[learjet23a]

So after my dismal results with crappy compression tester, I decided to purchase a leak down tester to determine if I have any leakage in my cylinders especially 4/5/6. To my delight I have very little to no leakage in any of the cylinders, I pumped 90psi into each at TDC and only heard a faint consistent air leak thru the oil filler cap, I assume due to age and condition of piston rings some leakage is normal, no air at throttle body or exhaust.

I removed the dme harness X60006 and both the connector terminals and pins looked excellent, I'm really struggling for next moves here, maybe need to investigate the injectors further... I have spark as previously determined at each coil my plugs look pretty consistently black ( see attached pic ) keep in mind these were pretty heavily fuel soaked during the crank no start situation.

[fastboatster]

That last plug looks awful and probably would cause misfires on its own, I think you should try to start the engine with a set of fresh plugs

[SlowE92]

Originally Posted by learjet23a

So after my dismal results with crappy compression tester, I decided to purchase a leak down tester to determine if I have any leakage in my cylinders especially 4/5/6. To my delight I have very little to no leakage in any of the cylinders, I pumped 90psi into each at TDC and only heard a faint consistent air leak thru the oil filler cap, I assume due to age and condition of piston rings some leakage is normal, no air at throttle body or exhaust.

I removed the dme harness X60006 and both the connector terminals and pins looked excellent, I'm really struggling for next moves here, maybe need to investigate the injectors further... I have spark as previously determined at each coil my plugs look pretty consistently black ( see attached pic ) keep in mind these were pretty heavily fuel soaked during the crank no start situation.

Definitely change those plugs, they're extra crispy.

[learjet23a]

Haha ok, I'll change them I'm such a cheap ass!

[learjet23a]

Went ahead and replaced all the spark plugs, while the vehicle initially started and sounded pretty good within approx 30 seconds it started to miss badly exhibiting all the previous symptoms and fault codes.. I immediately pulled all the new plugs to find cyl 1/2 looked clean and newish whilst 3/4/5/6 all were carbon fouled (sooty) Something is causing a rich condition. Might be time for me to bring to the shop unless anyone can chime in with more trouble shooting ideas... pic below left is from cyl 1/2 and right is 3-4-5-6

[SlowE92]

Originally Posted by learjet23a

Went ahead and replaced all the spark plugs, while the vehicle initially started and sounded pretty good within approx 30 seconds it started to miss badly exhibiting all the previous symptoms and fault codes.. I immediately pulled all the new plugs to find cyl 1/2 looked clean and newish whilst 3/4/5/6 all were carbon fouled (sooty) Something is causing a rich condition. Might be time for me to bring to the shop unless anyone can chime in with more trouble shooting ideas... pic below left is from cyl 1/2 and right is 3-4-5-6

Have you tried swapping injectors? Try swapping injectors 1 and 2 to 3 and 4 and see if the misfire moves.

[learjet23a]

Ok I can try that do I need to worry about recoding them?

[SlowE92]

Originally Posted by learjet23a

Ok I can try that do I need to worry about recoding them?

No, I wouldn't worry about that.

[SlowE92]

Originally Posted by learjet23a

Ok I can try that do I need to worry about recoding them?

If you've done plugs the only things left are coils and injectors. Try swapping coils too and see if the misfires move.

[wheela]

I haven't replaced injectors myself, but I know each individual injector flows slighlty differently, which is why you want to recode when swapping them out. I don't know if they can vary enough to cause a misfire, but since that's what you're trying to track down, if it was my car I'd recode even if just temporarily swapping them for testing purposes. It would suck to go to the trouble of swapping injectors and not knowing if not coding was the cause for misfires, if they persist after the swap.

I agree that coils and injectors are logical culprits for misfires, but I can't stop thinking about the fact you had none before removing/replacing the valve cover, now you have misfires on 4 cylinders immediately after removing/replacing the valve cover??? Not sure how that procedure could impact function of your coils or injectors on 4 cylinders, unless wiring got damaged/reconnected incorrectly? Did you go back and double check all wiring?

For O2 sensors, I believe the connectors are physically the same, but the harness shroud is a different color, so it may be physically possible to inadvertantly swap connectors on reassembly - here's a pic of my O2 connectors, note the order of grey and black harness shroud. Also for the injectors and coils, I don't recall if there is enough wire slack to connect them to the wrong cylinder, but would be good to double-check. I just have a tough time seeing how 4 injectors or coils could go bad while removing/replacing a valve cover

[learjet23a]

Originally Posted by wheela

I haven't replaced injectors myself, but I know each individual injector flows slighlty differently, which is why you want to recode when swapping them out. I don't know if they can vary enough to cause a misfire, but since that's what you're trying to track down, if it was my car I'd recode even if just temporarily swapping them for testing purposes. It would suck to go to the trouble of swapping injectors and not knowing if not coding was the cause for misfires, if they persist after the swap.

