Need some input! Cloud of grey smoke on startup

[wonneber]

Good point on reduced airflow being a possible source. I've checked the IC piping and there are no leaks, and monitoring boost seem normal to me.

You could take the intake hose off at the ASV and start the car. (cold)
If the smoke is the same look inside the ASV for a clog.
If less maybe oil in the IC restricting air?

 

[jmodge]

Your idea of checking for a leaking injector is a good one, I wouldn’t be concerned with the bore. Leak down test for valves. Look for increased consumption of any fluids

 

[jmodge]

Ok, you did monitor boost, I missed that

 

[wonneber]

The smoke is at startup.
How much boost is there?
Not much.
I'm thinking rule out air restriction.

 

[jmodge]

Post #1 says low rpm issues. Doesn't the n75 apply vacuum at startup closing the vanes? If so, that would supply boost, boost is decreased as rpms climb and is no longer needed. I hear my turbo at idle. No boost would be an air restriction.
Grey smoke sounds like fuel burning to me, not oil. So, I am thinking boost or fuel leaking into the cylinder while sitting. But the problem persists until the engine is warm, apparently. So, I don't think fuel sitting in the cylinder would last that long, nor would a small amount of oil. I believe somewhere he stated he check for oil coming from the turbo and found none.
That's why I would start at eliminating any possible cause of boost issues.

At any rate, I can't see or smell it, so I am just guessing like everyone else. So, I am going to PM you Matt's number.

 

[jmodge]

You could take the intake hose off at the ASV and start the car. (cold)
If the smoke is the same look inside the ASV for a clog.
If less maybe oil in the IC restricting air?

And that is something that costs nothing to check

 

[J.P.]

You could take the intake hose off at the ASV and start the car. (cold)
If the smoke is the same look inside the ASV for a clog.
If less maybe oil in the IC restricting air?

I pulled the intake hose off and inspected the ASV and there was minimal buildup, but I did not start the car with that hose off. I'll check it.

Grey smoke sounds like fuel burning to me, not oil. So, I am thinking boost or fuel leaking into the cylinder while sitting. But the problem persists until the engine is warm, apparently. So, I don't think fuel sitting in the cylinder would last that long, nor would a small amount of oil. I believe somewhere he stated he check for oil coming from the turbo and found none.
That's why I would start at eliminating any possible cause of boost issues.
At any rate, I can't see or smell it, so I am just guessing like everyone else. So, I am going to PM you Matt's number.

Thanks for your line of thought with this. I will revisit, and compare boost logs for this car and the good running ALH while I wait for injector washers.

Matt Whitbread has worked on our other cars and has done great work (and is w/in 2 hrs). I am working to solve this one as it is not currently a critical daily driver.

My diagnostic ability at this stage has moved from "I don't know what I don't know" to "I know what I don't know". I'm getting better, but I'm not to "I know what I know" yet!!

 

[rrgrassi]

Send an oil sample off for testing. It will tell you if fuel is getting onto the oil. Fuel on a dripping on a piston can work its way into the crankcase.

 

[wonneber]

I pulled the intake hose off and inspected the ASV and there was minimal buildup, but I did not start the car with that hose off. I'll check it.

My diagnostic ability at this stage has moved from "I don't know what I don't know" to "I know what I don't know". I'm getting better, but I'm not to "I know what I know" yet!!

I'm pretty sure I had mine started with the intake hose off.
Was several years ago.

As time goes on you will learn more & more from reading here.
Many smart people here.

The last part about knowledge is the best thing to know.
The owner of the repair shop I help in occasionally told me about it years ago.

 

[WildChild80]

I pulled the intake hose off and inspected the ASV and there was minimal buildup, but I did not start the car with that hose off. I'll check it.


Thanks for your line of thought with this. I will revisit, and compare boost logs for this car and the good running ALH while I wait for injector washers.

Matt Whitbread has worked on our other cars and has done great work (and is w/in 2 hrs). I am working to solve this one as it is not currently a critical daily driver.

My diagnostic ability at this stage has moved from "I don't know what I don't know" to "I know what I don't know". I'm getting better, but I'm not to "I know what I know" yet!!

I bought my first TDI knowing how to work on cars... assuming these cars were like every other car. Didn't really understand much about diesels... Steep learning curve, this forum, YouTube and trial and error have taught me volumes. The hardest part is finding good parts at a good price with great shipping...so far idparts has done me very good.



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[J.P.]

An update:

Pulled the intake hose off the ASV and started the car - still smoke.
Intake looked very clean with just a light coating of soot (confirming PO's statement of cleaning the intake). Unless there is some obstruction anomoly at the bottom of the intake I can rule out air restriction.

Had my son operate the accelerator pedal while I watched the fuel line. No air bubbles at all at idle, then BIG air bubbles every second or so at 1200 rpm, the bubbles seemed to reduce as speed increased beyond that. I went ahead and replaced all the fuel lines in the engine compartment. I'll test in the morning.

Logged boost and it looked normal. Logged MAF requested and actual and found something odd. At idle requested MAF is about 1/2 of actual. At 1200 RPM MAF actual DROPPED. Is this normal EGR control? (other car has EGR delete).


Engine Air Mass Air Mass EGR
Speed Specd Actual Solenoid
/min mg/str mg/str %
903 270 490 4.8
1176 280 235 80.1
1323 280 275 52.2

 

[jmodge]

Have you ever unplugged the MAF to see if anything changes? I had that troublemaker deleted on mine, so I never bothered to learn the details of logging it.

