Rough idle question, 2005 Passat TDI

lynnejohn

Veteran Member
Joined
Feb 7, 2002
Location
CT
TDI
2010 Jetta 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 ?

Thanks.
 

DezlDan

Veteran Member
Joined
Sep 21, 2005
Location
Richmond, B.C., Canada
TDI
2005 passat TDI Variant - United Grey
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

Veteran Member
Joined
Feb 7, 2002
Location
CT
TDI
2010 Jetta TDI
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.
 
Last edited:

sirpuddingfoot

Veteran Member
Joined
May 14, 2010
Location
Seattle, WA
TDI
05 Passat, 05 Jetta
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

Veteran Member
Joined
Feb 7, 2002
Location
CT
TDI
2010 Jetta TDI
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.

Thanks...
 

thundershorts

Top Post Dawg
Joined
Jul 15, 2010
Location
west chester pa
TDI
2015 passat tdi sel premium 2015 golf s tdi gls tdi b5.5, 2002 eurovan,Peugeot 505 td,Citroen cx25 prestige
I'll bet on the timing being a bit retarded.
 

lynnejohn

Veteran Member
Joined
Feb 7, 2002
Location
CT
TDI
2010 Jetta TDI
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

Veteran Member
Joined
Feb 7, 2002
Location
CT
TDI
2010 Jetta TDI
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?

Thanks
 

thundershorts

Top Post Dawg
Joined
Jul 15, 2010
Location
west chester pa
TDI
2015 passat tdi sel premium 2015 golf s tdi gls tdi b5.5, 2002 eurovan,Peugeot 505 td,Citroen cx25 prestige
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

Vendor
Joined
May 8, 2011
Location
NORTH BALTIMORE OHIO
TDI
2012 jetta premier DSG
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

Certified Volkswagen Nut & Vendor
Joined
Dec 11, 2001
Location
outside St Louis, MO
TDI
There are just too many to list....
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

Veteran Member
Joined
Feb 7, 2002
Location
CT
TDI
2010 Jetta TDI
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.
 

outthere

Veteran Member
Joined
Apr 28, 2004
TDI
2004 B5 Northern Green wagon
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

Veteran Member
Joined
Feb 7, 2002
Location
CT
TDI
2010 Jetta TDI
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?
 

lynnejohn

Veteran Member
Joined
Feb 7, 2002
Location
CT
TDI
2010 Jetta TDI
New Tee fitting and new hose clamps has not solved it. I'll keep plugging away.
 

thundershorts

Top Post Dawg
Joined
Jul 15, 2010
Location
west chester pa
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2015 passat tdi sel premium 2015 golf s tdi gls tdi b5.5, 2002 eurovan,Peugeot 505 td,Citroen cx25 prestige
you still haven't reported what the torsion value is set to. Its in all likelyhood still retarded. you don't seem to have vcds so maybe someone in your area does and can check the torsion value for you.
 

lynnejohn

Veteran Member
Joined
Feb 7, 2002
Location
CT
TDI
2010 Jetta TDI
you still haven't reported what the torsion value is set to. Its in all likelyhood still retarded. you don't seem to have vcds so maybe someone in your area does and can check the torsion value for you.
Ok, so if I can get the VCDS software I'll be able read the torsion value? I have an old MAC and can set up a Virtual Machine so I can run the software. Where would the Torsion vale be kept ? Thanks...
 

thundershorts

Top Post Dawg
Joined
Jul 15, 2010
Location
west chester pa
TDI
2015 passat tdi sel premium 2015 golf s tdi gls tdi b5.5, 2002 eurovan,Peugeot 505 td,Citroen cx25 prestige
you'll need the cable from ross-tech which contains the license. the vcds download is free' Just go to their site and most of your questions about it will be answered http://www.ross-tech.com/
 

lynnejohn

Veteran Member
Joined
Feb 7, 2002
Location
CT
TDI
2010 Jetta TDI
you'll need the cable from ross-tech which contains the license. the vcds download is free' Just go to their site and most of your questions about it will be answered http://www.ross-tech.com/
I've got the vcds and tried it out this morning but which section of the software package will I find where to see the value?
I did notice that after letting it idle for about a minute the idle suddenly went smooth (when I say suddenly I mean as if a switch was flipped.) I did not hear any relay clicking when it happened.
 

lynnejohn

Veteran Member
Joined
Feb 7, 2002
Location
CT
TDI
2010 Jetta TDI
Value was -0.5KW. What value is the EGR supposed to be when the car starts up cold?
When the idle suddenly went smooth, I thought I saw the EGR go up to 100% and stay there.
 