I agree that coils and injectors are logical culprits for misfires, but I can't stop thinking about the fact you had none before removing/replacing the valve cover, now you have misfires on 4 cylinders immediately after removing/replacing the valve cover??? Not sure how that procedure could impact function of your coils or injectors on 4 cylinders, unless wiring got damaged/reconnected incorrectly? Did you go back and double check all wiring?

For O2 sensors, I believe the connectors are physically the same, but the harness shroud is a different color, so it may be physically possible to inadvertantly swap connectors on reassembly - here's a pic of my O2 connectors, note the order of grey and black harness shroud. Also for the injectors and coils, I don't recall if there is enough wire slack to connect them to the wrong cylinder, but would be good to double-check. I just have a tough time seeing how 4 injectors or coils could go bad while removing/replacing a valve cover

On my vehicle model you CANNOT interchange the two O2 sensor plugs the harness are physically different and are pinned differently, plus I did actually mark the harness before removing.

I know the coils aren't likely the issue as I tested spark at each cylinder and have rotated the coils many times and the misfire will always be the same cylinders.

I did look over the wiring visually and removed the harness from the ECU to inspect pins etc... all looks well, plus after initial reassembly of valve cover the car ran fine for almost 30min if it were electrical I think it would have been immediate, I think its something with the intake cam phasing see BELOW>

Just to recap the WHOLE history of this issue you may or may not recall I had a post going "crank no start n55". The issue started with a valve cover R/I, I removed the bearing caps from my intake cam to inspect for wear. After reassembly the car started and drove perfectly for about 30 min before check engine, poor Idle left me on the side of the road. After checking codes I got Misfire on 4/5/6. Nothing worked to restart, only after disconnecting the VVT Actuator did it allowed me to drive almost home before stalling for good unable to restart. Initially yes I was looking into electrical issues however in the end I re-opened the valve cover and discovered TWO things, firstly the Timing was off! Only the Intake cam was out, advanced approx 90deg clockwise. I noticed the bearing caps were also loose, somehow even thou I torqued them to the correct 8.5 NM they worked themselves loose probably leading to the cam somehow going out of phase. After putting to correct time and reassembly it brings us to today, car will start run poorly and still has the misfire codes on 4/5/6 with fuel cut.

[wheela]

Thanks for the recap on everything, I was forgetting some of the details. I agree, this seems to rule out an issue with wiring.

Back to injectors - earlier I mentioned I couldn't see how they'd go bad from removing/replacing the valve cover, but I hadn't thought of potential contamination getting in the lines while they were opened up. If that happened, any grit/etc. could work it's way down to the injectors and start to clog them.

After re-reading your summary, I could see the bearing caps working loose and timing going further and further out until the car couldn't run. That would explain it initially running well, then getting worse and worse unitil it gave up for good. Then you fix the timing issue, but if some crud had gotten in the fuel lines while they were open, maybe now you're dealing with misfires from clogged injectors? As previously mentioned, injectors are probably the next step, at least now I can see a potential reason why they may be acting up after valve cover removal.

[fastboatster]

I have also reread your recap. You said you removed intake cam caps, I sort of assumed that you did it just like the service manual says - removed valvetronic shaft and lots of other prescribed things. Now it looks like it wasn’t the case and you just pull the intake cam caps without doing all that. It makes sense that some caps turned out to be loose, they were tightened when the valve springs were pushing on the cam via intermediate shaft, that pressure affected felt torque for sure. I’d say you need to redo this following the factory procedure which involves removing valvetronic components and inspect everything. Who knows what got bent or damaged. Or have a specialized shop do it for you, which probably a safer option at this point

[learjet23a]

Originally Posted by fastboatster

I have also reread your recap. You said you removed intake cam caps, I sort of assumed that you did it just like the service manual says - removed valvetronic shaft and lots of other prescribed things. Now it looks like it wasn’t the case and you just pull the intake cam caps without doing all that. It makes sense that some caps turned out to be loose, they were tightened when the valve springs were pushing on the cam via intermediate shaft, that pressure affected felt torque for sure. I’d say you need to redo this following the factory procedure which involves removing valvetronic components and inspect everything. Who knows what got bent or damaged. Or have a specialized shop do it for you, which probably a safer option at this point

I removed the caps one at a time and torqued each one before moving to the next. From my investigation this should not cause any issues. Having said that it did come loose so something went wrong!

