E92 m3 whole Bank 1 instant misfire immediately after start

[john_s]

Hi folks, I got a misfire that's super difficult to diagnose. It's a 2008 e92 m3, completely stock, daily driver, 130k miles. A month ago when I drove back from work, when I came to a red light, it suddenly went into limp mode. I was 2 minutes away from home, so I drove it slowly to home. Note that this is exactly one day after the dealer did the positive battery cable recall.

Here is the symptom: immediately (~2 second) after the car starts, it went into limp mode, and throws cylinder 1,2,3 misfire code, and the general "multiple misfire" code. No other code ever. Just pure misfire of almost one bank. It throws these code 100% of the time, consistently immediately after the start. Both exhaust have unburnt fuel, I can see thin white smoke and smell the heavy fuel smell. If I went under the car after it limps for 1 minute, only driver side exhaust is hot. The passenger side (bank 1) exhaust is completely cold.

I have done days of research and have now replaced ALL 4 O2 sensors (2 pre cat 2 post cat), Both exhaust gaskets, fuel tank breather valve, spark plugs, and fuel injectors. The coil packs are not the problem, I swapped them around the misfire didn't follow, and I did a spark plug test with those coils and I can see sparks firing correctly. ISTA+ also confirms all spark plugs firing intervals are fine. In ISTA+ I can see cylinders 1,2,3,4 are completely dead, have 0 combustion. When I start the engine, cylinders 1,2,3,4 have combustion, but then very quickly died. I have also confirmed both the old and new fuel injectors are working by pulling them out and squirt on towels.

I'm starting to lose my sanity now. I'm thinking idle control valve, but the ICV feeds air to both banks simultaneously, why only bank 1 misfires? I remember reading somewhere that if the ICV fails, the throttle actuator takes over at idle, the engine doesn't misfire, it just idles higher. Throttle actuator has been replaced and is working fine.

Or did the dealer screwed up something electrical? If that's the case I should get the error immediately at the dealer lot, but not one day after 50 miles of commute.

Is there anything else on the S65 engine that is one-bank only? Vanos? Timing related?

Any help appreciated, thanks!

[spammysammich]

Check the grounds on bank 1?

[fs34]

Originally Posted by spammysammich

Check the grounds on bank 1?

I thought I was “check your grounds” guy, lol. The ignition grounds are integrated with the bolts/nuts for the wiring harness that sits in the valley. If you’ve replaced that much stuff, it could be the culprit. Take off the intake and make sure that the harness is bolted down. There are 3 nuts, one right behind the thermostat assembly, the other 2 around the back towards driver side. Ultimately cost me a bunch to find out that the previous owner had TAs replaced and the damn mechanic that did it did not put those nuts back into place.

[Ajolives]

Out of left field but maybe take the plenum off and start it up. Insta+ is confiming spark, couldn’t help to get a visual on the fuel and ITBs operating the way they should + checking out the grounds and such. Really odd problem…

[john_s]

Thanks for the reply, I checked the bank 1 side, is this the ground wires? I also checked that big braided ground wire under the car, it's pretty tight and not corroded.



Are these 4 nuts the ones that ground the wiring harness? Two are right behind the thermostat, two one both sides of the secondary air pump. They are as tight as a 10mm nut can be






I did took the plenum off, and with the car off, if I step on gas, all ITB open and close together and looks consistent.

[john_s]

Just swapped camshaft position sensors around, no use. Also just confirmed in ISTA that during startup all fuel injectors are working (9-12ms), immediately after startup the DME figured that something is seriously wrong with bank 1, and cut off cylinders 1,2,3,4, and ISTA shows fuel injectors 1,2,3,4 as 0ms (not injecting fuel due to cutoff). The ground of the fuel system and the spark system must be intact.

It must be something very obvious, otherwise the DME can't figure out within 1 second that it needs to cutoff bank 1.

In ISTA's misfire diagnose steps, it did mention valve spring........ Is that what I should check next, really hope that's not the case

Let me do a compression test first

[john_s]

F**k me, cylinder 1 has zero compression. Just in case my compression test kit is faulty (OTC 5605), I tested cylinder 2,3 and 5, with 2 and 3 having 180 psi and 5 has 150 psi. It's probably lower than ideal (not tested with wide open throttle, just disabled fuel system and cranking with foot on brake) but at least they have compression..

