Rough idle after Rocker Gasket change (e39)

[cliffdunedin 8]

Hey guys. Did the RCG change yesterday which should have been pretty straight forward but stripped one of the cover bolts i put it all back together and tightened the stripped bolt as tight as I can.

Once started it was immediately trying to stall and would have without some accelerator, after a couple of revs it seemed to sit at about 600rpm ok but still not feeling or sounding right, I took it for a good 10 min run and all was well no lack of power/noises/vibrations etc but at lower revs it came back. I returned home and gave it a scan and nothing came up. I checked all the Rocker cover ground wires, Coil packs, AFM, couldn't find any air leaks, ICV has been cleaned in the last year or so.

Edit: I also cleaned and scraped the rocker cover while it was off and have noticed that when the accelerator is lifted it slows qicker than normal.

Does anyone have any ideas what this issue could be? Cheers heaps

Edited December 7, 2014 by cliffdunedin

[Arma 134]

Have you had a look at the CCV valve? Some symptoms seem to align with that going bad from what I've read, but don't take my word for it I'm not a mechanic.

Another silly suggestion: by accident some oil couldn't have gone into the plugs during the RCG change right?

[charles28 136]

The Valve covers are crap plastic and crack if you try and tighten the bolts much over 7 foot pounds.

Its likely a vacuum leak.

Did you put Sealant on the 1/2 Circle bits?

[jeffbebe 1559]

Plastic valve covers??? Eh?? There is a cosmetic plastic cover but the actual valve cover is magnesium alloy (which is why they oxidise badly). You can overtightened the bolts and split the rubber grommets though which could cause a leak.

[cliffdunedin 8]

Have you had a look at the CCV valve? Some symptoms seem to align with that going bad from what I've read, but don't take my word for it I'm not a mechanic.

Another silly suggestion: by accident some oil couldn't have gone into the plugs during the RCG change right?

Yeah you're right, the symptoms do sound similar but i don't think i could have done anything to upset the CCV during a RCG change.

The Valve covers are crap plastic and crack if you try and tighten the bolts much over 7 foot pounds.

Its likely a vacuum leak.

Did you put Sealant on the 1/2 Circle bits?

Plastic valve covers??? Eh?? There is a cosmetic plastic cover but the actual valve cover is magnesium alloy (which is why they oxidise badly). You can overtightened the bolts and split the rubber grommets though which could cause a leak.

The cover does feel like plastic but i'm fairly sure i didn't damage the cover. i put gasket seal on the half circle bits, the rubber grommets are new as well.

Could a leak around these areas cause this issue? It never changed the idle much if i opened the oil cap while it was running before so assumed that wouldn't be a problem.

[Ahmedsinc 414]

Plastic valve covers??? Eh?? There is a cosmetic plastic cover but the actual valve cover is magnesium alloy (which is why they oxidise badly). You can overtightened the bolts and split the rubber grommets though which could cause a leak.

Yeah mate, they're plastic from the M52TU onwards. Bloody terrible idea, they warp as they age, rendering the valve cover gasket mostly useless. Hooray for mandatory use of recycled plastic - thanks, EU!!

[charles28 136]

Plastic valve covers??? Eh?? There is a cosmetic plastic cover but the actual valve cover is magnesium alloy (which is why they oxidise badly). You can overtightened the bolts and split the rubber grommets though which could cause a leak.

Yes the actual valve cover is plastic, its a silly design.

I had to buy a brand new one at a cost of $500 as mine was warped.

[jeffbebe 1559]

Ridiculous.

[B.M.W Ltd 950]

Ridiculous.

That is the price for a new one from BMW

[jeffbebe 1559]

That is the price for a new one from BMW

I meant the plastic not the price TBH, Glenn!!

[charles28 136]

I meant the plastic not the price TBH, Glenn!!

Its quite common on newer cars.

Even the old Mk3 Golf VR6 has a plastic valve cover, (which I removed today due to the useless plastic timing chain guide breaking, which then caused the chain to jump a tooth or too resulting in the engine sounding like:

Yes.. cars come with plastic timing chain guides too sometimes, what a clever idea.

Basically.. the plastic parts are always the first to cause issues with any euro car i've owned.. whether it be the cooling system, valve cover..oil separation valve and associated hoses.. a lot of the rubber parts also become hard and stock working correctly, but i suspect a lot of newer japanese cars now feature a lot of the same plastics.

I have replaced ALL of these items on my E39 now. (not the timing chain guides, not sure if they are even plastic on the E39 530i)

Edited December 8, 2014 by Charles32

[jeffbebe 1559]

Not sure about the 530i but they're plastic on the 540i... Go figure. Still, if they built them too well nobody would need a new one.

[Ahmedsinc 414]

I have replaced ALL of these items on my E39 now. (not the timing chain guides, not sure if they are even plastic on the E39 530i)

Man have I got bad news for you mate - chain guides are plastic too. Got a B30 in the shed with it's head off, M50 is the same.