1.9 TDI Audi 80 is sluggish and smokey

[Spathodus77]

Hi,

Please can someone help confirm my diagnosis of a problem...

Last week I picked up an Audi 80 1.9TDI and on the 40 mile trip home I found that it was leaving a big cloud of black smoke behind whenever I was accelerating, and when I was accelerating (particularly in 3rd , 4th or 5th) that the car could n't decide if it wanted to pick up speed or not. It would climb 200rpm then feel sluggish for half a second then pick up another 200rpm then feel sluggish etc.

At first I figured that the car needed a service so changed the air filter, oil, oil filter and fuel filter. I also filled the fuel filter with injector cleaner and gave the car a good hammer down dual carriage (high revs, not speed!). This may have made some small improvement, but the air temperature has also dropped which I suspect is the true reason for the improvement. The car idles fine at 800rpm and there are no untoward noises from the engine bay when revved stationary or on the move.

Today I disconnected the mass air flow sensor and drove the car a few miles. The lumpy acceleration and smoky exhaust were cured, although the cars performance is pretty low with the sensor disconnected (max 65mph in 4th - about 3000rpm). Based on this evidence I reckon that the mass flow sensor is at fault. What do others think?

Before I replace the sensor I am going to try giving the electrical contacts a clean and I'd also like to give the sensor a clean. Is this possible? I would plan to give it a good spray with electrical contact cleaner (or brake cleaner) - is this likely to be successful?

Given that disconnecting the sensor has made an improvement can I rule out an injector or ECU issue as the cause?

Thanks,

Ralph

PS: not sure its related but the cars engine temp gauge has never read higher than 60ºC...

[JKY]

Double check that low temp issue before you spend on the air sensor.
If it is genuinely only running at 60degrees then that could be the problem.
Could be bad thermostat or if it is getting hot then faulty sensor.

[cptsideways]

I did'nt think the pumps were temp dependent on these??

Airflow meter would be my guess, some good ones on ebay via the airflowmeter company, transformmed a few cars I've owned.

[TooLateForAName]

I'd also be having a good luck at all the induction pipework/ducting for splits/holes.

[warmfuzzies]

Sounds like the turbo hosing, or turbo/wastegate to me, had almost the identicle issue when I forgot to replace the hoses after I took the intercooler to bits.

k

[GreatGranny]

I've just had the boost pipe on my 03 Alhambra TDi reconnected as it popped off last night.

The performance dropped a huge amount with very jerky delivery and it had trouble getting to 30mph.

Sounds like something similar but maybe a leak/split pipe.

[NBirkitt]

Similar problem on my '94 80 TDI was due to a split in the underside of the short hose between intercooler and turbo, right on top of the engine, just to the left of the oil filler cap. It must have started off as a slight crack and then grew to the stage that it was opening up like a valve under load/ boost and losing all the airflow to match the fuel delivery = big cloud of smoke! Not obvious at first inspection or at idle, but undo the two clips and pull the hose off (easy) and have a close look. Careful, it will be very mucky inside – best wear latex gloves and have a rag handy!

Edited by NBirkitt on Friday 12th February 18:31

[Tame Technician]

As suggested check for a boost leak, but TBH there a bit to old for me to know.

Has someone messed with the pump timing, done the belt wrong
(its got one of those old truck pumps hasnt it?)

[Spathodus77]

Thanks to all for your suggestions. I took the mass air flow meter off, prised off one of the protective grills and gave it a good spray with electrical contact cleaner - No improvement. The weather was warmer today and the problem was particularly prevalent. I'II check the air hoses as suggested because it is easy and free .

If no solution can be found this way I shall certainly be booking the car into an indie to have the temp gauge issue checked out.

Ralph

[Spathodus77]

Turns out the problem was a 2 inch hole in the inlet tubing between the intercooler and the inlet manifold. Managed to get out at the weekend and fit a new tube. Now running lovely.

Thanks again to all for putting me on the right track.

Ralph.