E39 intermittent engine knocking sound/vibration

[jeffbebe 1559]

It's a 528i with an M52 engine. Every now and again (rarely) the car starts shuddering with an unpleasant knocking sound. It's only happened two or three times and the circumstances have all been different - though the car's always been warm when it's happened so it's not a cold start issue. Has been at a variety of speeds from virtual standstill (when it sounds worse) up to about 60kms where it's present but not overwhelming. Doesn't seem to lose power, at least not significantly, when the shudder starts up.

It happened recently and I found the o-ring around the dipstick had split and was leaking oil - I thought that might be the problem - but it happened again today. Other than that the engine's mint - I've done heaps of stuff on it in the last few months to get it up to scratch.

As it happens rarely I figure that it's unlikely to be a vacuum leak which would cause it to happen all the time.

Replaced all the ignition coils so it can't be that and all the hoses are in good nick as far as I can tell.

I wondered whether vanos or injector seals might be failing but figured it would be more likely to happen when cold rather than running temp.

Any ideas?

Edited November 8, 2012 by jeffbebe

[KwS 2391]

random shot, but checked you dont have a loose spark plug or something silly?

[*Glenn* 854]

Get it scanned... it's possibly a camshaft position sensor

[jeffbebe 1559]

Get it scanned... it's possibly a camshaft position sensor

Scanned it the first time it happened - when I found the broken o-ring on the dipstick - and n faults, but will get it scanned again.

A mate suggested to me it might be a failing fuel pump. Does that sound likely?

[jeffbebe 1559]

random shot, but checked you dont have a loose spark plug or something silly?

Something silly is the first place I start, otherwise my mechanic thinks I'm a dullard when I bring it in! So yes, checked all the obvious.

[jeffbebe 1559]

So she's in the shop. The vibration came on today and big loss of power... This time it didn't go away - running on only 5 cylinders. It's got brand new ignition coils so shouldn't be those. Took it to my mechanic for scanning and hopefully sorting but too late in the day to do anything, so she'll be holidaying there over the weekend while I drive around in a courtesy one of these...

Choice

[allan 295]

The E39 is getting it's revenge beware At least you did the right thing and got it to your mechanic to have a look at it. Let us know what the problem was?

[Allanw 1065]

AH HAHAHAHAHAHAHA!

You poor, poor boy!

Don't brake too hard, in case it tips over forwards! Becareful on carners. Don't pull out in front of anyone.

Actually, just stay home

Hope they get your car sorted soon. REALLY soon.

[jeffbebe 1559]

The E39 is getting it's revenge beware

Revenge for what? I've been nothing but kind to my E39! What will it do if I'm ever unkind to it!! haha

[jeffbebe 1559]

Hmmnn. Feel a bit of an idiot. Turns out that one of the brand new ignition coils that I put in just a few months ago has failed. Guess I should have checked more thoroughly but I just assumed they'd be okay as they were new.

Not happy, as I'm now worried that the other five I bought might be sh*te as well. Got them new from the US so will be looking for a refund. Will let you know how I get on. Fortunately, they were relatively cheap... you get what you pay for, I suppose.

[Allanw 1065]

Hmmm... yeah, you can't always rely on new parts... bummer.

They'll probably want the stuffed one shipped back though

The ones Paul from Milland has on trademe are pretty cheap too.

Edited November 12, 2012 by Allanw

[jeffbebe 1559]

Hmmm... yeah, you can't always rely on new parts... bummer.

They'll probably want the stuffed on shipped back though

The ones Paul from Milland has on trademe are pretty cheap too.

Got a new one from Gavin at Euro Italia. Guess if they replace the b*ggered one I can keep it as a spare in case any more go! Fingers crossed it was just an unlucky dud and the rest are all sweet.

[Allanw 1065]

Fingers crossed it was just an unlucky dud and the rest are all sweet.

Probably is just one dodgy one.

If nothing else, you can be thankful the loan "car" is no longer in your possesion