[QA51M]

Good day everybody. This is my first post. I hope to get some advice and direction towards fixing my engine misfire. I have a 2008 325i M sport with the 3 litre n53b30 218hp engine mated to 6 speed manual. I bought the car off my older brother (with a lovely family discount) in February 2019. He's had the injector recall in 2011 done and also the hpfp recall. He was very aware of all the weaknesses in the n53 so was very careful about treating her gently when required. Keeping revs below 3k until oil temps are at 90, careful gear shifts, regular servicing, oem parts only ever used, good fuel. All that good stuff.

By April 2019 I developed a misfire after using a very questionable petrol station that was far too cheap to be true. There may not be a link or they may Im honestly not sure. So I decided to do my first DIY and changed all 6 coils with the correct bosch coil packs. I did intend to change plugs but I made the rookie error of not purchasing the angled socket wrench so the plugs stayed in there. Changing the coil pack fully resolved my problems. No misfire, cold start was so much better, full power, fuel mpg decent enough.

So no real problems for 14 months until june 2020. My car developed a misifre again. Engine light appeared on my dash. Idle revs bouncing from 400 to 900 rpm. Very rough running engine. Severely reduced power and stuttering. Initially shutting the engine off and on would clear the engine light and misfire but revving beyond 5k rpm would cause misfire to return. That lasted for a few days and now the misfire is pretty much constant with engine light. I changed the spark plugs finally but the problem still persists.

I have ran codes with my in laws obd scanner which show cylinder 3 misfire. I suspect either injector is leaking and needs replacing or while i changed the spark plugs i have caused a poor connection to the coils. The reason being I noticed the valve cover gasket is leaking (common with the n53) and there is oil in the spark plug wells and its covering the coil pack boots.

Im planning on cleaning out all the oil in the spark plug wells and cleaning the coil packs of oil, applying beru zf01 grease to the inside of coil pack boots and seeing if a clean connection between coils and sparks resolves the issues.

Does anyone have any pearls of wisdom they'd like to share. I am trying to avoid spending the hundreds involved with replacing injectors. As we are recovering from lockdown during which I was furloughed for 3 months money isnt in great abundance right now. I definitely would appreciate your help however big or small

[4foothill]

This thread is the best diagnostic tool we have for the n53: https://www.e90post.com/forums/showthread.php?t=1525311

Also are you sure it's the VCG and not the oil filter housing gasket?

[QA51M]

Thanks for the fast reply. That is a mega thread! Yeh my oil filter housing looks pretty decent but the area where the vcg is and around the bolts is black with oil. After reading that its got me thinking maybe my pcv is having issues. As my symptoms seem to fit the bill.

[QA51M]

Update for whoever comes across this issue. I noticed that there was oil on the top of my coils and on the inside of my engine cover. My valve cover is leaking but not that much as to cause the oil to spread upwards like that. Turns out the source of this oil leak is my oil filler cap! The part is £18 from bmw directly. Such a simple problem yet that oil was affecting the coil pack and caused the coil in cylinder 3 to fail and misfire. I confirmed this by checking and clearing codes then swapping the coil with cylinder 1 and obviously the codes followed the coil! Ive ordered a replacement and while my engine cover was off i cleaned all the ignition wire connections with electrical cleaner and compressed air, cleaned oil from the spark plug wells which there wasnt really that much, which proves my valve cover gasket isnt all that bad yet. Hope to post the good news after i plug in my new coil.

[QA51M]

Shocking update. Replacing the coil has not resolved my misfire. Cylinder 3 misfire code followed the coil when i mvoed it to cylinder 1. But after replacing the coil today and clearing codes i still have a misfire on cylinder 3. The only thing left now is the injector. But im still completely confused as to why the misfire went to cylinder 1 after moving the coil. Unless i had a bad coil and also a bad injector at the same time. But to be fair the car is a lot better after changing the coil but as soon as i rev beyond 3000rpm the eml comes on and misfire appears. Clearing the code instantly resolves it. Looks like im going to have to spend some money on another index 11.

