AJM misfire and top end rattle.

[Yarrum]

My 2001 A4, 1.9tdi has ran without major drama for 165,000 miles helped I believe by my sympathetic driving and oil and filter changes every 5-6,000 miles using Quantum oil and Audi or Mann filters.

Earlier in the week Mrs Yarrum was using the car to commute and reported that it 'was sounding a little rough'.

I used the car for commuting today and, as usual it started first turn of the key at 0530 hrs with an outside temperature of -4 degrees.

The engine was however a little rough and seemed to be misfiring slightly, with a stronger than normal whiff of unburnt fuel from the exhaust and a slight 'tappety' rattle.

I drove carefully to work and apart from a little roughness there was no major drama or lack of power. This afternoon, I poured in a bottle of Forte engine flush, hoping more than anything that a tappet was maybe gunged up. I arrived home (after 25 miles) and the misfire is still there, and varies in intensity from a slight 'miss' to a full scale shudder which has the engine dancing around on its' mountings although the idle speed remains normal at 800 rpm. According to the trip computer the car is still getting 57mpg and there are no warning lights on the dash.

I took off the rocker cover half hoping to find something loose or broken but all appears normal with no serious wear on the cam lobes or rollers.

Starting the engine up with the rocker cover off (covers the engine bay in oil) and confirms there is a definate 'hard' metallic ticking from the 'top end' .

Has anyone had a similar problem or have any ideas where to start looking ( ie camshaft, followers, valves fuel pump timing or injectors) before I break out the spanners and start to strip off the head.

[STEWY L]

sounds like an injector is putting too much in,causing a diesel knock to me.
it would have to be a mechanical failure of the injector i suppose,or you would have a light on
i suspect,
regards,
stewy.

[Yarrum]

Cheers for the starter Stewy!

Any idea how to identify which injector, or is it a case of pulling them all out and checking individually?

[zollaf]

buy and fit a new injector harness. if you could get a fault code read, you will probably have the code (whatever it is, can't remember) relating to a misfire on no. 1 cylinder. this would confirm its more than likely the injector harness. they are £50 or so from vw, and will take you an hour or so to fit.

[Yarrum]

Cheers zollaf for that heads up.
I will tow the car to my local independant VW/Audi chap and see what his 'puter turns up. Fingers crossed a £50.00 harness fixes it as opposed to £180.00 or so for a new injector (with the likliehood I will probably need 4 )