Cylinder 6 misfire woes

[rf900rkw]

Okay. Fun Fact number 4(??) Many OBD2 codes are two trip. This means the first time the computer sees a problem, it flags it and sets a pending code. If it sees the same problem again in x drive cycles, then it sets the hard code and turns on the MIL. So your light on every other drive is normal.

Engine not really warm yet, but is in closed loop. VSS 0 MPH. Engine load 14% (idling), RPM at idle. You were sitting still when the code flagged. Further fuel trims for both banks are slightly negative. That isn't right, but it's detail. It does show there is no false air. No vacuum leak. No backwash in the exhaust.

So it certainly looks like a light misfire at idle. If you let it idle long enough, it will shut down that cylinder and run like crap. If you fire up and get into the revs, drive off, before much time it runs okay. With the parts testing and swapping you have done, I would be popping the manifold back off to inspect the turbulence jets.

[Z3J1]

I’m grateful this thanksgiving for Mr. Randy

If it sees the same problem again in x drive cycles, then it sets the hard code and turns on the MIL. So your light on every other drive is normal.

Makes sense and that does seem to be my pattern. Clear CEL… starts up and runs great… Shut down and cool down… starts up with CEL… repeat.

fuel trims for both banks are slightly negative. That isn't right

Can you explain what’s not right? My understanding has been generally trims within plus/minus 10% is normal.

So it certainly looks like a light misfire at idle… With the parts testing and swapping you have done, I would be popping the manifold back off to inspect the turbulence jets.

Thank you for the reassurance it is probably something minor. What are turbulence jets and what am I looking for?

However, before popping the manifold off again, I did a little shopping and may try putting on…
- the original coil,
- a new genuine NGK BKR6EQUP spark plug,
- and a refurbished genuine Siemens fuel injector.

Any chance cylinder 6 is a snob and doesn’t like to play with the aftermarket parts that are currently on there?

[rf900rkw]

Trims +/-10% may be normal for a Honda. This era BMW will code at +10 or -8. This engine when right when run at +3% on E10 fuel. So the -3 is 6 points away from normal. But it's equal both banks, do not the cause of the misfire.

The turbulence jets are at the end of the idle air passages in the head. The small hole next to each intake port is the idle air passage. As stated pages ago, at light throttle all air goes through that passage rather than the main intake ports. There is a 5mm hole at the end that can plug up and cause low speed misfires like this.

[BimmerBreaker]

He has stated a few times that while it presents more often on cylinder 6, it seems like there may also be codes for other cylinders... though they probably take longer to present, and since he keeps clearing the codes, may not get an opportunity to show up. As such I'd still fix the vacuum leak that was observed. But the fuel trims being way off on bank two does make it seem like there is a problem only affecting that bank

I should add the last time I checked my obd reader, it showed a pending trouble code for a cylinder 2 and 3 misfire.

Here is where the turbulence/secondary runner is located, as well as a little information on the system, they are the green runners in the diagram below which are only supplied by the ICV

[Z3J1]

Thank you Mr. Randy and BimmerBreaker for all that great info and guidance. I’ve decided to remove the intake manifold and check those turbulence jets. Given my symptoms, it does seem to make sense.

Since I’ve removed the intake before, it should go much faster and easier. But even before doing that, would it be worth a try to open the IACV somehow and blow compressed air in order to clear any blockage in the turbulence jets? Or maybe that’s a silly idea since it’s a sealed system? Just a thought.

[Z3ms52]

Are you suggesting you can plug a laptop into the car….what type of connector do you need and any special software?

[RedRedZ]

Are you suggesting you can plug a laptop into the car….what type of connector do you need and any special software?

https://www.bimmerforums.com/forum/s...xperimentation

[Z3J1]

Another freeze frame. I don’t think there’s much difference from the first freeze frame i posted earlier except bank 2 STFT was negative 3.1%, while the second freeze frame now has positive 3.1%. Does this continue to support the possibility of a blocked turbulence jet on cylinder 6?

[Z3J1]

Took me a mellow 1.5 hours to get the intake off again.

I blew into each of the small turbulence/secondary runners (think CPR!) and they all seem totally clear. So I think that theory is dead. What else can I check before putting the intake back on?

