Misfire Cylinder 1
 

Hopefully there is a E53/M54 wizard out there that can assist me. Will list things out in point form so it's easier to follow progression of the problem.

1. 2002 E53, 444,000Km - engine was running perfectly, until I parked it for 10 days over the Thanksgiving break.

2. Tried to start after thanksgiving - no go - thought it was the starter or battery so replaced starter and batt was fine, but no start. This issue turned out to be no compression due apparently to hydraulic lifters losing pressure from sitting so long (?). Ended up getting it to start by just cranking it for like 90 secs till compression returned. It seemed to run fine after that.

3. Drove it for about 130 km - all good, until I got on freeway and accelerated up to speed - moments later it started running rough and I got a "misfire cyc 1 with fuel shutoff" error code.

4. Installed new plugs, swapped Cyc1 and Cyc2 coil packs to see if issue moved. Started fine but again under heavy load, misfire Cyc1 returns. Swapped out Cyc1 injector. Verified all elec connections to injectors are solid. No change, same thing on next test drive. The Cyc1 injector does indeed appear to shutoff when the issue occurs (cannot hear it firing/clicking via stethoscope/screwdriver), so maybe the ECU is shutting it down? Question is why.

5. Exhaust is fumy (been that way for a few years) largely because either downstream O2s are bad (not likely) or the aftermarket Cat is crap and probably failed after 6 mo (more likely). Not sure if the fumy exhaust could lead to current issue with misfire Cyc1, but aware of that issue and will look at new O2s once I slay this misfiring dragon.

6. Further background info - When I had the plenum off to change out the starter, I replaced the crankshaft sensor (put new one in since it was accessible with starter out), cleaned the injectors, CCV system is less than year old (inspected all hoses associated with it - all good), inspected/replaced any bad vac hoses, DISA, ISV, MAF, throttle body all in good working order.

Anyone have any ideas? Thanks in advance.

FUEL AIR SPARK these are the 3 things i would make sure are working well...if plugs are new, coils are new, injectors working then I would look at the Fuel Pump? you are at a mileage where most Fuel Pump fail.
I ask you to check out E46fanatics and some important links under GENERAl Info especially the section diagnosing Fuel trim misfires etc etc etc....M54 problems tend to extend to ALL the platforms that use these engines...
FYI_ I had just went thru a single cylinder misfire that turned out to be a soft failing 165k mile original BMW fuel pump.

All is well now post replacement.

Do a compression test. The DME will cut out a cylinder that isn't performing properly for emissions reasons. Resetting adaptations or I think just clearing the codes will start the injector up again for a time.

Thanks for responding.

Fuel pump is not that old, and one of the first things I checked when the previous hard start/no start problem occurred was the fuel pressure - was up above 50 psi. Will check the links you reference. I will also check the fuel pressure again.

A bit more on the issue. If I reset the error codes the rough running and misfire immediately goes away, so clearly, whatever this is, it would appear that the ECU is turning off the injector feeding Cyc1.

Engine also runs fine if I turn it off and back on, and it idles perfectly. It is ONLY when I throw the throttle down and get the RPM above 3700 RPM that the shutdown of fuel to Injector 1 seems to occur. Now, more I think about this, that could be fuel pressure related, or fuel constriction related since demand for the fuel increases, but why only Cyc1 being affected? Cyc 1 IS however the Cylinder at the end of the fuel rail but cannot imagine that has a bearing on the problem. The quest continues.

Yup - correct - when I clear code the DME turns that injector back on immediately. Will look at compression.

Checked the fuel pressure this morning on start, idle, revving the engine above 3500 RPM, and then took it for a test drive to produce the rough running problem (which only happens when the engine is under load - I cannot produce the problem by just revving the engine while parked). Once I was able to generate the problem where Inj 1 is shutdown by the ECU, I checked fuel pressure again. In all scenarios described above, fuel pressure sits at 50 psi, so, I do not think my issue is fuel pump, or fuel filter related. As mentioned both fuel pump and filter are not that old.

One thing I DID note using my Torque app; while the rough running/injector 1 shutoff occurs, the voltages from all O2 sensors is 0 (i.e no up/down oscillating the way they do normally), so whatever is going on, it appears the ECU not only turns off injector 1, but the feedback loop from the O2 sensors is also disabled by the ECU (?). When I erase the ODB codes the injector is turned back on by the ECU, the O2 sensors are also back online. I am curious to know which came first, the injector shutting down, or the sensors being turned off (assuming there is some relevance between those two elements).

Compression test is next in the queue.....

And here are the compression test results:


CY1 CY2 CY3 CY4 CY5 CY6
PSI PSI PSI PSI PSI PSI
170 170 170 180 170 170

Sooo, does not look like my issue is necessarily a compression problem. Took it for another test and every time, and soon as I load up the engine (accelerate with revs above 3800 RPM), it shudders a bit, looses power, and then that injector is turned off. Wonder if the Cyc 1 exhaust port is clogged up with carbon or something?