[SlowE92]

Originally Posted by learjet23a

I removed the caps one at a time and torqued each one before moving to the next. From my investigation this should not cause any issues. Having said that it did come loose so something went wrong!

It sounds to me like you originally had a fault with the injectors/possibly valvetronic? I'd rule out plugs and coils because its quite uncommon for all 3 to go out simutaneously but its not unheard of. VVT sounds right because unplugging it allowed you to drive normally for a small while until you stalled out. And thats why you were possibly misfiring. Did you by chance swap the injectors out?

[SlowE92]

Originally Posted by learjet23a

On my vehicle model you CANNOT interchange the two O2 sensor plugs the harness are physically different and are pinned differently, plus I did actually mark the harness before removing.

I know the coils aren't likely the issue as I tested spark at each cylinder and have rotated the coils many times and the misfire will always be the same cylinders.

I did look over the wiring visually and removed the harness from the ECU to inspect pins etc... all looks well, plus after initial reassembly of valve cover the car ran fine for almost 30min if it were electrical I think it would have been immediate, I think its something with the intake cam phasing see BELOW>

Just to recap the WHOLE history of this issue you may or may not recall I had a post going "crank no start n55". The issue started with a valve cover R/I, I removed the bearing caps from my intake cam to inspect for wear. After reassembly the car started and drove perfectly for about 30 min before check engine, poor Idle left me on the side of the road. After checking codes I got Misfire on 4/5/6. Nothing worked to restart, only after disconnecting the VVT Actuator did it allowed me to drive almost home before stalling for good unable to restart. Initially yes I was looking into electrical issues however in the end I re-opened the valve cover and discovered TWO things, firstly the Timing was off! Only the Intake cam was out, advanced approx 90deg clockwise. I noticed the bearing caps were also loose, somehow even thou I torqued them to the correct 8.5 NM they worked themselves loose probably leading to the cam somehow going out of phase. After putting to correct time and reassembly it brings us to today, car will start run poorly and still has the misfire codes on 4/5/6 with fuel cut.

However the eccentric shaft controls the lift valves for the intake, through the valvetronic motor, and unplugging the VVT connection could be the reason that your intake timing was off as well.

[wheela]

Originally Posted by MakoB96

It sounds to me like you originally had a fault with the injectors/possibly valvetronic? I'd rule out plugs and coils because its quite uncommon for all 3 to go out simutaneously but its not unheard of. VVT sounds right because unplugging it allowed you to drive normally for a small while until you stalled out. And thats why you were possibly misfiring. Did you by chance swap the injectors out?

I think the vvt may be a bit of a red hearing here. At part throttle, because of valvetronic the intake valves only open a few mm (vs. The maximum is 8 or 9mm, I can't remember which). So if the intake cam bearing caps were working loose, the cam would be rotating off axis and not opening the valves as far as they should. For example, maybe vvt was targeting 2mm lift and only getting 1mm due to the loose bearing caps. If valvetronic motor was unplugged at maximum lift, that could have compensated for the lift lost due to loose bearing caps on the intake cam, at least for a bit until the bearings caps loosened more to the point of running out of valve lift again. I don't think valvetronic can influence timing of the intake valves at all.

I agree with fastboatster, if the engine was running with loose bearing caps and the intake cam jumped a total of 90 degrees of timing while running, did any of those components get damaged while running in the loosened state? If they did, I'm not sure if that would explain misfire on only 4 of 6 cylinders though.

I'm still wondering if some contamination got in the hp lines while the valve cover was off, and now some partially clogged injectors are causing misfires? But I'm just spit balling here based on my rudimentary understanding of the system, I'm not a mechanic, and have never even removed my valve cover.

[SlowE92]

Originally Posted by wheela

I think the vvt may be a bit of a red hearing here. At part throttle, because of valvetronic the intake valves only open a few mm (vs. The maximum is 8 or 9mm, I can't remember which). So if the intake cam bearing caps were working loose, the cam would be rotating off axis and not opening the valves as far as they should. For example, maybe vvt was targeting 2mm lift and only getting 1mm due to the loose bearing caps. If valvetronic motor was unplugged at maximum lift, that could have compensated for the lift lost due to loose bearing caps on the intake cam, at least for a bit until the bearings caps loosened more to the point of running out of valve lift again. I don't think valvetronic can influence timing of the intake valves at all.

