TDI Major Issues

My brother has a 1999 Jetta TDI 1.9T with 95,000 miles on it..

Heres where the issues start..Ever since he bought it back when it had 88,000 miles..It skipped at idle for some unknown reason..Not all the time but it sure does idle rough ..But as soon as you step on the throttle at all it clears right up and runs the way it should..but if you slow down and stop for a stop sign it skips even when its fully warmed up..Go Figure..Air and Fuel filters are clean...It doesnt seem to lack any power..it only skips when you start it and it idles but if you rev it up at all it will come right out of it..when it idles back down it starts skipping again...Its beyond me...I know there is an issue with the timing chains but it was changed right before he bought it...


Second issue.. Up here in Northern Maine we have been getting some cold spells recently and if it gets below 10F Degrees or colder it will start up and run fine but after you drive say 10 miles it dies..The only way to get it running is to change the fuel filters and she will run good again but if it gets extreamly cold again it will die..We changed it one night and he continued on his way and when he left the place he was at..it died no more than 5 miles down the road..it was 2 degrees out..Very cold..But the Jetta has winter fuel in it...It uses the same fuel my Fathers Gmc Duramax pickup uses and My Fathers truck has had no issues whatsoever...Its died like this 6 times so far..and only when it gets extreamly cold..We've added all kinds of Attitives to the fuel and it still dies....Go Figure...It will bog out and loose power and shut off and it will not start up unless you change the filter and then it will only go 5 miles or so down the road and it'll do the same thing...

I'm really confused about whats bothing it...I've never seen a diesel act this rediculas in the cold weather...

Any help would be great..He wants to just get rid of the car "He's not very mechanicly inclined" I'm not very familer with the Volkswagens..So I dont know what to really look for besides changing filters...

Is this 1999 an A3 or an A4 car? The A3 is more boxy and angular and the A4 is more rounded and refined looking. If it's an A4, look for the thread titled "Fuel gelled X3". It has a good explanation of what may be happening.

whitedog said:

Is this 1999 an A3 or an A4 car? The A3 is more boxy and angular and the A4 is more rounded and refined looking. If it's an A4, look for the thread titled "Fuel gelled X3". It has a good explanation of what may be happening.

Click to expand...

Its the A4

OK, just for future reference, remember that it's actually a 1999.5. Or an A4. Either one will help people help you.

So read on about fuel sending units...

I'd adapt the injection quantity to take care of the slow down shudder, and check the timing for the starting issues.

if not jelling probably injection pump failing

First, I really have to recommend the trusted mechanics for these cars. There is someone located in Richmond, Maine, but I don't know how far that is from you. These mechanics specialize in TDI's, and often are able to sort things out very quickly, saving you lots of hair pulling.

You might want to check out a few things pretty easily first:

Problem #1: Sounds like it could be something called "slow-down shudder." The ECU can sometimes inject too much fuel at idle, causing it to be rough...has the vehicle had any fuel delivery work or modifications? You can often fix the problem easily with software. Find someone with VAG-COM software here, and check out the IQ.

Since you've checked the filter and they're clean, you might check for other obstructions...the CCV can cause oil to pool in the intercooler. You could try draining it by pulling the lower hose off. (I think this is less likely than the IQ adjustment)

Problem #2 might be gelling or water freezing somewhere in the fuel system (filter or sending unit). Check out this thread...this guy is having some similar problems.

Hope this helps you out! Don't get rid of the car yet!

Herm Pasker is one of the good guys. Hermtdi... He's in your part of the world.

running rough & stalls

When was timing belt done? Have you had the car scanned for codes? What kind of air filter, stock? Have you tried unplugging MAF? Are there any leaks around IP? Pull out fuel pickup in tank & see if it is clogged.

I agree; shudder and gelling. Shudder is really a non-issue but can be adjusted away. Gelling suggests an anti fuel additive and/or removing obstructions in the fuel path (drilling the fuel pick-up).