[Had0uken!]

Hey guys,

Having a bit of an issue with my 2007 335i N54 MT. Was driving the car the other day around 2500-3000rpm the engine light came on, pulled over and scanned this with MHD and had a code for multiple cylinder misfires. Figured it was going to be fried Mosfets. Had to start the car to pull into a side road and wait for recovery. As i pulled onto the side road the car cut out. Whilst waiting scanned the car again and got a 30BA along with 3100 code confirming Mosfets gone.

When the recovery arrived i needed to move car forward a metre to get onto the truck - tried starting it and the car just cranked for 30 seconds, threw a half engine light and gave up.

Towed the car home and had all 6 mosfets swapped out. Thinking this was the end of that i plugged ECU back in and went to startup - same thing again, first time i tried to crank it the engine fired up for a second at 600rpm then slugged back down and died, then after that whenever i crank it rpm's stay around 1-300rpm and no start.

Scanned the car again and the mosfet code is now gone, i'm left with 2A9A camshaft intake sensor correlation and 3100 boost pressure code along with a shadow code for HPFP (assuming this is due to the failed starts). (reset all these codes and when i try to crank again these come back) Anyway i can hear the fuel pump priming and smell fuel when it's cranking so that kind of rules out HPFP to me (this is 2 years old - less than 20k on it).

I've swapped the vanos solenoids and camshaft sensors around to see if the code followed from intake to exhaust side - It didn't.

So that's as far as i've got. Any advice?

I've started pulling the cam cover off to check the chain condition and waiting on a timing tool kit to arrive to verify timing. Assuming if timing and compression test checks out it can't be an engine issue? The crank bolt seems tight and so do the vanos bolts (I can turn the engine by hand and observe all the valves going up and down)

Could it still be an ECU issue if the mosfets damaged anything else? and is there anyway to actually test the new mosfets are working - the 30ba code is gone but the multimeter test on the mosfets just seems to measure whether the mosfets are good or bad but not necessarily whether they are connected to the board properly?

[JuniorB]

Car needs fuel and spark so, if the plugs are fuel smelling, then is not igniting. Make sure you have correct pressure, this can be fuel related.Dont count on those codes yet until is running.. The car should run, check all ECU fuses.

[Had0uken!]

Oh okay! So I should ignore the codes for now as it should still run with them? Sparks will be out over the weekend to check them. I know theres the one fuse in the ECU box and assuming the rest will all be in the glovebox?

[Had0uken!]

Checked the fuse in the ecu box and all the ones in the glove box that relate to DDE, the engine symbol and the cog image. All checked out okay!

[JuniorB]

Cars pop up random shit for incomplete cycles, I didn't say ignore them, but until the car is running, hold off on replacing parts. The car will still run on misfires, but the engine just cranking leads to fuel or spark. You have to eliminate both. Are you getting spark, do you have good fuel pressure?

[Had0uken!]

Originally Posted by JuniorB

Cars pop up random shit for incomplete cycles, I didn't say ignore them, but until the car is running, hold off on replacing parts. The car will still run on misfires, but the engine just cranking leads to fuel or spark. You have to eliminate both. Are you getting spark, do you have good fuel pressure?

Originally Posted by JuniorB

Cars pop up random shit for incomplete cycles, I didn't say ignore them, but until the car is running, hold off on replacing parts. The car will still run on misfires, but the engine just cranking leads to fuel or spark. You have to eliminate both. Are you getting spark, do you have good fuel pressure?

Thanks for the advice!

Finally managed to get somewhere with this but I can only work on it on weekends so it's slow progress! You were right - Car wasn't getting spark - couldn't see why not as the mosfets had been replaced and no more codes for them. Turns out both camshaft were the equivalent of one tooth out so looks like the Timing slipped and engine was trying to protect itself by not starting. Hoping there wasn't any further damage (think it must have slipped when trying to crank the car to move it towards the tow truck) as before that no cam codes appeared and all was running fine (except 3 cylinders). Anyway retimed the engine and it started up straight away. Checked compression on all cylinders and they're all within 5psi of each other so everything else seems to check out.
Weird thing is when I got the engine running again I had to replace an ignition coil in cylinder 4 - even though it was bank 1 the mosfets went and I'm now getting a misfire on cylinder 6. I've swapped the plugs and coils over with another cylinder but the misfires still on cylinder 6 so thinking it could be the injector. Is it possible to swap out injector 6 with injector 5 to see if the misfire follows? I'll probably just buy 3x index 12 injectors for this bank anyway but I wanna make sure it is the injector before I order £500 of injectors. I know your not supposed to remove injectors as they have single use seals but it would only be run for a couple of minutes to determine if is a dodgy injector.

I'm also getting an extremely loud screech when the engine starts, I was thinking the starter motor but when I tried cranking the car with fuel pump and coils unplugged to test compression there was no squeal noise and the belt and starter will have been spinning then also. It only seems to happen after the engine has cranked to life and currently stops as soon as cylinder 6 misfires and the revs change (you can hear the revs jump up a few hundred rpm when cylinder 6 misfires during cold start then screech stops in the video!) so I'm thinking it's something to do with the misfire or it's the starter not disengaging? Cylinder 6 plug was covered in fuel when I pulled it after I recorded the video.
I'll post the video here. Any idea what it could be? Belts 3 months old and ac compressor is 3 months old and alternators about 12 months old.

[Had0uken!]

Thought I'd update this as I hate seeing a problem on the internet and no resolution! Issue was injector 6! Didn't even know injectors could squeal but I pulled it out and stuck a new one in and problem solved! No squeal and no misfire!!

[JuniorB]

Glad to see its up and running, it's best to exhaust a lot of options before throwing a ton of parts at it. There has been a few no starts, and a lot of codes that pop up that have nothing to do with each other. A bad fuel injector seal can blowby causing the whistle. It's running and ready to enjoy!

[Had0uken!]

Originally Posted by JuniorB

Glad to see its up and running, it's best to exhaust a lot of options before throwing a ton of parts at it. There has been a few no starts, and a lot of codes that pop up that have nothing to do with each other. A bad fuel injector seal can blowby causing the whistle. It's running and ready to enjoy!

I'm getting somewhere with it, just slow progress with work and the shorter days.

Not really had a chance to drive it until this weekend as it needed the annual MOT inspection which it passed (probably done 80 miles now since fixing it). Getting another issue now though - on the first cold start every morning it seems to throw a wobble. I'll go to crank it, engine will fire up sounding rough, theres a squeal again (nowhere near as loud as before) and it will run really rough for 10 seconds before it throws an engine light and shuts off. I can then immediately restart it after this and the car starts up perfectly. I scanned the code i'm getting and its coming up as 29F2 (HPFP code). I'm thinking it may not be the fuel pump though as it only does this on cold start for the first start of the day. As soon as it stumbles and shuts off i can restart it straight away and it's fine. I've already replaced one bank of injectors so thinking i could have a leaky injector on another bank maybe? or is it likely to be the HPFP? (current one is 2 years old - 30k miles).

Also i'm assuming this is related - when driving if say i let off at 3krpm and let the car coast down to 2k and then tap the throttle i hear a pop noise from the exhaust (not the usual burbles, more of a pop) and it also seems to do it when i'm cruising and put the clutch in to change gear and the revs drop. So thinking that would point to a leaky injector? and then when i touch the accelerator its burning off excess fuel?

I will get this stupid car running right! :|