So most likely it's a stuck open valve right? Is S65 an interference engine? Am I completely f**ked?

[DanMpower]

Originally Posted by john_s

F**k me, cylinder 1 has zero compression. Just in case my compression test kit is faulty (OTC 5605), I tested cylinder 2,3 and 5, with 2 and 3 having 180 psi and 5 has 150 psi. It's probably lower than ideal (not tested with wide open throttle, just disabled fuel system and cranking with foot on brake) but at least they have compression..

So most likely it's a stuck open valve right? Is S65 an interference engine? Am I completely f**ked?

Possibly a broken valve spring? Doesn't really explain why a whole bank of cylinders is down though...

[spammysammich]

Do you have access to a bore scope? I picked one up on amazon that has two camera modes; straight on and periscopic view to let you look sideways in the cylinder.
Pull a little bit of your oil to see if there is forbidden glitter. Hopefully you got lucky and a valve got stuck and hasn’t caused more damage. Valve springs always linger in the back of my mind. Good luck.

[john_s]

Here is a short write-up for people with similar issues, hope google search brings this to you.

It is a broken valve spring. The spring snapped into multiple pieces, and the valve was in free fall. The remainder of the spring made sure the valve didn't fall all the way into the cylinder, which is what saved the engine. There was no piston damage, and the valve was straight, and compression was good after replacing the valve spring. I'm back to daily driving this m3 again.

I did the valve spring replacement myself. On a scale of 1 (adding windshield washer fluid) to 10 (engine rebuild), this job is about a 7. A few things I learnt:
1. Install ista. Follow its procedure. Never start this job just by watching a few videos or reading some guides. Just follow ista.
2. The aftermarket timing tool sold on FCPEuro is pretty good, the fitment is fine. Not all 3 screws can be attached to the head when the tool is set in place with engine at TDC, but that doesn't affect it's precision.
3. When you turn the harmonic balancer and the timing tool can be inserted to lock the crank, that doesn't mean the engine is at TDC. It could also mean that the engine is at one full turn after TDC. Always check the camshaft markings to make sure when the crank is locked, it is at the desired position (TDC, or one turn after TDC). ISTA tells you clearly what position the engine needs to be in, when you are adjusting timing, or checking timing, for each bank.
4. The valve spring installation is not that trivial. I used Lisle 36050, but it's not very good for this. I'm not strong enough to compress the spring enough to install the retainer, and in the process of doing that I scored the super smooth guide that the cam follower sits in. It's probably no big deal and it can be done with Lisle 36050, you just need to be strong. Or get a better tool.
5. Remember to change the valve stem seal as well. Mine was broken as well, probably by the broken spring.

[DrFerry]

Originally Posted by john_s

Here is a short write-up for people with similar issues, hope google search brings this to you.

It is a broken valve spring. The spring snapped into multiple pieces, and the valve was in free fall. The remainder of the spring made sure the valve didn't fall all the way into the cylinder, which is what saved the engine. There was no piston damage, and the valve was straight, and compression was good after replacing the valve spring. I'm back to daily driving this m3 again.

I did the valve spring replacement myself. On a scale of 1 (adding windshield washer fluid) to 10 (engine rebuild), this job is about a 6. A few things I learnt:
1. Install ista. Follow its procedure. Never start this job just by watching a few videos or reading some guides. Just follow ista.
2. The aftermarket timing tool sold on FCPEuro is pretty good, the fitment is fine. Not all 3 screws can be attached to the head when the tool is set in place with engine at TDC, but that doesn't affect it's precision.
3. When you turn the harmonic balancer and the timing tool can be inserted to lock the crank, that doesn't mean the engine is at TDC. It could also mean that the engine is at one full turn after TDC. Always check the camshaft markings to make sure when the crank is locked, it is at the desired position (TDC, or one turn after TDC). ISTA tells you clearly what position the engine needs to be in, when you are adjusting timing, or checking timing, for each bank.
4. The valve spring installation is not that trivial. I used Lisle 36050, but it's not very good for this. I'm not strong enough to compress the spring enough to install the retainer, and in the process of doing that I scored the super smooth guide that the cam follower sits in. It's probably no big deal and it can be done with Lisle 36050, you just need to be strong. Or get a better tool.
5. Remember to change the valve stem seal as well. Mine was broken as well, probably by the broken spring.

