Radiator busted, now misfires on cylinders 5 & 4

[Masospaghetti]

Originally Posted by jac

I was able to run the cylinder compression test while the engine was at operating temperature:

Cylinders 1, 2, 4, 5: 160
Cylinders 3 and 6: 170

Those are decent readings, right?

Also, thank you @TryX5 and @Henn28 for the advice on cleaning/drying out the harnesses near the driver side of the radiator. I cleaned/dried that big plug going into the ABS unit and that seems to have cleared a few errors!

The mysfire is still on cylinder #5. But what is interesting is that the mysfire only shows up after I try to drive a bit aggressive. If I drive it without any hard acceleration it doesn't seem to occur.

What should I look at next to figure this out?

Those numbers look fine for compression. if it's only one cylinder and compression is good, the only other thing specific to that cylinder is the fuel injector, although I don't know why it would have crapped out from a busted radiator. You could try swapping injectors between two cylinders to rule it out. It's fairly easy to do - the most annoying part is getting the electrical connectors off of the injectors, and you'll want to have replacement o-rings on hand. You could also try BMW Logger and record a drive session to get a bit more data.

[jac]

Thank you all. I did measure the resistance on the 6 injectors:

Injectors 1, 5, 6: 11.8 ohms
Injectors 2, 3, 4: 11.7 ohms

I just swapped injectors 2 & 5. Going for a ride.

The compression test was 6 strokes. I have not put in new spark plugs, but have swapped the spark plugs and the coil positions and that did not change a thing.

Yes, I got a cooling system pressure tester kit a few weeks back. I have not used it yet. Gonna do that, anything I should look out/do for that?

[80stech]

Any updates ? The idea behind the cooling system pressure tester would be to check for a head gasket/crack issue.

[jac]

I cleared all the codes and adaptations using INPA, and left the car running in the driveway for like 45 minutes.

I was in the car for those 45 minutes, trying to find out how to log RPM, throttle angle, lambda trims, cylinder roughness, and VANOS on INPA, but I did not find anything. :-(

While I was sitting there, I noticed the following:

- The engine turns on without any issues
- The yellow trifecta is ON (Triangle, ABS, Brake)
- I turned the steering wheel all the way left and right several times, but no effect on the trifecta. This also started happening after the radiator issue, and I noticed that the lights usually change to yellow Triangle and ABS, but red Brake warning light, after driving.
- While it warms up, the engine sits at around 750 RPMs
- As the car is warming up, the engine stutters every few seconds. The RPMs go down briefly to almost 500, and then the engine quickly normalizes back up to 750. It does this until the temp needle reaches the top half of the blue marker in that gauge.
- After the gauge moves past the blue zone, the engine purrs like a baby. It is super smooth.
- It sat there for 45 minutes (while I looked through all the INPA screens) completely steady. At this idle, it sits around 700 RPMs.
- It did not throw any codes while it sat there idling.

I have not driven it yet as I have been busy at work and am still figuring out what to use to log that stuff I listed above. Someone recommended a software called TrustO, but the laptop I use for the car is too old (WinxP), so I gotta figure that out.

[80stech]

There should be codes if there is a trifecta. I wouldn't be too worried about logging stuff. Drive the car to get the misfire and then DME will actually log conditions (INPA codes detail section) when code sets, but I doubt that is going to help you very much.

[X5chemist]

The trifecta will appear if battery voltage gets too low or battery is disconnected. As suggested, drive it for a bit until codes appear.

[80stech]

Yeah, I just re-read some of this and the OP already has a cooling system pressure tester, I thought it was ordered but must have been a different thread, so should be using that to verify the head gasket or crack instead of trying everything to pretend that it isn't. Also confusing is that INPA is talked about and screen shot is ICarly or something ?? Anyway, OP let the car sit overnight with pressure on the cooling system and plugs out then crank in the morning and watch if coolant comes out of one of the spark plug holes.

Side note-- Any time you swap around parts looking for a misfire, especially when the DME has cut fuel, you should at least clear the codes to get the DME to retry the cylinder you are looking at or it might stay shut down and totally confuse the situation.