Sudden Power Loss - Lumpy Idle

[Yangi19]

Evening everyone

just got home after being recovered by AA (this time very good service and under 2hrs from 1st call to back of truck!)

So I have major problem and would be useful to know if anybody else had similar

The Car:
A6 Allroad 4B C5 AKE 2.5TDi 2003 with 180k. (cam belt at 150k - fuel filter - Steering Pump - Alternator approx 8k ago)

Scenario:
Car been running well with no 'mechanical' issues for a good while. Then today, cruising on M25 at a full 70mph/Half Throttle (a rare bonus on M25) and in lane 3 overtaking lane 2 .....with nothing in lane 1!!!!!!!!!!! when I just felt something different - either engine note or small vibration or both. I am very mechanically sympathetic and generally notice if something 'different' straight away!

I was 1 mile from Clackett Lane, so pulled over to come off at Services and noticed lack of response from throttle/lack of power. Stopped at Services with engine running and it was Lumpy as **** on Idle. Not Rattling - apart from Idling on 4 or 5 cylinders and No Smoke. And cant do much about it there, so decided if was running would try get back home rather than get stuck at Clackett Lane!!.

Pulling back onto M25 was a mission as had no power at all, but got up to 50mph and decided that was sufficient. carried on at 50 to M26 and was fine until came to incline where speed dropped to 40-35 followed by some smoke for a short while (dark but not black) by time had done another 5 miles to next junction engine had zero power and if I gave any throttle was smoking again - but would idle at NORMAL revs although still Lumpy as ****. Had to queue at roundabout but managed to get to layby just the otherside by just letting car drive itself on tickover.

Engine stills starts 1st time
Lumpy tick Over but still idles at 800rpm
Revs up slowly and after a moment rattles and smokes a bit (not LOTS)

.......... 25 Miles/35mins before this problem occurred, I had filled up with 58 litres of Shell 'normal' Diesel at Cobham Services. ( I only EVER use Shell Diesel now after having many issues with a previous car on supermarket fuels.........)

NO ENGINE MANAGEMENT LIGHTS ON CAR.... NO LIMP MODE NOTHING! ALL NORMAL.

I will get Diagnostic tool on car in next few days, as I suspect Injectors are going down 1 by 1?

I may be wrong... that's why any of your previous experiences would be good to know ????

[Crasher]

Take the cam covers off and check for cam wear and possible ejection into the head of cam fingers due to massive wear.

[Amphitryon]

Take the cam covers off and check for cam wear and possible ejection into the head of cam fingers due to massive wear.

The wear in those pictures looks very high. Would you expect that kind of wear from high mileage alone or does it indicate oil starvation? Thinking of which, how are the camshaft and those fingers oiled? Years ago I had a Ford with an OHC engine which had a pipe with holes in above the camshaft. It was a known issue for the holes in the pipe to block so it was a service check to remove the cover and check that they were all delivering oil.

[Crasher]

That was a mild one, on my junior school teachers A4 quattro with 80k and full service history, quite a few years ago as he has an A4 Allroad now. The problem is modern oil is rubbish on direct wiping surfaces which is why just after your car was made they switched to roller fingers. One A4 quattro I did many years ago had so much wear (4 years old) that the valve stem tops were worn down almost to the locks and if I remember well, four fingers just lying there in the head having been ejected, it wasn’t until two from one cylinders inlet came out that he realised there was a problem. I had to fit two new genuine heads and surprise surprise these are upgraded to the roller version. If you fit a cam kit, use a ZDDP oil additive at each oil change to help protect wiping surfaces. Fitting the later heads would now be far more than the car is worth.

[Yangi19]

Thanks for the response Crasher
But do you think that worn Cams/Fingers would cause a Sudden issue when everything been okay up to then... or rather something that develops more slowly over time?
Cheers

[Yangi19]

Borrowed Diag tool earlier and 2 Faults registered on Engine Management:

01375 - Engine Mounting valve - Stage 1 .... Short to Plus (seen that before) not caused issue.
00575 - Intake Manifold Pressure ....Impluasable Signal.

Had a few 'Implausable signals' in past on Throttle and stuff / cleared and found it not returned. cleared that, started Car... runs like *****, but 00575 did not reappear.

Diag tool wonderful.... IF YOU KNOW EXACTLY WHAT YOU LOOKING AT/FOR LOL

No obvious Air Leaks/vacuum issues
No obvious Diesel Leaks

Disconnected Sensor on Intake (MAF I Guess) when engine running.... made No Difference.

Started Engine with MAF disconnected.... Made No difference.

....... SO next question is , HOW DOES INJECTION SYSTEM WORK? Different to what I have been used to before (common Rail, individual plugged Injectors....)

But Audi has 6 cylinders / injectors fed from Central Control Unit by look of things ? Is that correct? If so.... How the F*** do you start looking for individual cylinder issues???

OHHHHH MYYYYYYYY

[Amphitryon]

On the injection, I did find an article on three types. The oldest, which sounds like the system you describe and seems to match my 2001 AKE, has a single, high pressure pump/distributor and individual high pressure steel pipes to each injectior. Next in age was PD with low pressure feeds to each injector which has ain internal mini pump driven by an extra lobe on the camshaft to achieve injection pressure. Newest was common rail.

I also can't think of how you would disable one cylinder at a time to see if it was contributing anything useful.

I also looked up the 2nd fault code and maybe it is worth not writing it off so quickly just because it didn't immediately come back. See 00575 - Ross-Tech Wiki. Maybe it would only be relogged under load?

[Crasher]

It is a Bosch VP44, a VEP "Verteilereinspritzpumpe" or distributor injection pump.

The reason cam wear can cause a sudden loss in power is a pair of followers on one cylinder being thrown out. One could have been out for a long time, in fact each cylinder could lose two and you would barely notice but if a pair of inlets come out they misfire, if a pair of exhausts come out they run like **** and soon lock up due to diesel being injected but not ejected!

[Yangi19]

On the injection, I did find an article on three types. The oldest, which sounds like the system you describe and seems to match my 2001 AKE, has a single, high pressure pump/distributor and individual high pressure steel pipes to each injectior. Next in age was PD with low pressure feeds to each injector which has ain internal mini pump driven by an extra lobe on the camshaft to achieve injection pressure. Newest was common rail.

I also can't think of how you would disable one cylinder at a time to see if it was contributing anything useful.

I also looked up the 2nd fault code and maybe it is worth not writing it off so quickly just because it didn't immediately come back. See 00575 - Ross-Tech Wiki. Maybe it would only be relogged under load?

Many Thanks Amphityon for taking the time to reply

I can only think of cracking off the injector pipes a little at the cylinders to see if any difference (messy - but basic I guess)

Will investigate the comments on Ross tech stuff too.

Many Thanks
Yangi19

[Yangi19]

It is a Bosch VP44, a VEP "Verteilereinspritzpumpe" or distributor injection pump.

The reason cam wear can cause a sudden loss in power is a pair of followers on one cylinder being thrown out. One could have been out for a long time, in fact each cylinder could lose two and you would barely notice but if a pair of inlets come out they misfire, if a pair of exhausts come out they run like **** and soon lock up due to diesel being injected but not ejected!

Ahhhh, I see.
Will Investigate further
Many Thanks