TDIClub Forums

TDIClub Forums (
-   VW B5 Passat TDIs (
-   -   Rough idle question, 2005 Passat TDI (

lynnejohn July 31st, 2012 20:53

Rough idle question, 2005 Passat TDI
Got up this morning and the wagon started up with a very erratic idle. Not just a single cylinder missing but seemed like random misses for 30 seconds or so. I little fuel seemed to help a lot, but the idle symptom did not go away until the engine was warm. When I went to lunch and started the car, the idle missed a little but not as much as the morning. Some notes on the car:

- Recently had the BSM upgrade and Mike at M&M Auto said the cam looked ok.
- No leaking of fuel and I don't hear any excess noise (hissing) from the engine.
- Fuel filter changed.
- No engine codes.

After reading some amount on the subject I'm hoping for a cracked hose or maybe MAF.

Suggestions on what I might be able to check next ?


DezlDan August 1st, 2012 00:22

What was the torsion value set to? Mine was set to 2 during by BSM upgrade and the car idled poorly. I had them set it to 0, where it should be, and it now idles and runs great.

lynnejohn August 1st, 2012 08:20

I could find out but I've had the car 3 weeks since the upgrade and the issue did not appear until yesterday (the car has had an occasional "miss" when running on the highway under load, but this I've noticed since I bought the car.) Also this is when the car is in park (not an axle problem.)
This morning when I started the car the idle was rough and even when I gave it a little throttle the engine was still not smooth.

sirpuddingfoot August 1st, 2012 13:34

Definitely sounds like a timing problem. I'd get it checked sooner than later.
Since you opened the fuel system, there could be air sneaking in at the filter too, but I'd expect you'd see fuel leaking around there as well.

"Missing" on the highway is something we experienced with a dirty old fuel filter (usually cruise control on a level stretch).

So: get timing checked, then check your fuel filter hose connections. You could consider a diesel purge treatment as well (make sure to follow the PD instructions).

lynnejohn August 1st, 2012 15:05

I guess my MAF line of thinking was due to the sudden onset of the problem and that it had not been as severe in the
several starts since then (I also have a vague recollection about Jetta's and MAF problems.) I'll check the fuel filter
lines tonight.


thundershorts August 2nd, 2012 06:07

I'll bet on the timing being a bit retarded.

lynnejohn August 2nd, 2012 10:44


Originally Posted by thundershorts (Post 3887598)
I'll bet on the timing being a bit retarded.

So I should have this checked by my local shop? When the BSM was done it got the new timing belt, so I had not thought about timing.
Is there a chance that now that the gears on the BSM have worn in a little (6K) things could be off slightly?

lynnejohn August 15th, 2012 19:20

So I took the car in and guess what, The tech can't reproduce the rough idle problem. He notes no misfires and took the vehicle for a test drive (once the car is warm it idles fine.) The tech checked the fuel injection timing and said it was good (MVP 13+23 ??) He then wanted to check coding and software level of ECM. At that point the care has a Malone tune and it had the problem before the tune.
Should he have been looking at the ECM at this point instead of maybe vacuum hoses?
I'm out $70 but the timing has been checked. Is there a simple way to narrow possible problems, or should I put the original ECM code back in and let them go from there?


thundershorts August 15th, 2012 20:51

doesn't sound like the torsion value was checked. you might ask why it wasn't or perhaps you didn't ask specifically what the torsion value was set to.

2002tdi August 16th, 2012 08:49

mine has been doing this for quite some time. i was thinking possibly a diry intake manifold. or a fuel injector just slightly plugged or dirty. as soon as it warms all the way up to operating temp it goes away. i have learned to just deal with it. let me know what u come up with .

oilhammer August 16th, 2012 08:56

Sometimes a tiny leak at the fuel filter thermo-T o-ring can cause some air pocket and a rough startup. Even ones that do not appear to have any external fuel leak.

lynnejohn August 16th, 2012 20:46

Ok here is my next few steps:
- Run the Diesel Purge to clean the injectors.
- Have the torsion value checked (according to Mike at M&M, this should not take long.)
Oilhammer - Could I simply pull the T o-ring before start-up to see if there is an air pocket at the top of the filter?
One last thing I'll mention is that when I was changing the fuel filter I pulled the fuel line closest to the front of the car (not the T connector) and
a small piece of what appeared to be the hard skin of a corn kernel dribbled out with the fuel. It was the first time that I had ever seen anything come out of the fuel line other than diesel. The picture is not great but you can see it is slightly smaller that the tip of the pencil and was kind of hard (it broke into smaller pieces when I crushed it.) Could this have been some kind of brown algae? I thought that it would be soft.

Sorry, I could not get the pic to show up.

lynnejohn August 29th, 2012 21:04

Diesel Purge complete, no difference...

outthere August 30th, 2012 08:30

A new Tee fitting on the fuel filter is not a lot of $$ and easy to swap out yourself. if the Tee is bad or does not seat properly....

lynnejohn August 30th, 2012 19:06


Originally Posted by outthere (Post 3917566)
A new Tee fitting on the fuel filter is not a lot of $$ and easy to swap out yourself. if the Tee is bad or does not seat properly....

I got one a week ago and installed it tonight (seemed to fit more snugly into the fuel filter.) Let you know if it works in the morning. Anyone know what the ball bearing in the Tee is for?

All times are GMT -7. The time now is 00:58.

Powered by vBulletin® Version 3.8.5
Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.
Copyright - TDIClub Online LTD - 2017

Page generated in 0.07178 seconds with 8 queries
[Output: 16.84 Kb. compressed to 16.12 Kb. by saving 0.72 Kb. (4.26%)]