Passat Occasional "Miss" at cold idle

[Bohonk]

New to TDI's but not new to mechanics..

So I have had this 05 Passat for a little bit now and its time to start digging into it.

It does have stage 2 tune from Malone, Egr delete, Maf delete, immo delete...

I am having an issue with its idle on cold starts. When I first start it up after its been sitting, it will idle ok, then start randomly "missing". Few times it will miss consistently for a few seconds then idle ok, then miss, then idle, etc... Its totally random, and only happens when cold. If its missing and you press the pedal, it goes away. Once its been idling for aa few minutes or you go drive it, it doesn't miss again until next cold start. The other note is that there is a fair amount of white smoke when cold. I know there is some oil in the system from a turbo going out but maybe its related..

Anyway.. I don't have VCDS, but I do have an autel that does quite a bit. Doing some reading leads me to believe its an injector issue so I have the injector quantity info
It is usually something like this when its missing (Forgot to grab exact numbers but this is close.

013-1 injection quantity cylinder one -1.49
013-2 injection quantity cylinder two 0.45
013-3 injection quantity cylinder three -2.99
013-4 injection quantity cylinder four -0.50

After a short time and it stops missing (2 minutes at 2 grand this time) the numbers went down to this

013-1 injection quantity cylinder one 0.33
013-2 injection quantity cylinder two -0.64
013-3 injection quantity cylinder three -0.21
013-4 injection quantity cylinder four 0.49


It runs great on the street and idles great when warm. This is only with a cold start and seems to be regardless of the outside temperature. Did it in the middle of summer, and now it's 30's and it does it the same.

Any directions would be great and I can get more info if needed while I have the scanner with me. I am just lost with all of the information and these diesels are new territory for me.

Thanks!

 

[efeballi]

White smoke may be an indication of unburnt fuel. As you have noted, injector 3 looks to be acting up, an overfueling injector may explain both the rough idle and the white smoke. There is a procedure for visual inspection of the camshaft that drives the injectors. I'm not sure why the rough idle problem pops up only when the engine is cold though. My gut feeling is that this will boil down to either a bad camshaft or a bad injector.

Also a good idea to check the camshaft torsion value, if you can do it with the diagnostic tool you have.

edit: you could swap injectors between cylinders to know for sure if the problem is with the injector or something else like compression or camshaft lobes for that cylinder, but AFAIK the #3 injector is different from others so you can't move it to another cylinder.

 

[Bohonk]

Awesome yeah, I plan to pull the valve cover. Any idea what block the torsion valve is under? And what the value should be? I will check in a little bit and report back my findings.

*** I was lazy. I found the info I needed.***

 

[Bohonk]

White smoke may be an indication of unburnt fuel. As you have noted, injector 3 looks to be acting up, an overfueling injector may explain both the rough idle and the white smoke. There is a procedure for visual inspection of the camshaft that drives the injectors. I'm not sure why the rough idle problem pops up only when the engine is cold though. My gut feeling is that this will boil down to either a bad camshaft or a bad injector.

Also a good idea to check the camshaft torsion value, if you can do it with the diagnostic tool you have.

edit: you could swap injectors between cylinders to know for sure if the problem is with the injector or something else like compression or camshaft lobes for that cylinder, but AFAIK the #3 injector is different from others so you can't move it to another cylinder.

Interesting the #3 injector would be different from the rest. I checked the torsion value and it was at 1.4. I did a little finicking with it as well as taking the valve cover off. I got it to -0.5, which is far as my research shows is a decent starting point if not ideal.

With the valve cover off I was able to inspect all of the cam lobes. One detail that I left out because I didn't want to jump to conclusions is that 15,000 miles ago, this engine was replaced with another used one. I figured at that time they would've been smart enough to replace or at least inspect the cam for damage. However, since these injectors are expensive, I figured they would've reused injectors from the old engine in this engine. After inspecting everything the cam lobes all looked great. I also checked the injector connections and tightened them up a little bit because I know they are known to loosen up.

The lucky thing is that I have another 05 Passat that I am keeping the engine for an engine swap. I know this engine was running perfectly and everything is in good shape. I can easily swap the injectors, I just haven't had the time and I wanted to make sure the injector was the culprit. I know these injectors are a little tedious to replace, but I have done much harder jobs on gassers so I feel like I should have the ability to do this haha.

Tomorrow morning I will check the injector quality numbers again since it will be cold. I took it for a spin tonight and it's running great.

 

[Bohonk]

Same issue again this morning when cold.. still number 3 injector going to 2.99.

 

[efeballi]

At this point it looks to me like the #3 injector is the culprit. The #3 is different as it measures the start, duration and end of ignition events. If you have compatible injectors in your other car, you should definitely try swapping over at least the #3 injector. Or better; if that other engine runs fine, run the injection quantity measurement there and if injectors look to be more closely aligned, swap over all injectors.
I've read that it is better if injectors are swapped together and not one by one, but I don't know for sure, you should research this yourself and make a decision.

 

[Bohonk]

I am hoping that’s it considering I have a “spare”. I can’t see how the other engine is running because it’s on a stand. The car was parted out a few months ago, but I drove it around for 6 months without issues. I will do some research and post back once I’ve swapped some things around

 

[Bohonk]

Well that was quick. Swapped injector 3 and the smoke and misfire went away. Runs like a champ now.

Numbers were:
-0.68
0.14
-0.09
0.54

Glad I got it figured out. Sold it 2 days later! But happy because it will help me with my future problems of my BHW swapped jeep.

 

[efeballi]

good to know, and good luck with the TDI jeep!