[ctuna]

Maybe you need a Walnut Blast to clean the Carbon off the Intake
Valves. Also we never got the N53 in the US.

Maybe this guy could help you
https://www.nathansbmwworkshop.com/b...or-dean-videos
He's in the UK

[E92William]

Lol^ dean he'll probably make you subscribe to his paid group where he'll actually answer your questions with what he thinks. If you're gonna pay might aswell take it to a mechanic for a proper diagnostic.

I had great luck on my n54 running injector cleaner a few times through the car specially with a tank of gas a bit low. Mostly got rid of the idle stumble though not completely but it did resolve the misfire at higher rpm and limp mode. But if you wanna go the new injector route is the best one.

[4foothill]

Originally Posted by QA51M

Shocking update. Replacing the coil has not resolved my misfire. Cylinder 3 misfire code followed the coil when i mvoed it to cylinder 1. But after replacing the coil today and clearing codes i still have a misfire on cylinder 3. The only thing left now is the injector. But im still completely confused as to why the misfire went to cylinder 1 after moving the coil. Unless i had a bad coil and also a bad injector at the same time. But to be fair the car is a lot better after changing the coil but as soon as i rev beyond 3000rpm the eml comes on and misfire appears. Clearing the code instantly resolves it. Looks like im going to have to spend some money on another index 11.

I would also try new plugs before getting new injectors. Leave your car overnight and then replace the plugs and smell them, if they smell of petrol then your injectors are gone.

[QA51M]

So i have a nice update on the car. After changing coils and sparks i took my car into BM tech in Manchester and they ran diagnostics which confirmed a faulty injector in cylinder 3. After replacing and coding the car is a peach. Cold start is great, idles smooth, great linear power band right the way to 7k, and maybe I've been out of the car for too long but im sure its faster 😅 regardless im very glad to have the engine running healthy. Now its time for some pads and discs and probably some shock absorbers too. Thanks for everyones replies! This has been my first thread after so many years browsing the forums as a guest user.

[QA51M]

2 years later the n53 is misfiring but cylinder 1 this time. There's a lot of oil around the valve cover gasket. Huge amount of thick sticky black oil in the spark plug well for cylinder 1. Coil pack boot all black with sticky oil.

HERE'S THE SHOCKING BIT the spark plug in cylinder 1 is wobbling around all loose. It doesnt come out with the coil pack which grips onto it pretty tight. But that spark is just rattling around when the coil is off.

Driving full throttle above 3k rpm triggers misfire and eml and code 29CD misfire cylinder 1. Clearing the code clears the eml and engine runs smooth again until you floor it and go past 3k. So the cars happy with normal speeds and steady acceleration. But any spirited driving upsets her.

Im going to see if i can remove the spark once i get the correct tools. Just hoping its not broken thread on the head or a broken aluminium bolt on the head.

[Y.dae]

Originally Posted by QA51M

So i have a nice update on the car. After changing coils and sparks i took my car into BM tech in Manchester and they ran diagnostics which confirmed a faulty injector in cylinder 3. After replacing and coding the car is a peach. Cold start is great, idles smooth, great linear power band right the way to 7k, and maybe I've been out of the car for too long but im sure its faster 😅 regardless im very glad to have the engine running healthy. Now its time for some pads and discs and probably some shock absorbers too. Thanks for everyones replies! This has been my first thread after so many years browsing the forums as a guest user.

Hi mate, glad to hear you were able to get rid of the persistent cylinder 3 misfire a couple years ago. I’m currently having a similar issue with my N53. There seems to be oil leaking from the filler cap and into the cover. I have a persistent cylinder 2 misfire despite chaning the coils, spark plugs and the injector. I’m thinking of taking it to bmw. I just have a question if you don’t mind. Around how much did it cost to replace the injector with them? Cheers