CarTalk.com Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

2006 BMW 3 Series - Idle issues

I have problems with the idling,I thought it was a broken hose,but everything looks normal,a friend of mine did a compression test on all cylinders and cylinder #6 only gave us 50 in pressure,he thinks is a blown head gasket,I just want to confirm if this could be the problem?

I suppose you could use a bore scope to look inside, but doubt if you could see if the low compression is caused by a valve or ring. Head will have to come off regardless of the cause.

3 Likes

It could be a blown head gasket. Often a blown head gasket will result in two adjacent cylinders having a low compression, so just one being low would make me want to do some more testing before assuming that. It could be a sticking valve affecting only number 6 for example, and there might be a way to unstick it without removing the head. Is this a direct injection engine? Turbo?

Do a leak down test on that cylinder.

At least you’ll know why that cylinder has low compression.

Tester

1 Like

Could be coked up rings due to a faulty injector, so many possibilities!

I can neither confirm nor deny that over the internet. Tell your friend to confirm it, rather than other thing that will cause low compression. Not that any of them are cheap tp fix either.

The #6 cylinder is at the end of the block, no? So there could be a head gasket problem that would only affect the one cylinder. That said, I agree that more diagnosis is required.

Thanks for your imput,I will do some more testing.