X5 35D misfire help!! (Solved)

[RL18]

Originally Posted by Colbyt93

So update, I've read a while ago about fuel getting into the dde from a leaky sensor so I figured I'd check and sure enough as soon as I open the box the dde sits in, reaked of diesel, so I took the computer out and it was fairly saturated as well as the harness. I cleaned everything thoroughly with electrical cleaner and a light scrubbing with super soft brush, as well as cleaned up the wire harness/connectors the best I could, then started to search for a leaky sensor and sure enough the fuel temp sensor just before the hpfp was soaked inside the plug, so with that on its way and the dde all dried/installed I'll give an update once the new fuel temp sensor is installed, hoping this is the cause of my mystery misfire!

Damn I hope the dde is okay. I haven’t had that issue yet but I guess I should look into it too. I’ve already had my dde box flooded out and fried once. Thank god I had a spare dde at the time.

[Colbyt93]

So I cleaned out the dde, let it dry and reinstalled as well as a new fuel temp sensor/fuel line that was leaking fuel into the harness and have zero change in running, zero misfires until it's been at running temp for 10-15 min, then it starts to miss 🙄 so at this point I'm not sure what to even look for

[wcs531]

Originally Posted by Colbyt93

So I cleaned out the dde, let it dry and reinstalled as well as a new fuel temp sensor/fuel line that was leaking fuel into the harness and have zero change in running, zero misfires until it's been at running temp for 10-15 min, then it starts to miss �� so at this point I'm not sure what to even look for

DDE could be damaged, I'd get a spare and send to your tuner. Still strange its temp dependent though

[Colbyt93]

I did contact Kassel performance about cloning my dde but that's going to run me just over 1k and I'd hate to do that and it not be the issue so I might bring it down to them anyways to run diagnostics or find somewhere near me than can look further into it, it seems like once the x5 goes into "closed loop" is when it starts to act up

[Colbyt93]

Well I found the problem everyone, cylinder 4 has left the chat 😥

[wcs531]

Originally Posted by Colbyt93

Well I found the problem everyone, cylinder 4 has left the chat ��

Holy...so that is the cylinder wall? How does it fail in a square chunk like that, very bizarre

[Colbyt93]

I have no idea, and there was oil seaping down on the one side, it's more amazing that it still runs/drives perfect, just smokes at idle once at running temp

[wcs531]

Any strange/awful noises?

[Colbyt93]

Not a single out of place noise, little puff of smoke at start up which is normal on deleted diesels, not an ounce from then up till running temp, then slowly gets worse the longer it idles, doesn't drink any oil and drives on highway like a dream 😂 I already have a new engine lined up so basically going to "build" it, new gaskets/timing chain/ ECT and swap it out one weekend

[wcs531]

That is absolutely crazy and kind of scary that it wont really show major issues when it seems like its on the edge of catastrophic failure. Do you check your filters when you do oil changes? I would be interested to see how much stuff is in it.

My engine makes an audible tick when cold (engine cold and around freezing or lower out) but fine once warm and doesnt seem to do it in warmer weather. I have a pending code for misfire on cyl 3 so hoping its just an out of spec injector that doesnt like the cold weather/more viscous diesel.

[jbash87]

what side of the cylinder is that? Is it a wall shared with another cylinder?
Almost looks like a weld repair, but it sounds crazy that someone would attempt that.
I can't imagine the piston rings would play nice with that surface either.

Will you be tearing the engine down once removed?

[Colbyt93]

Originally Posted by wcs531

That is absolutely crazy and kind of scary that it wont really show major issues when it seems like its on the edge of catastrophic failure. Do you check your filters when you do oil changes? I would be interested to see how much stuff is in it.

My engine makes an audible tick when cold (engine cold and around freezing or lower out) but fine once warm and doesnt seem to do it in warmer weather. I have a pending code for misfire on cyl 3 so hoping its just an out of spec injector that doesnt like the cold weather/more viscous diesel.

I always cut the filters open and checked and there was never any signs of metal or anything odd, both of my m57s have a slight tick when it's below freezing but it goes away fairly quickly, never really struck me as odd, my old TDI Jettas made all kinds of racket when they were cold, I would get the injector checked out ASAP, from what I was reading an injector that's going bad and spraying too much fuel can be part of the cylinder cracking issue. I'm not sure if that's 100% true but I guess it's a possibility

[Colbyt93]

Originally Posted by jbash87

what side of the cylinder is that? Is it a wall shared with another cylinder?
Almost looks like a weld repair, but it sounds crazy that someone would attempt that.
I can't imagine the piston rings would play nice with that surface either.

Will you be tearing the engine down once removed?

It is the shared wall side with cylinder 3, I was going to throw the borescope into cylinder 3 and take a look at it but decided I didn't feel like doing it since I've already discovered my issue lol, And I don't believe it was a weld repair, upon service records from the previous owner the only real maintenance other than oil change and being deleted is injector 6 had to be replaced as well as the small turbo, I will be tearing the engine down once I get everything swapped because I'm very curious myself, You can't see it in the picture but it also looks like the edge of the piston may be melted also 😂. The scary part is I've been using this to commute to work and back an hour and a half each way and it drives totally fine just smokes it idle 😂😂

[wcs531]

Originally Posted by Colbyt93

I always cut the filters open and checked and there was never any signs of metal or anything odd, both of my m57s have a slight tick when it's below freezing but it goes away fairly quickly, never really struck me as odd, my old TDI Jettas made all kinds of racket when they were cold, I would get the injector checked out ASAP, from what I was reading an injector that's going bad and spraying too much fuel can be part of the cylinder cracking issue. I'm not sure if that's 100% true but I guess it's a possibility

Yikes, thanks for the heads up. I will probably just order a new one instead of dealing with testing/down time.