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.