8 Cylinder Misfire After VCG Replacement

[Ximian]

Finished up work in the car after working on it intermittently for a week or so. I replaced the valve cover gasket, thin layer of Drei bond on the underside of the gasket, used fresh bolts, replaced the timing chain gasket, installed Slon Workshop covers (original, unlabelled version), replaced fuel breather valve, and brake vacuum pressure sensor. All gaskets and bolts replaced were Genuine BMW parts from FCP Euro, but fuel tank breather valve and pressure sensor were aftermarket. I triple checked the covers were on securely and fastened everywhere.

After turning the car on, I let it idle for 10 minutes and everything was working normally. Took it out for a drive and it was very responsive as usual. By this point, the engine was up to temperature, so I took it to the highway. Floored it on the on ramp and once it reached redline, instant limp mode. I captured codes and it was a misfire on cylinders 6 and 7. I turned the car off, went for an errand, and came back to a misfire on all 8 cylinders.

Codes are -

002B42, 002B43, 002B44, 002B45, 002B46, 002B47, 002B48, 002B49 (misfire cylinders 1 through 8)

002B4E Misfiring abgasverschlechternd more cylinders (emissions)

2758, 2759 Ignition cylinder (6 and 7) controlling electrical diagnostic

2796 Engine emergency program activated
2B57 Engine emergency program activated

I cleared codes and turned the car on, but instant limp mode again. I took out cylinder 4 spark plug and it was clean, no oil on it and it didn't smell like fuel. All the spark plugs are about a year old.

Since it ran well up to the red line, everything should be plugged in right. I will check the grounds on the valve covers (2 per side) to make sure they're on right (per https://www.m3post.com/forums/showthread.php?t=1701037). I'll also look into replace the fuel breather valve again reverting it to the old one to make sure that's not contributing to anything.

Pre-cat O2 sensors were replaced with Bosch parts from RM European around a month ago. I'll consider switching them back to the originals parts as well.

Next issue could be the idle control valve (per https://www.m3post.com/forums/showthread.php?t=1140555) but I'd rather not load up that parts cannon just yet.

Anything else I should be looking at?

[nycplumber]

Check your grounds

[Ximian]

Took the plenum off and checked the grounds - look fine on both sides. I don't think I even mixed up the 13 mm bolts where the short wire connects into.

Checked the resistance on the new fuel breather valve and it was 16.4 vs 16.2 on the old one, so that's working right.

Only issue I saw so far was one side of the metal clips on one injector connector was loose, but the connector securely on the injector.

Any tests on confirming an idle control valve problem?

[spammysammich]

Are the lines connected to the plenum connected and undamaged?

Specifically the line that connects at the rear and is oh so fun

[Ximian]

Originally Posted by spammysammich

Are the lines connected to the plenum connected and undamaged?

Specifically the line that connects at the rear and is oh so fun

The two in the pictures attached above? Yes, on both sides.

[spammysammich]

Originally Posted by Ximian

The two in the pictures attached above? Yes, on both sides.

No I mean the air/vacuum lines that click in under the back side of the plenum. I'm not sure of the terminology but vac leaks can cause misfires across all 8

[Ximian]

Originally Posted by spammysammich

No I mean the air/vacuum lines that click in under the back side of the plenum. I'm not sure of the terminology but vac leaks can cause misfires across all 8

Driver's side corner, that one was connected along with the two on the front of the plenum. I'll check for damage to the hose, but I was pretty careful with them.

[spammysammich]

Originally Posted by Ximian

Driver's side corner, that one was connected along with the two on the front of the plenum. I'll check for damage to the hose, but I was pretty careful with them.

The actual connector the hose snaps into can break too. Carefully inspect it.

[nycplumber]

What about linkage on throttle

[Ximian]

Originally Posted by nycplumber

What about linkage on throttle

Looks fine, I can open both easily. All 8 open as well.

[Ximian]

I had these two 13 mm posts switched, but that shouldn't matter, right? Either way, switched it back.

[Redd]

Clear codes, remove intake and plenum. Drive it and see if the codes return. If they don't you have an intake air leak somewhere.

[Ximian]

Originally Posted by Redd

Clear codes, remove intake and plenum. Drive it and see if the codes return. If they don't you have an intake air leak somewhere.

Drive with the intake and plenum removed? Wouldn't that cause more codes?

[Redd]

Originally Posted by Ximian

Drive with the intake and plenum removed? Wouldn't that cause more codes?

Yes drive without intake and plenum. DME will revert to alpha-n tune. Car will drive just fine and smooth. You will get some sensor codes but these will be different from the misfires you are getting.

[Ximian]

Haven't had much of a chance to test the car yet as I have to extract some fallen bolts from the belly pan first. I ordered an ICV that should be here in a couple of days.

I'll test the car before that to see if I still get a misfire after the battery has been disconnected for a few days and charged to 100%.

[Ximian]

Replaced the idle control valve and all good now.

Just 2379 and 27c5 from messing up the secondary air pump hose/sensor, but engine runs well overall. The sensor could have just gone bad because that seems to happen to me every other year.