Misfires/ Poor Idle

Originally Posted by gesoffen

That will do it..... as well as make a mess on the exhaust side of your head! When replacing the gasket a couple of potential might as wells:

- consider replacing the valve cover itself (they're plastic and are brittle by 10yr/100k+, thus VERY easy to crack when you're torquing them back down). They come with the perimeter and spark plug gaskets so at ~$200 for the cover, you're "only" paying ~$160 more than for the gasket alone. It'll also save you the aggravation of removing the old cracked/brittle gasket from the your valve cover.
- replace all the rubber sealing bushings for all the VC bolts - 15 total on an M54 engine
- By a yard/meter of 5.6mm/1.4" vacuum hose and replace the line that runs to the SAP valve (front passenger side corner of head around back to center of head under where the cabin filter sits). Its a hard pipe connected at either end by the vacuum hose and the portion on the passenger side is usually toast by now from the heat of the manifold.

All in all, this is a fairly easy but a bit messy DIY. Good luck!

I had both the cover and gasket replaced when I bought the car with 100k miles on it. I now have 150k. Is the cover really going to be that bad?

Sent from my LS670 using Bimmer App

Well I haven't changed the gasket our cover yet but I changed the plugs again this time with NGK laser platinums and cleared my CEL light. It has been 3 days now and my light has not come back on and it seems to be running just fine now. I'm not sure if changing the disa along with plugs was the answer but I guess time wil tell? Any thoughts?

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Dude I'm having the same problem with my car too rough idle and no balls when u step on it LOL

Start with cleaning your ICV with some carb cleaner and inspecting your entire intake for cracks and leaks.

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Some hopefully useful info: I had the Misfire on all cylinders code, bank 1 & 2 too lean codes, and horribly rough idle, not to mention sh!t gas mileage, disconnected my MAF and the car ran a little more smoothly but still rough at idle. I replaced my Disa, connected my MAF sensor and saddly enough my SES light was still on. I ran the car for about 40 miles with roughly 10 cycles of turning my car off and back on, and bam, my SES light is off, and the car is running much more smoothly. I still plan on cleaning my ICV and doing a plugs and wires change along with a fuel filter change (105K its about time) but she goes when I hit the fun time pedall

Well its been 750 miles since i thought i had fixed my issues but while driving my CEL came back on. I checked the code when i got to my destination and i got a code for MAF circuit high. i popped my hood and found my MAF harness had magicly disconnected itself. I reconnected it and cleared the code. When i went to start my journey home the light came back on and once again i checked the codes and i popped the following codes. I cleared them out and drove a few cycles on the engine and they all came back.

P0300 Random/Multiple Cylinder Misfire Detected
P1346 Misfire During Start Cylinder 3
P1349 Misfire Cylinder 4 With Fuel Cut-off
P1351 Misfire Cylinder 5 With Fuel Cut-off
P1343 Misfire Cylinder 1 With Fuel Cut-off
P0171 Fuel System Too Lean (Bank 1)
P0174 Fuel System Too Lean (Bank 2)

Pending
P0300 Random/Multiple Cylinder Misfire Detected.

Im a complete loss for words as to WTF is going on now. I was going to change the VCG because i thought i had an oil leak there and it would be the cause of my issues. But since i replaced the DISA valve that had a broken spring I havent lossed any oil what so ever so i think im ruling the VCG out.

I am reasonably sure your problem is related to the valve cover gasket and/or CVV and hoses. My friend (who shall remain nameless to protect his ignorance) told me his car was running like crap. I scanned it and got almost the exact same set of codes. Perplexed I asked "did you do anything to your car recently?". The only thing he had done was put some oil in it. So I pop his hood and immediately spot the problem. He forgot to replace the oil cap. That is a BIG valve cover leak. Yours is likely the culprit too.

Even though I don't seem to be losing oil?

I guess I don't understand how it was symptom free for so many miles and then BOOM my demons are back

damn, it sucks you still have to go through this again. for my car, i had similar codes and my car ran alitle ****ty, because i had a head gasket leak, small leak, eventually the leak got worse down the road. once i replaced my head gasket, all the misfire codes went away. the only issue i have now is my torque converter, the P0741. I ordered one about a couple days ago and will replace my bad one. I hope you resolve your issues soon.

Originally Posted by BROOKSBC

I guess I don't understand how it was symptom free for so many miles and then BOOM my demons are back

Who knows. A smoke test would likely find the problem too. You might want to go that route. But knowing how cheap and easy the VCG is, why not give it a shot?

could be a number of things. had this bmw that had a vacuum leak with same lean codes just as you and it turns out whoever installed valve cover gasket tightened the middle bolts too tight n cracked the valve cover. smoking it was the only way to find it.

Originally Posted by smolck

Who knows. A smoke test would likely find the problem too. You might want to go that route. But knowing how cheap and easy the VCG is, why not give it a shot?

Well I guess I will give it a shot. Should I do the cvv at the same time?

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If the cvv is the original one, its over due. Even if the unit itself hasn't failed, the hoses and fittings are brittle and chances they'll fail in the near future. You have to disconnect the fitting from the cvv to the valve cover and there is a good possibility, the fitting will break if its original.

Unfortunately, the cvv system is on the opposite side of the engine from the valve cover so there is only a small amount of overlap in removing parts for access.

So my oil change has been well over due. I've been putting it off while trying to diagnose this situation. Today I changed the oil since I'm making a long trip (550 miles). After changing the oil my CEL went out for about 5 mins and then came back with the these codes in order,

P0174
P0171

Pending
P0143
P0151
P0144

I'm going to assume the other codes will come back as well but I just wanted to post this update for anybody who is following this thread.

Originally Posted by gesoffen

If the cvv is the original one, its over due. Even if the unit itself hasn't failed, the hoses and fittings are brittle and chances they'll fail in the near future. You have to disconnect the fitting from the cvv to the valve cover and there is a good possibility, the fitting will break if its original.

Unfortunately, the cvv system is on the opposite side of the engine from the valve cover so there is only a small amount of overlap in removing parts for access.

The previous and first owner did not care for it much so I'm sure it's the original. I've already replaced the vent tube that leads from below the vanos solenoid. It snapped off at the elbow on the top side.

0143 and 0144 are secondary 02 sensor codes. Interesting.

Originally Posted by smolck

0143 and 0144 are secondary 02 sensor codes. Interesting.

Secondary? Secondary to 0171 and 0174?

Hi BROOKSBC i have the exactly same problem with the same car, the same codes and change some of the same parts that you mention, and still can't fix it. can u please tell me if you find what the problem is? thanks

What were the code meanings aside of the numbers that your code reader or obd scanner gave you.

Originally Posted by BROOKSBC

Secondary? Secondary to 0171 and 0174?

Were you ever able to diagnose the problem?

I had been having these same problems for awhile and when my mechanic smoked the engine, the leak was at the oil cap! So, $20 later (dealer price), problem fixed. Then I searched for "oil cap replacement" on here and found no threads mentioning leaks from, or replacing oil caps. It may be a widely overlooked problem.

Read post #17

Yep, never searched E46Fanatics about it...and there it is. Saving that post too, lots of good info there. Thanks!