2002 jetta tdi stumble @ 2000rpm

DBW is in Boise.

If you call him he is VERY helpful over the phone - the main reason I went with him apart from his stuff bring top of the line.

I personally have a TD Tuning tune on my TDI, but I am a bit biased on them being a dealer.


Have you done any injector balance logs in VCDS at all - specifically when the issue happens? If you have any feel free to post them up or send them over.
 
Um......I just got VCDS. So, you'll have to explain how to do that. I saw an idle contribution page and it was every where. Negative, positive it was crazy.
 
Go into measuring blocks and look at group 13.

It may be what you did, "Idle speed smooth running control"


What are the numbers for each cylinder? Are they jumping around all over the place or fairly constant?



Back to your IQ adjustment, was it made on a completely warm engine with no load on it (AC off, fan off, lights off etc.?) I aim for around 4.2-4.5 typically, but this still shouldnt be the cause of your issue, just some fine tuning. You will also have to readjust this when you do the injector swap.

Your quantity adjuster could also be sticking causing issues. Lets start with simple and work from there.


When you had the MAF sensor unplugged did the car feel slower? You said no difference, but figured I should verify.
 
The car felt slower yes. Didn't rev as quick. The IQ was adjusted with a warm engine. The idle numbers didn't bounce but the variance between cylinders was large. I didn't write them down
 
Was it more than a difference of about 2 from lowest to highest value?


It should feel and rev slower without the MAF as well so thats normal.
 
I'm going off memory.....cylinder 3 was at 0.00, I want to say cyl 2 was at 0.5x, cylinder 1 was 0.7x? I think? I don't recall cyl 4. I do remember thinking, the large difference in numbers isn't good. But, I'm new to the alh game and thought it idled fine.....so, thise numbers might not be bad. Then I started researching more today and found the 2 difference.
 
I talked with DBW in Boise yesterday. He was very helpful over the phone. I told him my plans for the car. He suggested the DLC 1019 nozzle, I ordered them last night.

Ordered some supporting upgrades, hoping to get better mileage from it.
 
Malone tuning, 2.5 exhaust, egr delete. T stat and I'm gonna take the intake manifold off and clean it out
 
Make sure you get a new plastic housing with the T-stat, the like to crack over time and often break when removed.

Sounds like you are off to a good start mod wise, the next step would be a clutch and single mass flywheel.

I would recommend installing JUST the injectors first to see if that cures the issue.

Also use care when cleaning the intake and EGR housing to not drop any of the trash in the head. I personally prefer the burn method to clean the manifold and I scrape out the EGR while this is happening.
 
When you remove the intake it will make a bit more sense. The junk in the intake will be like tar, but the stuff on the head ports is dryer and can easily crumble.
 
The concern is that the valve shuts on it and doesn't fully close causing them to meet the pistons.

Not a highly likely thing but I just wanted to mention it.
 
Got it. I didn't think about that. Looking thru the intake/egr valve, the manifold doesn't look bad. But, it seems to be an issue with these cars.
 
It usually looks fine from that perspective, if you pull off the EGR housing it will show you whats going on in there.

I have also cleaned a few that people claimed to have taken to have shop cleaned before to find they did the scrape method very poorly leaving all kinds of crap still in there.
 
If you would rather have a cleaned manifold to just swap on so there is no down time I can help you with that. I think i have 2 intake manifolds that are cleaned just sitting on the shelf in my storage shed.

DBW are good people.
 
How much you want?

Pete was super easy to talk to and extremely helpful. He recommended a little bigger nozzle than I thought he would, but I'm ok with that. :p
 
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