel injectors in a specialized fuel injection company
- Rechecked engine timing like 5 times to ensure I did everything right, but it always comes as 100% correct

Nothing has fixed the problem so far or had an effect on the problem at all. I'm really stunned by this. The car runs perfectly fine besides this issue. I have no DME error codes, the car has normal power and runs smooth as ever. I really have no clue what could cause the issue.

Thank you in advance for any help.

Best

[TriumphTim]

Maybe check the ground strap?

[tokenize]

Thanks for the answer. I checked and it's fine, can't find anything wrong with it.

[michaelalex17]

If the starter has been changed and battery has been changed I'm going to go with a bad ground as well

[tokenize]

I've rechecked all electrical connections from the starter, battery and engine compartment and I can't find anything wrong.

Also, if it really is a bad ground connection, why would it only happen when the engine is hot and eventually the engine just starts? I don't feel the starter motor struggling, it's running at full speed as far as I can tell.

[Tambohamilton]

Use inpa to look at shadow codes.

Have you looked in the DME box? Not that I have anything to go by, I'm suspecting a DME issue.

[tokenize]

What exactly are shadow codes? Never heard of it.

I've rechecked all wiring connections coming out of the DME box and couldn't find any issue. When you say that you suspect a DME issue are you refering to wiring or the DME itself? I can't find anything wrong on INPA or ISTA.

[TriumphTim]

This problem started after removing the head?

I would check the wiring to the temp sensors. I would make sure all sensors are reading at hot temps correctly.

[tokenize]

Originally Posted by TriumphTim

This problem started after removing the head?

I would check the wiring to the temp sensors. I would make sure all sensors are reading at hot temps correctly.

Yes, that's right.

As far as I'm aware, there are 3 temperature sensors in this engine in the following locations: thermostat, engine block and at the radiator outlet. In INPA I can see the readings for the thermostat and radiator and it seems they're fine. Regarding the engine block temperature sensor, I cannot be sure it's working as I cannot read it's value anywhere, so I replaced the sensor. In any case, I will again recheck the wiring for all of them.

[Tambohamilton]

Originally Posted by tokenize

What exactly are shadow codes? Never heard of it.

I've rechecked all wiring connections coming out of the DME box and couldn't find any issue. When you say that you suspect a DME issue are you refering to wiring or the DME itself? I can't find anything wrong on INPA or ISTA.

I think INPA refers to it as 'Information Memory' (IM). They're errors which have been logged but haven't occurred regularly enough to qualify as persistent errors and be logged in error memory.

I'm thinking the DME itself. But like the next poster says, it would be strange that it would manifest itself directly after head work. Scrolling through live data might be useful too.

[bluewater328]

Originally Posted by tokenize

Hello there.

I'm currently experiencing an issue on my BMW E90 320i with the N46 engine which is leading me into desperation. I've tried and replaced everything I could think of but I still get the issue and I'm hoping anyone might be able to help.

So the car was burning oil in the combustion chamber and I decided to remove the cylinder head in order to replace the valve stem seals. Since I was on it, I took the chance to replace the timing chain kit as well. The procedure went really well and after putting everything together the car was running great and I was pretty pleased with the results. Never had the car running so smooth. However, I started to notice that, when I start the engine after it has warmed to operating temperature, most of the time it struggles a lot to start. Eventually it starts and it runs as if nothing happened from there. If I stop the engine and start it again immediately it starts without any problem. The issue only happens after the engine has been stopped for more than 10 minutes or so. Cold starts have no issue at all.


In an effort to solve the issue I've already done the following (all new parts are OEM):
- New battery
- New starter motor (old one was very worn and I replaced it before this issue anyway even though it worked fine)
- New crankshaft positioning sensor
- New camshaft positioning sensors
- New MAF sensor
- New engine temperature sensors (both thermostat and engine block)
- New fuel pressure regulator and fuel pump
- Cleaned the fuel injectors in a specialized fuel injection company
- Rechecked engine timing like 5 times to ensure I did everything right, but it always comes as 100% correct

Nothing has fixed the problem so far or had an effect on the problem at all. I'm really stunned by this. The car runs perfectly fine besides this issue. I have no DME error codes, the car has normal power and runs smooth as ever. I really have no clue what could cause the issue.

Thank you in advance for any help.

Best

You seriously went through all the steps I'd go through minus the ground strap (Which you just checked). Injectors would have been my guess.

You're getting to the point where its bad stuff left. Manual or Auto?

[tokenize]

I will perform a leak test on the injectors when I can. It's a manual.

[tokenize]

It's with a mix of happiness and shame that I found out the issue for this mystery...

It's the injectors. One of them has a leak when the system is pressurized which floods the intake for that cylinder and explains all the symptoms. I never even considered this because they were cleaned and tested in a specialized injection company. But it turns out at least one of them is defective. I've returned them to the company for further tests but its unlikely the leakage can be fixed and I'll end up having to buy 4 new injectors.

This is another clear case that throwing parts at a problem does nothing but spending unnecessary money... But well, I'm happy the mystery is solved anyway. Thanks for all the help.

Cheers

[Tambohamilton]

Glad you found it, well done!