Next step is to look at replacing the O2 sensors but, I doubt that is my issue, since they are not THAT old.

It's not really clear on your post but you need to 'monitor' the fuel pressure under load when the problem happens to rule that out. Spark is the next most likely thing, switching coils doesn't always rule out the coils or a spark problem. A weak cylinder, for whatever reason, usually needs more spark. Maybe try reducing the plug gap and see what that does.

Is the cyl 1 misfire the only code you get?

What are you using to scan for codes? Some apps like torque won't pull all the codes compared to INPA/ISTA

I think you did something when you pulled the intake..You should go over your work and consider pulling the intake again.

How did you deal with fuel rail on the orig intake pull? Did you unclip the long elec harness at each injector or did you pull rail and harness together.. you might pull elec connector and see if pins are bent and/or if it is fully seated at injector 1..

Any chance the intake gasket is folded over at the front? Did you replace the gasket?

Yup - thought of that (monitoring during load) - admittedly, I did not have the fuel pressure gauge rigged up when I did the test drive, only after the ECU turned off the injector did I check fuel pressure again. I guess I can rig up with gauge carefully and try monitoring it under load.

The problem ONLY happens once I get the revs up over 3500 RPM while accelerating. If I drive the car around and keep revs below 3500, everything seems normal.

I am starting to wonder the same thing (I may have messed something up on the intake pull). This thing WAS running PERFECTLY before the aforementioned hard start issue that was resolved.

When I removed the fuel rail, I took the injector harness off first (it is sorta hard to get at the fuel rail bolts without removing the injector wire harness.) I have since taken the inj harness back off to look at the connections, and I also put a different injector in cyc 1. All connections on the harness looked good. When removing the harness, I flipped the positive latch clips off prior to removing it from the injectors. The injector I took out, and the one I put in to replace it, were both tested on my bench for leak during shutoff, as well as spray pattern - both looked good on both injectors.

Your comment on the plenum gasket is similar thought I had earlier today - I was wondering if perhaps unmetered air is getting sucked in there under load through that gasket not sealing properly. Was thinking of maybe trying to do a smoke test around that area, although that is a bit tricky to do since there is a lot of ambient air movement in that region of the engine generated by the rad fan which sits inches away from the front cylinder, and, this issue needs the engine loaded up to happen, so not sure how effective a smoke test would be. Would have to find a way to shield the area from the effects of the rad fan. One would think if there was unmetered air seeping in at the intake man for cyc1, I should be seeing other error codes popping up. Incidentally, I am using Torque as well as another scan tool that has support for more of the BMW codes. I did not replace the gasket between the intake plenum and the head on my recent intake removal, since I had put a new gasket on less than a year ago when I did the CCV system. That might have been a mistake, but the gasket was in excellent condition.

Methinks I might have another intake pull in my near future to verify if that gasket is sealing properly.....ugh. Running out of other ideas.

So did another road test this morning with the fuel pressure gauge visible from the drivers seat so I could monitor pressure during the road test. Accelerated up with revs up to 4000 RPM - when the issue occurs, fuel pressure does not budge from the 50psi mark, so pretty confident the issue is not fuel pump/filter related.

I was lurking a bit to see how things would play out but I'll throw in my 2 cents.

My issue was sort of the reverse of what you are experiencing but the symptoms are quite similar.

During idle it would trigger misfires and run very rough. If I turned off the engine and restarted it would run fine until you hit the first red light. If I kept the RPM up over 2k and then quickly put it in drive it wouldn't exhibit the misfire.

Replaced the CCV, swapped out the idle air, coils and all the usual suspects without being able to get rid of the stumble at idle.

Finally I built myself a poor man's smoke tester and noticed smoke coming from "the middle" of somewhere. Seeing as pretty much everything else that was a gasket had been replaced my logic said to replace the gasket on the intake manifold and that did the trick.

I found a gasket on amazon for about $10 and it's been behaving ever since.

In my case I didn't even disconnect the fuel rail. Just lifted the intake off enough to replace the gasket.

You can read all about my experience here https://xoutpost.com/bmw-sav-forums/...hate-bmws.html

Also, the ambient air/fan issue you're thinking of is non existent when you're doing a smoke test because the engine is off...right?

Hi - yup if you pressurize the plenum with smoke that could definitely localize a vacuum leak, or in your case, a gasket leak. In my case, my problem only happens when I rev the engine, under load, above 5000 RPM now, so not sure a standard smoke test will help me, but, I will give it a try next week before I go pulling the intake plenum off again. My engine idles perfectly, and runs super smooth, as long as I never rev above 5000 RPM (its not like I am up in those revs very often, but there is an issue, so I need to figure it out). It is only when I accelerate to come up to highway speed (for example) that the issue shows up. Otherwise the thing runs really nice. I replaced my CCV and all the vac lines a year ago, so I know those are all in good order.

