Hopefully one of you guys will be able to help with some advice.

I've got a MkIV Golf 25th Anniversary with the PD150 TDI engine and roughly 150k on the clock.

All has been well with it until today when a vibration and horrendous rattle developed from under the bonnet. I pulled over, stopped the engine and popped the bonnet ... nothing untoward to be seen. Started the engine again and slowly applied power ... more rattling and further throttle application and the engine tries to jump off its mounts.

I managed to drive home with partial throttle (1500rpm and under) and puffs of dark grey smoke associated with any throttle application, gearchange was smooth, turbo seems to be boosting OK too.

Any clues? Is it the dreaded DMF failure? Would that explain all the symptoms including the rattle and smoke?

Hope someone can point me in the right direction!

It won't be a DMF causing smoke. Probably a fuelling/timing problem. Time to get it on VAG-COM.

I suspect a leaky boost hose, but cannot be sure. Would need vagcom to read what the ECU thinks is wrong and go from there.

Big end gone!!

What i should have said is that it doesn't rattle all the time ..... it's running on all four cylinders, doesn't smoke all of the time (only slightly on acceleration) and the turbo is boosting OK too.

If it was big end I think it would be a terminal knocking noise?

.... and it runs smoothly except when revving past 1500rpm.

The rattle is quite metallic and the engine unbalance only comes in at 2500rpm (ish)

Remove the rocker cover and check the camshaft and followers for wear, it is becoming a common fault on the 150pd's.

Have a look here for more infomation and photos:

Chocolate PD cams strike again - Why can't I just get chocolate eggs instead! - uk-mkivs

Does it rattle more or less with clutch either in or out? If it's the same regardless of clutch position, you can rule out the DMF. I would suggest looking at top-end wear as well - 150k miles is a fair old amount of miles and they are known to wear the cam & followers.

I will have a look today ..... funnily enough I was thinking that one thing I hadn't done was dip the clutch when the engine was rattling.

However, I think the noise is quite tinny and top-end so a boogered cam/lifters might well be a possibility ..... if it is and I have got to just shy of 150k I've done well or so it seems from other people's experiences.

Look up the map of helpful Brisk members with vagcom - hopefully you'll find someone local to you.

Do a scan and hopefully this will shed some light.

Also if you unplug the MAF and it runs better - then it's a dead MAF. Apparently they can fail gradually or suddenly. If unplugging the MAF gives you back a normal engine (with a weaker top-end) then it's deffo that that needs changing. You can run for a while with an unplugged MAF on a derv apparently.

HTH

Bas

when a DMF fails it can cause all sorts of problems , misfires and poor running is one and obviously metallic knocking is the other main one , so don't dismiss that as the cause of your problems

Evening everyone.

Correct me if I'm wrong but is there supposed to be a small (10mm diameter ish) rod sticking through the top of the lifter??

If you look dead centre in the photos you will see what I mean .... just to the right of the valve spring.

Is there a decent aftermarket cam (& decent hardened lifters) that can be bought or am I best to stick with VAG OE?

My car has nearly done 150k so guess I am lucky!

Oddly enough I was just going to say the camshaft and lifters are going to be shot.

Very common issue on the ARL engine, the camshaft bucket wears out and the centre pops through wrecking the camshaft.

Not a cheap repair sadly, done a fair few of them.