80 TDI running rough

Bandwidth Buster Joined: Sep 09, 2008 Posts: 552

Just bought an 80 tdi as a daily runner. It isn't too well. It shuddered on the way home in 4th and 5th until the speedo stopped working. Idle is a bit rough and sometimes the revs hold for about a second when you lift off the throttle.

I scanned it on vagcom and got the following codes:

When I cleared them and ran the car only one came back - 00777. I think the MAF was me as I ran it without the MAF connected yesterday to see if it made any difference.

Injection quantity is all over the place at idle too, jumps from 1.2 to 3.4 (which is too low).

Anyone any ideas where to start?

Oh, and the speedo started working today and the shuddering came back

Confused

Site Moderator Joined: Jan 31, 2003 Posts: 9144

This is a drive by wire job I think so you don't have a throttle cable.

I always thought the throttle sensor was above the pedal but could be wrong

Bandwidth Buster Joined: Sep 09, 2008 Posts: 552

It is at the pedal. If it was dodgy it would explain why the revs stay high for a sec before dropping when you lift off. Think I'll replace it and the speed sensor at the gearbox.

UltraUser Joined: Mar 18, 2005 Posts: 1570 Location: Gwent

I think the key to this, is the juddering and the speedo operation. There is a fairly common problem with the judder and one of the 'band aid' fixes is to snip a blue and white wire which goes to the ecu from the speedo.
This will cause a 'harsher' throttle sensitivity, but should clear the judder. Before you do this, try unplugging the sensor, to see if you can live with it? The full fix is to strip down the injector pump, which will likely be contaminated with metal particles causing mayhem, or change the pump.

this thread has a solution http://www.vwaudiforum.co.uk/forum/showthread.php?105235-TDI-Judder-quot-Solved-quot&highlight=judder%2A

and this one has the details:

http://www.vwaudiforum.co.uk/forum/showthread.php?12393-Audi-80-tdi-juddering-bucking-jerking/page26&highlight=judder%2A

Bandwidth Buster Joined: Sep 09, 2008 Posts: 552

Cheers, I sent the top section of the pump away to someone who has stripped and cleaned many of these pumps. I hope to get it back tomorrow. Fingers crossed that it fixes the issues. I bought a spares car too,it has the same running issues so I may take a brave pill and have a go at the pump myself.

My day has one as well with the same problems, it would be handy to be able to fix them myself.

Bandwidth Buster Joined: Sep 09, 2008 Posts: 552

The car seems to be sorted now, I got the top section of the pump back yesterday and fitted it this afternoon. After a bit of fiddling to get the IQ set it seems to be running really well now. No grunting at idle now and able to sit in 5th at 1200rpm with no juddering.

Now just have to work out if I'm brave enough to take my spare pump apart and clean it myself Confused

UltraUser Joined: Mar 18, 2005 Posts: 1570 Location: Gwent

Good result!