[Z3J1]

One other shot in the dark… the fuel injector rail mounts don’t really align with the threads on the intake. It gets worse going from front to back (cylinder 1 to 6). I have to push the rail towards the intake side (driver’s left) a few millimeters. It’s enough to cause the injectors to enter the intake less than perpendicular. There’s no leak but maybe the injector spray is oriented a bit off. Again, it’s more pronounced in cylinder 6. Original fuel rail and intake as far as I know.

Has this happened to others? Silly theory? I’m running out of options.

[Z3J1]

Another theory… valve cover gasket. Maybe I should’ve mentioned that way earlier! My less-than-professional smoke test did not indicate any leaks there but there’s definitely leaking along the lower rim of the cover. Spark plugs and tube are clean though. The leak seems pretty uniform across the cover, not noticeably more near cylinder 6.

I was going to replace the gasket later but maybe I should do it now?

[Z3J1]

One other shot in the dark… the fuel injector rail mounts don’t really align with the threads on the intake. It gets worse going from front to back (cylinder 1 to 6). I have to push the rail towards the intake side (driver’s left) a few millimeters. It’s enough to cause the injectors to enter the intake less than perpendicular. There’s no leak but maybe the injector spray is oriented a bit off. Again, it’s more pronounced in cylinder 6. Original fuel rail and intake as far as I know.

Has this happened to others? Silly theory? I’m running out of options.

More investigation. The part number on the side of the rail is 14330221353. Google isn’t helping much and I’m wondering if this is not intended for this engine.

When I look on realoem, the part number that shows up is 13531433024 https://www.realoem.com/bmw/enUS/par...&q=13531433024

Could someone confirm whether I have the correct rail?

[rf900rkw]

The turbulence jets are in the head, not the runners in the manifold. Did you check the head ports? Down near the intake valves.


The VC gasket is indeed a common source of vacuum leaks. Your negative fuel trims say that's not problem.

[Z3J1]

The turbulence jets are in the head, not the runners in the manifold. Did you check the head ports?

Cylinder 6 jet looks completely clear, as do the other jets.

[Z3J1]

If you look to the right of where you circled your hole on the Secondary Air pump hose, there is a black vacuum hose that connects to the EGR valve… Make sure hose is not broken or it will cause Codes during startup and rough starts.

Earlier I replaced the intake end of this hose. As I was removing the valve cover I discovered the EGR end is indeed completely broken. See photo with the lower circle being the broken hose.

I understand it could light up the CEL but could my P0306 be caused by this? If so, I may button my intake back up. I don’t know what else I can check on the intake.

I realize I’ve thrown a lot of info on here and the lack of responses tell me people are checking out! Stick with me please! I need to get closure on this and I’m hopeful of the day this puzzle will be solved.

[rf900rkw]

Well crap on the turbulence jet.

That's not an EGR valve. That is the secondary air injection control valve. It is only active during open loop operation right after cold start. 20 seconds and it's done. The vacuum is shut off by the little control solenoid under the rear of the manifold, so no vacuum, no leak, once the system is turned off. So SAS codes, yes. Misfire, no.

[Z3J1]

Well crap on the turbulence jet.

That's not an EGR valve. That is the secondary air injection control valve. It is only active during open loop operation right after cold start. 20 seconds and it's done. The vacuum is shut off by the little control solenoid under the rear of the manifold, so no vacuum, no leak, once the system is turned off. So SAS codes, yes. Misfire, no.

Ah phooey. Well I’ve addressed the broken secondary air hose and will soon replace the valve cover gasket, so we’ll see what happens. If that doesn’t solve the misfire code, the next culprit I may try to address is the misaligned (I think) fuel rail. And then I’m at a loss of anymore DIY fixes. Maybe I’ll send in the ECU to get looked at or just bring the car in to a BMW specialist.

[BimmerBreaker]

Ah phooey. Well I’ve addressed the broken secondary air hose and will soon replace the valve cover gasket, so we’ll see what happens. If that doesn’t solve the misfire code, the next culprit I may try to address is the misaligned (I think) fuel rail. And then I’m at a loss of anymore DIY fixes. Maybe I’ll send in the ECU to get looked at or just bring the car in to a BMW specialist.

For the fuel rail to be misaligned bad enough to cause a persistent misfire, it'd likely also not be seating the o-rings correctly, which would present as a vacuum leak (and be revealed via the smoke test). The injectors should just pop into place in the fuel rail and remain seated, the bolts should not pull the injectors down into place. Remove the fuel rail and check the condition of the injector o-rings, replace the o-rings if they are in bad condition or too dry.