I'm surprised you were able to get to all the nuts that secure the plenum to the intake without removing the rail - the rail/harness assembly kinda blocks access to some of those nuts. I guess with the right universal attachment you can get to them. On that note, I will go double check that mine are all secured as well.

Thanks for the comments. My quest continues. Will see if I can find anything with my homebrew smoker this coming week.

Just the harness connectors are in the way. No u-joints or any other tools than a socket and extension.

Well, smoke test is negative - cannot see any leaks from the plenum or from where it mates with the intake. The other item of note is last 3 test drives I am no longer able to produce the problem.....grrrrrrr!

Okay .I've read on E46fanatics as I was going thru my single cylinder misfire problem- a member found defective or shorted cylinder 6 on the DME.
If all else is negative , I think it will be worthwhile to open up your DME .

Sorry can you be a bit more specific? Do you mean a shorted or loose pin on the DME cable harness, or something wrong with the logic board in the DME itself that caused the DME to periodically shutdown that cylinder?

Thanks for the feedback.

It's worth checking the DME connections for corrosion (water intrusion), but that is likely not your issue.

I still think its an awfully big coincidence that all this happened after your intake R&R...although I would wait for it to reappear before pulling intake.

as EFFDURATION has mentioned- may or may not be your issue but something to think about if the misfire comes back.
DME connectors/harness and the DME itself(yes the board itself), make sure there is no problem with Driver #1.

As part of all the trouble shooting, I did get into the engine bay relay box to pull the DME relay to facilitate the compression test. While in there I did check the DME harness and connections etc - no water intrusion but, might be worth going back and pulling the plugs off the DME and inspecting them more closely.

Other issue I know I have is some carbon buildup in the exhaust man/down pipes so I need to go tackle that as well - that is likely being caused by over fueling due to (I believe) a shitty after market installed a few years ago which seemed to work fine for about 6 mo and then I started getting cat efficiency errors on both banks.

The first thing to do with a single cylinder misfire is to swap one coil with that from another cylinder. You have a misfire on Cyl 1, so swap the coil with Cyl 4, then walk away.

Drive the car and wait for the misfire to return, it should be on 1 or on 4, if it follows the coil, then you have a bad coil OR the boot between the coil and the plug. If the misfire stays on the same cylinder, then you have a bad plug of fuel injection issues, or a signal problem where the computer is not telling the coil to fire. You could have compressiopn troubles, but you already checked this and the numbers look good.

Thanks for the reply. Yup - that was the first thing I did - moved the coil to another cyc. Problem did not follow the coil. New plugs, swapped injector, and cleaned them all, checked connections on harness. Issue now appears to have gone away, so I have given up now until it returns.

When it comes back you could try reducing the sparkplug gap on the missing cylinder. If that helps then you probably are not getting enough secondary coil voltage for what ever reason, if it gets worse then you might be back to looking for a fuel issue maybe from the injector itself. You can damage an injector really fast by bench testing it.

There is a lot in your first post that doesn't make sense. Not starting because the lifters have leaked down isn't really a thing. Why did you replace the starter in the first place? How did you clean the injectors?

Thanks for reply. I actually put a new set of plugs in. Also swapped out the injector and coil pack on cyc 1.

I do not think my initial issue had anything to do with the misfire problem (notwithstanding me creating the misfire issue with my efforts to swap out the starter, which involved my removing the intake plenum). I had that hard starting problem in the past btw (a few years back and I had forgotten about it) where, if I do not start the car for over a week, it is hard to start the first time - I zeroed in (mistakenly) on the starter thinking it was not cranking properly, as the sound of the cranking was not normal (that was because there was no compression due to the lifter bleed down). I sent a recording of the cranking sound to my BMW Wizard friend, and he instantly recognized that sound as cranking with no compression. I misread that problem in the beginning as being the starter, and as it turned out, my starter was just fine.

re Injector Testing: I built a test jig for cleaning injectors - I use an injector cleaning agent, under small amount of pressure, and a 9V battery to turn on and off the valve - that allows me to check the spray pattern, and verify it is shutting off properly. Have been doing that for years and never had a problem. As I said, I have put a different injector in cyc1 and no difference.

One other thing I did when I replaced the starter was I put a new (non-OEM however) crankshaft position sensor in, since it was easily accessible when I had the starter out, and figured it was an opportune time to replace the 20 year old factory one. Don't know if that would be a contributing factor to the misfire - again the engine purrs beautifully, as long as I do not load it up above 5500 RPM.

Thanks again for all your suggestions.