I agree with fastboatster, if the engine was running with loose bearing caps and the intake cam jumped a total of 90 degrees of timing while running, did any of those components get damaged while running in the loosened state? If they did, I'm not sure if that would explain misfire on only 4 of 6 cylinders though.

I'm still wondering if some contamination got in the hp lines while the valve cover was off, and now some partially clogged injectors are causing misfires? But I'm just spit balling here based on my rudimentary understanding of the system, I'm not a mechanic, and have never even removed my valve cover.

Valvetronic regulates the intake cam via the eccentric shaft. If the valvetronic motor is bad or eccentric shaft sensor then the car is running off the tb. The tb is more of a fail safe and is always in the wot position when valvetronic is operating. If by unplugging the valvetronic the car operates normally then I wouldn't rule it out, especially if the car was running like crap or wouldn't start, is also a tall tale sign of bad valvetronic. I'm not 100% sure but I think unplugging it sends the camshaft to the default position? I know unplugging the vanos does but I'm not sure about the valvetronic connection.

[SlowE92]

Originally Posted by wheela

I think the vvt may be a bit of a red hearing here. At part throttle, because of valvetronic the intake valves only open a few mm (vs. The maximum is 8 or 9mm, I can't remember which). So if the intake cam bearing caps were working loose, the cam would be rotating off axis and not opening the valves as far as they should. For example, maybe vvt was targeting 2mm lift and only getting 1mm due to the loose bearing caps. If valvetronic motor was unplugged at maximum lift, that could have compensated for the lift lost due to loose bearing caps on the intake cam, at least for a bit until the bearings caps loosened more to the point of running out of valve lift again. I don't think valvetronic can influence timing of the intake valves at all.

I agree with fastboatster, if the engine was running with loose bearing caps and the intake cam jumped a total of 90 degrees of timing while running, did any of those components get damaged while running in the loosened state? If they did, I'm not sure if that would explain misfire on only 4 of 6 cylinders though.

I'm still wondering if some contamination got in the hp lines while the valve cover was off, and now some partially clogged injectors are causing misfires? But I'm just spit balling here based on my rudimentary understanding of the system, I'm not a mechanic, and have never even removed my valve cover.

In all honesty your guess is as good as mine. Loose bearing caps could jump the timing. I think OP stated that he checked the valves previously but I don't remember, I remember telling him to remove his manifold and check the sides of them.

[fastboatster]

So here’s a great video about valvetronic installation, notice that at around 10:24 or around that he’s talking about cam followers popping out of place and needing to set them straight:

Looking at pic #3 in the post with pics with valve cover removed, the cam lobes look scratched. Maybe some of these followers are not sitting correctly. But that will be something a shop will need to check, as this is my final advice - get this car to the shop

[learjet23a]

Originally Posted by fastboatster

So here’s a great video about valvetronic installation, notice that at around 10:24 or around that he’s talking about cam followers popping out of place and needing to set them straight:

Looking at pic #3 in the post with pics with valve cover removed, the cam lobes look scratched. Maybe some of these followers are not sitting correctly. But that will be something a shop will need to check, as this is my final advice - get this car to the shop

Okay Fastboatster called it right, I pooched the intake cam something fierce! Looking back the only logical explanation for all this crap lead back to my intake cam service. I decided to pull the valve cover for I think the 5th or 6th time now... I managed to do it now in 12min flat! Anyway the story is now clear after removing the intake bearing caps again...1st cap closest to front of engine and cylinders 1/2 are flawless, which explains the cylinder compression results. Cylinder 3/4/5/6 look absolutely awful, clearly the intake cam had come loose and banged out the caps and by the looks of it chewed up the intake cam journals and head side as well unfortunately. After looking very carefully at the lifters/rockers/valve spring assemblies look good, seems the damage is centred around the camshaft and bearing journals. So what do I do now? I'm sorry I'm likely not going to bring this to a shop I feel I'm capable of this repair provided I have the parts on hand. Can one purchase a used head and move all the internals over? Or search for a head with internals ? I need to get this thing on the road again....

[learjet23a]

Well, not sure if any of you are interested but I did successfully replace the entire head on my N55. It was an incredibly difficult job with the engine in the car but I muddled thru it. Worst part was the machining of 3 holes I needed in order to fit the newer style recessed spark-plug inserts!

Car runs great only issue is I'm right back where I started with this damn 28A0 (P112F). Ista did give a brief Lean code not sure if that might lend a hint. I guess I can rule out the head and internals this time round.. Any idea where to go? I have thoroughly smoke tested the intake and crankcase. Inspected and cleaned the MAF/TMAP and throttle body and preformed adaptations in ISTA as well as the fuel vent disconnect.