01' 740 cylinder 2 misfire won't go away

[PatrickW]

Hey guys, I've spent countless hours trying to diag and resolve a P1345 code.. Cylinder 2 misfire with fuel cut. The car idles rough and under mild acceleration it will flash the CEL indicating a misfire, I can also get it to flash if I power brake it slightly at a stop but it never throws a multi cylinder misfire. Full throttle has no misfire and the cats aren't clogged. The car screams under WOT with no hesitation or break-up.

Heres what I've done so far

MAF, swapped CPS's from another running car, replaced the CCV with gasket, intake manifold gaskets and spring loaded tube, swapped injectors, swapped wiring harness, did a compression test (within 10-15%) 8 new NGK 4 prong plugs, replaced all the coils with known good ones from said parts car. I took the valve cover off when i had the intake out of the way and the only strange thing i saw was some oil that looked to be sitting on top of a closed cyl. 2 valve. The thing is there is absolutely no smoke at startup, idle or driving

Any more suggestions would be AWESOME.. I'm losing my mind with this one

[Timm]

Well, you've done all the right things in the right order. The problem doesn't really sound like a vacuum leak (such as the manifold gaskets) as that really only affects idle and should not flash the CEL on mild acceleration - but, it is worth saying that if you replace the manifold gaskets you should replace the spacers as well:

http://www.realoem.com/bmw/enUS/show...81#11611736648

....as they permanently compress just as much as the inlet manifold gaskets.

If you have INPA or Carsoft have a look at the smoothness values and let us know what they are - they can reveal a lot.

Something else that reveals a lot is the colour of the plugs you took out - was the one from cylinder 2 look any different?

The DME can fail on one cylinder - but that is permanent and at all engine settings.

So, start with the smoothness values

[PatrickW]

Plugs look new (as they are) I'm going to remove the valve covers and check the camshaft timing to the crank, I smoke tested it and tried another set of coil packs. The coil makes spark and fires everytime.

Leaning towards a mechainical issue now, if the timing is ok I'm going to remove the intake camshaft and pull the lifter tray out and inspect everything. I'll post back with what I find. Thanks guys!

[tomloans]

Plugs look new (as they are) I'm going to remove the valve covers and check the camshaft timing to the crank, I smoke tested it and tried another set of coil packs. The coil makes spark and fires everytime.

Leaning towards a mechainical issue now, if the timing is ok I'm going to remove the intake camshaft and pull the lifter tray out and inspect everything. I'll post back with what I find. Thanks guys!

How about the fuel injector...?

[xboss]

He swapped injectors but he could have an intermittent injector electrical line fail.

[Jamos]

I was going to suggest electrical as well. +1 to that

[europlus240]

Here are my thoughts on this. Since, you have already done all the basic checks for fuel and spark, I would lean towards a mechanical issue. Weak valve spring or lazy lifter may be the issue. I would rule out mutual items. MAF, oxygen sensors, clogged exhaust, fuel pump, crank position and cam position would affect more than one cylinder. I have also never seen a DME only affect one cylinder but that's me. Plus, you already replaced the harness so to me that would rule out an electrical issues. You may want to have some one help you with it. Have them recreate the misfire, while you are under the hood listening. You may hear a noise that may help you out, a stethoscope will help a lot in dictating noise difference. Obviously don't stand in front of the car if you are power braking. Hope this helps.

[kouks]

I had the same issue with my #3 cyl. Gave misfire code for a couple months. Changed fuel injector and it went away for a bit but then came back. In the end it was a head gasket leaking coolant in the cylinder. I also did not have any smoke at startup or steam. When it got really bad I looked down the spark plug hole with a strong flashlight and saw the coolant on a cold engine.

Any slightly rough idle at start that gets better after about a minute?

Losing any coolant?

I hope this is not your issue.

[Grantnz]

Run a compression test and see how the faulty cylinder stacks up.

[PatrickW]

Ran a compression test and everything is within 10-15%. I am not losing any coolant. Just pulled the valve covers off and checked timing which seems to be fine, using the BAS instructions and tools. Chain tension seems fine as well, guess its time to pull the cams out and see whats up. Thanks for your input guys

Side Note: working on getting the older factory diag software however I feel this is certainly a mechanical issue so I will procede with dissasembly.