If it was me, I'd replace the valve cover gasket, fix the small vacuum leak at the intake boot you observed with the smoke test and go from there. Even if the fuel trims don't indicate a vacuum leak, it would at least be prudent to rule out any existing known issues that could cause misfires and then clear the codes, reset adaptions and see how it behaves at that point

[328 Power 04]

The fuel injector for number 6 still hasn't been moved to a different cylinder for testing, has it?

[rf900rkw]

I've been operating on the assumption that #2 post 1 is true. Coil plug and injector swapped to a different hole with no change.

[Z3J1]

The fuel injector for number 6 still hasn't been moved to a different cylinder for testing, has it?

As Mr. Randy states, injector swap has been tried. Thanks to everyone for actually tracking with me!

And as BimmerBreaker recommends, I will be fixing the known issues very soon and see where we stand. One benefit of all this is that I’ve become quite competent at removing and installing the intake manifold! I must say these BMW inline engines are much easier to work on than those v6 and v8’s.

[328 Power 04]

I've been operating on the assumption that #2 post 1 is true. Coil plug and injector swapped to a different hole with no change.

As Mr. Randy states, injector swap has been tried. Thanks to everyone for actually tracking with me!

And as BimmerBreaker recommends, I will be fixing the known issues very soon and see where we stand. One benefit of all this is that I’ve become quite competent at removing and installing the intake manifold! I must say these BMW inline engines are much easier to work on than those v6 and v8’s.

Thank you for the correction, I missed that somehow.

[Z3J1]

Ugh. This cylinder 6 misfire keeps sticking around like luggage. I know you can't track this thread given you have real people in your life to tend to and all the other threads you're reading, so I'll recap what I've done so far:

1. Compression: 165-175 psi at all cylinders.
2. Coil: Swapped to different cylinder. Tried new aftermarket coils.
   
3. Injector: Swapped to different cylinder. Already using new aftermarket injectors, fresh o-rings. Tried refurbished genuine BMW injectors.
   
4. Spark plug: Swapped to different cylinder. Tried new genuine NGK BKR6EQUP 4-prong plugs. Tried new NGK BKR6E single-prong copper plugs.
5. Voltage: 12+v at each coil and injector connector.
6. CCV: Replaced.
   
7. Intake gasket: Replaced.
   
8. Throttle body gasket: Replaced.
   
9. Valve cover and spark plug tube gaskets: Replaced.
   
10. Vacuum hoses: Crusty ones replaced, including EGR hose.
    
11. Secondary air injection hose: Hole repaired.
    
12. DISA: No broken pieces. Holds vacuum.
13. Intake turbulence/secondary jets: No blockage at intake or head.
    
14. Smoke test: Tightened up leak at boot/throttle body. My transfer pump/cigar method found no other leaks.
    
15. ECU: No corrosion on connectors.
16. EDIT—- Air distribution tube on top of intake: Replaced o-rings with genuine BMW. Confirmed no blockage. Screws added since there were none.

Attached is the freeze frame of the most recent P0306.

1. Showed up a couple minutes after cold start up, just idling in the garage.
2. All cylinders are firing and runs great at WOT, until ECU shuts her down.

Here are other items I could do, based on your earlier comments and my desperation. Are any of these worth doing now?

1. Fuel rail: Realoem says part 13531433024 is for my car, but I have 14330221353. Are the dimensions different, causing injectors to be misaligned?
2. Muffler delete: Possible cause?
3. EGR: Haven’t touched it. Should I clean it?
4. ECU: Time to replace?
5. Or start from square 1 now that I’m baselined with leaky hoses and gaskets repaired?

Suggestions/therapy appreciated.

[328 Power 04]

There is no EGR in this car

Contact me if you feel like doing DME stuff. I believe I have a spare around the house.
It's not worth paying for inspection of the DME since they're so cheap used.

[Z3J1]

Contact me if you feel like doing DME stuff. I believe I have a spare around the house.
It's not worth paying for inspection of the DME since they're so cheap used.

Thank you for the offer. Will keep it in mind.

This reminds me. After all the work I’ve done should I reset the DME? I’m feeling lazy about setting up and learning INPA so hoping a BMW specialist or someone here would be willing to do it for $50 or a case of beer! Thanks