Well done doing all of that yourself and thanks for the write up. I have to ask though.. how the heck did you get the broken valve spring out of the head? Surely you had to remove the camshaft, and timing chains as well as other parts?

[Brandoch]

I really hope this isn't the next big thing to be popping up.

[spammysammich]

Originally Posted by Brandoch

I really hope this isn't the next big thing to be popping up.

Valve springs have always been a low percentage Achilles heel of this engine. Posts are few and far between but they exist.

[john_s]

Originally Posted by DrFerry

Well done doing all of that yourself and thanks for the write up. I have to ask though.. how the heck did you get the broken valve spring out of the head? Surely you had to remove the camshaft, and timing chains as well as other parts?

Yes, it's a whole timing job. Remove valve cover, drain coolant, remove front radiator fan and a bunch of coolant hoses, remove both driving belts and stuff in the way to get to the harmonic balancer. Check timing by turning the crank (I bought this to turn the crank) to TDC (or maybe one full turn after TDC) and lock camshafts with the timing tool. Loosen cam bolt, remove vanos gears (remember to lock the two exhaust gears with the timing tool), remove cam caps and camshafts, and you have access to the valve spring. I got lucky it's cylinder 1 that needs repair. It's going to be a lot harder if it's cylinder 4

[Tragiclil]

Is there anything we can do to prevent this? Preventative maintenance? Or is it just luck of the draw and hope this never happens?

[Redd]

Originally Posted by Tragiclil

Is there anything we can do to prevent this? Preventative maintenance? Or is it just luck of the draw and hope this never happens?

Not frequent enough occurrence to worry about it. Just drive the car.

[fs34]

This is how you follow up! Thank you and glad you are back up and running. When I went through a grounding issue I was quoted $7500 by the dealer for a valve spring replacement on 7. This is what we thought happened but it ended up being a missing nut on the wiring harness.

[nick3753]

About a 6/10 eh…… kidding, sort of. Nice work. Glad your back on the road.

[john_s]

Ah that's a typo, didn't notice I wrote a 6. I think it's about a 7 since it's not engine out, and you don't need to take the head off.

[m3cole]

Having this same issue with my car. Suddenly went into limp mode. I had it towed to North Raleigh Performance in NC where I also work. Went though full ista test plan and said the IAC was faulty, I replaced this last night and turned the car on and same issue. Also went through ista test plan on throttle actuators and they were but swapped them bank to bank just to see if may something changed. Cylinder misfire for bank one entire bank. Car will turn and and is fine for half a second and goes back into reduced power mode. Swapped actuators, O2 sensors, and checked injector pulsing and everything checks out. Going to compression test at the end of the day and see if we can find anything. This car really tests my patience lol

[tdott]

Different root cause, but similiar symptoums on a car I was troubleshooting.
Details here:
https://www.m3post.com/forums/showthread.php?t=2067525

[m3cole]

Originally Posted by m3cole

Having this same issue with my car. Suddenly went into limp mode. I had it towed to North Raleigh Performance in NC where I also work. Went though full ista test plan and said the IAC was faulty, I replaced this last night and turned the car on and same issue. Also went through ista test plan on throttle actuators and they were but swapped them bank to bank just to see if may something changed. Cylinder misfire for bank one entire bank. Car will turn and and is fine for half a second and goes back into reduced power mode. Swapped actuators, O2 sensors, and checked injector pulsing and everything checks out. Going to compression test at the end of the day and see if we can find anything. This car really tests my patience lol

Quick update. Compression test showed zero compression in cylinder 6. Broken valve spring is the culprit. Just have to see if the valve is bent or if we can get away with putting a spring in and calling it a day.