28B8 code solved

[bigwinn]

Posting for future reference

A mate had 28B8 showing which wouldn’t clear. Idle was iffy and engine stumbling.

28B8 shows as mechanical stiffness in vanos exhaust side (or similar)

Changing the exhaust position sensor did nothing
Swapping for a different exhaust sensor did nothing too

A further Google suggested swapping out the piston that sits inside the vanos unit once the solenoid is removed- you can feel it with your finger

That was stiff to depress

Swapped for another spare unit and the code so far has not returned

Success I hope

 

[enuff_zed]

Ah, so that's the M54 engine then?
Yes I've had a couple of those.
First one was on Vall's 2.5i. Tbh, I kept the original shuttle valve, but took it out and lightly cleaned the oil varnish off it with a softish emery cloth.

Wish you'd mentioned it! I could have saved you some faffing about.

I now make sure that whenever I do a vanos seal overhaul, that I also remove both inlet and exhaust shuttle valves and clean them up too.
Much easier on the bench.
I also do a quick functional test of the solenoids while I'm at it.

 

[bigwinn]

Ah, so that's the M54 engine then?
Yes I've had a couple of those.
First one was on Vall's 2.5i. Tbh, I kept the original shuttle valve, but took it out and lightly cleaned the oil varnish off it with a softish emery cloth.

Wish you'd mentioned it! I could have saved you some faffing about.

I now make sure that whenever I do a vanos seal overhaul, that I also remove both inlet and exhaust shuttle valves and clean them up too.
Much easier on the bench.
I also do a quick functional test of the solenoids while I'm at it.

What is the shuttle made out of?

We couldn’t work out if it was a very light metal of some sort- but there was minimal heat expansion as I was working on a hot engine??

 

[enuff_zed]

I think it’s metal but possibly just a light alloy?