 

[eddieleephd]

Jmodge asked the right question here.
If the boost is following requested then the MAF as well would with a clean intake.
Unplug the MAF and see if it remains, runs default settings when unplugged. Otherwise, swap it for a known good one

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[jmodge]

You are in the fortunate position of having time and another good running car to swap parts between without costing you money. Do both cars run the same MAP? Also have someone start it and watch the vnt lever on startup. I believe it should hit the stop providing full boost, at least momentarily, search and confirm that.

 

[jmodge]

JETaah and or Andy Bees are a couple guys you could pm and get clear acurate info from

 

[wonneber]

Logged boost and it looked normal. Logged MAF requested and actual and found something odd. At idle requested MAF is about 1/2 of actual. At 1200 RPM MAF actual DROPPED. Is this normal EGR control? (other car has EGR delete).

If you decide to replace the MAF get an OEM unit.
Aftermarket electronics have been known to raise havoc with German cars.

 

[WildChild80]

If you decide to replace the MAF get an OEM unit.

Aftermarket electronics have been known to raise havoc with German cars.

Spend the money on a Bosch... totally agree...

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[WildChild80]

You are in the fortunate position of having time and another good running car to swap parts between without costing you money. Do both cars run the same MAP? Also have someone start it and watch the vnt lever on startup. I believe it should hit the stop providing full boost, at least momentarily, search and confirm that.

I thought we had come to the conclusion that when you start it up it goes to the stop for zero boost and reduction of vacuum caused boost for better response

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[Nero Morg]

Have you tried doing a diesel purge treatment? I'm still sure it's worn nozzles, but diesel purge might help clean it up a little. Not completely fix, but an improvement.

 

[wonneber]

I thought we had come to the conclusion that when you start it up it goes to the stop for zero boost and reduction of vacuum caused boost for better response

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That's what I thought.
My vacuum to the actuator drops down when I take off, boost gauge go up.

 

[eddieleephd]

That's what I thought.

My vacuum to the actuator drops down when I take off, boost gauge go up.

The vacuum must have a release line and if the one way valve is on the wrong line it'll prevent boost.


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[jmodge]

Actuator at rest holds the vanes open, vacuum closes them increasing heat, producing boost. As heat builds the vanes open to release pressure and control overboost. Loss of all vacuum would result in “failsafe mode” to prevent the turbo from self destruction

 

[jmodge]

J.P., Never noticed anything mentioned about unhooking the actuator and checking vane movement. Have you run it up hills getting on it from low rpm to heat up the turbo? If they just recently got stuck, it may clean them out. Have you checked the actuator lever to see if it hits the stop to provide full boost?
Curious about that air you saw too.

 

[jmodge]

If your not producing enough boost relative to rpm your MAP would read that and I believe the ecu would increase fuel to increase rpm, but not getting proper air it would smoke and stumble.

 

[J.P.]

Update:
I swapped MAFs between cars. Installed in this car MAF requested and MAF actual are very close all the time. If I accelerate hard MAF actual will get up to 800.
Here's what I saw though. Starting the car with MAF plugged in produces a giant cloud of smoke, and some stumbling at idle, significant smoke if I put rpms to 1200 or so. Unplugging the MAF while running immediately reduces the smoke (not all gone but much less), plugging back in brings it back.

When I look at logs, unplugging the MAF forces EGR solenoid N18 % to go to 4.8% (same value as wide open throttle). If I understand correctly this means that EGR is bypassed (no EGR). So before the engine is fully up to temp I am getting more smoke with EGR, a lot less with no EGR.

When the engine is warmed up (seems like coolant temps are above 80deg C), I'm not getting smoke even with EGR solenoid % above 50% at idle and low rpms. Power seems good for a bone stock car (I'm used to a tuned ALH), turbo is functioning. I ran boost logs, but they didn't save, so I've been unable to look at them closely.


Can the EGR accumulate oil in any way? My smoke is grey so I ruled out coolant, but maybe this is back in play? (too few miles since symptoms started to determine coolant loss).

 

[eddieleephd]

Yes the EGR can accumulate oil. I would say it's rare for it to accumulate much oil. However, it's at the bottom of the intake tube and gravity will cause some to migrate in.
Reality is that if it gets to temperature and runs for a decent amount of time it should burn out. There would have to be an excessive amount traveling through the intake to accumulate much at all.


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[eddieleephd]

Did you swap injectors?
Looking back at everything the number 3 could be leaking into the cylinder causing the smoke. With those miles I would consider reconditioning the head next timing belt. There's the issue with valve seals and guides wearing with that high of milage.

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[jmodge]

You can run just your ecu over to Whitbread and have it tuned. TDtuning, he has a benchtop harness to do it from. Delete the MAF, EGR, and Immobilizer if you do. MAF delete made little to no difference to economy in mine. I also deleted ASV.
You can swap ecu's if your other car has immo delete to see what happens. EGR function changes fueling. Unplugging maf probably affects egr, it goes to a default mapping. I never studied it much, just deleted the crap since we don't need it here. I think you may be moving in the right direction.

 

[jmodge]

You could have a wire worn through somewhere also, all that crap is tied together in the harness. Just because your injectors show lack of balance doesn't necessarily mean injectors are off. Especially if it is number 3. Put your injectors in the good car and see what they do.

 

[jmodge]

Out of curiosity, what is your injector balance with the maf unplugged?