thundershorts

Top Post Dawg
Joined
Jul 15, 2010
Location
west chester pa
TDI
2015 passat tdi sel premium 2015 golf s tdi gls tdi b5.5, 2002 eurovan,Peugeot 505 td,Citroen cx25 prestige
actually the egr will sometimes show over 100%, like 100.6 or so. your torsion value is probably ok, but your egr valve may have been sticking and not opening, causing the rough cold idle. it may have suddenly opened when your idle suddenly smoothed out.
 

lynnejohn

Veteran Member
Joined
Feb 7, 2002
Location
CT
TDI
2010 Jetta TDI
actually the egr will sometimes show over 100%, like 100.6 or so. your torsion value is probably ok, but your egr valve may have been sticking and not opening, causing the rough cold idle. it may have suddenly opened when your idle suddenly smoothed out.
I logged the out put from startup till the idle smoothed and the EGR started at 100.6 briefly and then would swing between 65 to 80%. Then
at time 146 it went back to 100.6 and the idle smoothed out.

When it says 100.6%, is the valve open or closed at that point?

Thanks..
 

thundershorts

Top Post Dawg
Joined
Jul 15, 2010
Location
west chester pa
TDI
2015 passat tdi sel premium 2015 golf s tdi gls tdi b5.5, 2002 eurovan,Peugeot 505 td,Citroen cx25 prestige
the egr valve is all the way open normally at cold idle. ie: 100%. I suspect yours is sticking at least partially closed when its supposed to be all the way open at cold idle till eng temp reaches a set point. the cure may be cleaning the muck off it so it functions properly or replacing it possibly. look for threads as to cleaning instructions. its fairly simple to remove it. Hopefully others will add here if I've missed anything. As you may realize, your ross-tech purchace has already given you partial payback, as without it , this problem would still be eluding us.
 

lynnejohn

Veteran Member
Joined
Feb 7, 2002
Location
CT
TDI
2010 Jetta TDI
the egr valve is all the way open normally at cold idle. ie: 100%. I suspect yours is sticking at least partially closed when its supposed to be all the way open at cold idle till eng temp reaches a set point. the cure may be cleaning the muck off it so it functions properly or replacing it possibly. look for threads as to cleaning instructions. its fairly simple to remove it. Hopefully others will add here if I've missed anything. As you may realize, your ross-tech purchace has already given you partial payback, as without it , this problem would still be eluding us.
It was definitely worth the money as down the road I can quickly get some detailed engine info. I check the threads for cleaning the EGR and give an update.
 

lynnejohn

Veteran Member
Joined
Feb 7, 2002
Location
CT
TDI
2010 Jetta TDI
mine does the exact same thing and has a brand new OEM egr valve, nothing has changed.
Just when I thought I was getting close. If is not the EGR, then some sensor input that helps controls it.
 

Blackfatbob

Member
Joined
Sep 19, 2012
Location
SW Florida
TDI
2005 Passat GLS
Just when I thought I was getting close. If is not the EGR, then some sensor input that helps controls it.

Maybe some of the Veterans can chime in on this. I have read somewhere that the EGR sometimes goes through a calibration routine. My GLS will sometimes do this flakey stutter at idle, too. I attribute it to the egr being cycled for some unknown reason. With the VCDs you definitely have the right tool. Log your MAF actual vs required from idle to 60 mph or so can tell you alot. Boost pressure for the same thing although this is likely not a boost issue. There is also the shudder valve in the inlet to the intake manifold up stream from the EGR that may be doing something it shouldn't.
 

lynnejohn

Veteran Member
Joined
Feb 7, 2002
Location
CT
TDI
2010 Jetta TDI
Maybe some of the Veterans can chime in on this. I have read somewhere that the EGR sometimes goes through a calibration routine. My GLS will sometimes do this flakey stutter at idle, too. I attribute it to the egr being cycled for some unknown reason. With the VCDs you definitely have the right tool. Log your MAF actual vs required from idle to 60 mph or so can tell you alot. Boost pressure for the same thing although this is likely not a boost issue. There is also the shudder valve in the inlet to the intake manifold up stream from the EGR that may be doing something it shouldn't.
Ok,
Tomorrow I'll run the following data:

EGR %
MAF Actual
MAF Required
Boost Pressure

Is there any other data that would effect the EGR % as after a minute or so, the EGR goes to 100% and the idle smooths out.
 
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