ALH White Smoke at Startup and 2800 rpm 3rd Gear

2003 Jetta Wagon ALH, 5 Spd, 275,000 miles

Head Rebuilt around 225,000 miles (February of 2014)

Injectors Rebuilt with 520 Nozzles 225,000 miles (February of 2014)

Last weekend I finally got around to installing a Buzzken 2.5” downpipe to stock exhaust on this car. It had been leaking for a while at the flex joint and I believe the upcoming condition was present just less pronounced due to lack of concentration.

I am seeing heavy-ish white smoke (non-combusted fuel) at start up out of the tailpipe. There is also some stumbling at cold start. Today’s temp was 14F. Car started pretty fine but there is definitely at least a cylinder stumbling at start up. There are no CEL codes so I assume glow plugs are functioning sufficiently but have not pulled them to verify. Timing is at the high end of the green zone on VAGCOM. I checked the IQ yesterday and it was low at 1.8. I adjusted that so it was now getting 3.8 (leaner). This morning the symptom persisted. For about a month I have been getting an intermittent very slight hesitation and “hunting” at about 2800 rpm in 3rd gear. Now that the new downpipe is in place I can repeat that condition and usually, dependent on wind, can see a bit of white smoke out of the tailpipe at this rpm/gear. The car runs and drives great outside these issues.

Next step plan is to run a can of diesel purge directly through the pump. I did this years ago at maybe 100,000 miles. I am trying to eliminate the easy things before I move on to looking for an injector or pump issue. If that doesn't help I will also be doing a compression test although nothing looked out of place when the head was off 50,000 miles ago. I would appreciate some insight into how to most easily approach the diagnosis of he pump, injectors or anything else I may have missed. The pump is original and I have nearly exclusively run premium diesel in this car.

Update....This is occurring more in the +/- 2500 rpm range.

What's fuel mileage like (compared to when you didn't have issues)?

I would look at injector balance (via VCDS).

What's your timing set at? (at operational temp)

How did you change that IQ?

Mileage has been fair. Around town on generally short-ish trip tanks it's at 39-40. Road trips seeing highway speeds of 70+ see around 45. It's snow tire season too so I don't see that as being too bad.

Injection timing was checked with Vag-com a few weeks back and was near the top of the green zone. I adjusted the IQ with Vag-Com.

Heading home from the office tonight to check the injector balance, run some diesel purge through then check IQ, balance and timing again.

I will report back later....thanks.

Could be some oily stuff in the intercooler piping. Maybe get it real warm and run it hard for a few minutes.

So last night I rechecked everything. The timing was dead on at the green line on Vag-Com. IQ read 3.8 mg/str and injector balance was .31,-.19,.00,-.09 all at a coolant temp of 89.1C. That all seemed fine. I then ran a can of diesel purge directly through the pump by bypassing the vehicle tank. I ran the engine at various rpms up to 3,500 or so. I then went for a short ride and came home to recheck everything. The IQ was now 4.2 mg/str injector balance was .66,-.28, -.33, -.05. This was now at a coolant temp of 92.7C. I decided to recheck the timing while I was hooked up and it was now above the green line by 5 points. I retarded it to land between the middle blue line and the top green line. Outside ambient was around 55F.

This morning it was about 20F when I went out to start the car. I cycled the key twice then cranked it over. It started smoother and there was no stumbling or really any of the previous white smoke. I have not checked it for the 2500 rpm issue yet but will do so in the coming days.

My assessment at this point is that my timing was slightly advanced outside of specs but it was not showing up due to insufficient warming of the engine. This is odd though as VCDS won't let you test on an otherwise too cool engine and the chart compensates for temp. I suppose the Diesel Purge doesn't ever hurt either.

Things are still good at start up but yesterday I did notice the "smoke" out the tailpipe on the highway at about 2700 rpm. I don't know if it's oil, fuel or coolant at this point. I don't suspect coolant as I have not lost any over a long period of time. Maybe fuel because there is some hunting as I decelerate at that rpm but hardly noticeable. Oil is always a possibility it seems. Anyone have further thoughts?

Hoping to figure this one out....

More clues....

I noticed this week that sometimes when arriving home, placing the parking brake and getting out to open the garage door I hear the turbo whistle kick in, sustain for a bit then sometimes stop or continue. Should this be happening at idle ever? I changed the turbo actuator some years back and haven't had any issues since.

Any thoughts?

I don't think I ever heard any turbo whistle at idle.
Even working under the hood w/ the engine running.