Can't pass California Snap Test for Smog

kev2t72@gmail.com

New member
Joined
Feb 19, 2013
Location
California
TDI
2004 Passat TDI
Should a 2004 Passat TDI put out any smoke when throttle is pressed from idle to 2500 RPM? Mine puts out a small puff, but once RPM's get up, the smoke is no longer there. Smoke is black, so probably un-burned fuel. I did remove both mufflers for the sound, and VW service told me they found nothing wrong with the car except missing mufflers, and wanted me to put those back on for $1500. Could I have a oil filled intercooler slowing airflow, or a blocked EGR valve? Neither of them have ever been looked at. I have one month to fix issue. Thanks,
 

narongc73

Veteran Member
Joined
Nov 14, 2005
Location
VA/OH
TDI
2006 Jetta TDI
california'ed. I hear shops jump up and down when they hear of emission failures in CA. Cha ching.
 

hey_allen

Veteran Member
Joined
Nov 25, 2006
Location
Altus, OK
TDI
2000 Jetta TDI
As far as exhaust goes, barring fixing everything else, couldn't you get a system from another car of the same model in the wrecking yard for a lot less money, and bolt that in for testing purposes?

I don't know BEW engine management or typical behavior, so I can't even venture a guess as to normal operation.
 

VeeDubTDI

Wanderluster, Traveler, TDIClub Enthusiast
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Jul 2, 2000
Location
Springfield, VA
TDI
‘18 Tesla Model 3D+, ‘14 Cadillac ELR, ‘13 Fiat 500e
The smoke is not the result of the missing mufflers. You can pay VW $1,500 but it will still fail the snap test.

You might have some good results from biodiesel and/or cetane boost additive like PowerService silver bottle.

If all else fails and everything engine and fuel delivery related is in good working order, you might want to consider talking to a tuner about cleaning the car up a bit so that it will pass emissions.
 

caideN

Well-known member
Joined
Dec 31, 2017
Location
CA
TDI
02 Jetta Wagon TDI
I thought CA just plug in the OBDII and run a diagnostic that way. Since getting rid of the pipe sniff test, I've never seen a tech "Snap test."
 

Franko6

Vendor , w/Business number
Joined
May 7, 2005
Location
Sw Missouri
TDI
Jetta, 99, Silver`
There are three reasons that you would have a puff of black smoke when you hit the throttle.

1) The EGR is sticking open a bit. The throttle will lag, then suddenly, BOOM! you have a power surge, which can smoke. Clean the EGR valve. Less likely...

2) You have a Turbo Actuator rod that is closing too much. When you hit the throttle, the actuator wants to open the VNT on your turbo, but the the vanes that are closed too much, and the exhaust pressure keeps the vanes closed...It smokes and belches. Let the pedal off, then back on, it passes the crisis and the vanes open correctly. There is a goofy wire lasso we make to correct that problem. Somewhat likely...

3) Your cam is worn out. Remove the valve cover and look for the tell-tale signs of galling on the base circle of the cam. If you see this adverse wear, and also, the tops of the lobes have sharp edges, especially on the exhaust lobes (1, 3, 6 and 8), you have a worn cam. Because of the reduced lift of the cam, not enough boost pressure comes in with the associated fuel charge. This causes the first few seconds of engine revving to puff black smoke. Very likely....

In CA, they want to eliminate diesels. We do have a cam kit, if you like. The other 'fixes' are just a matter of know-how.

Let us know if we can be any additional help.
 

KLXD

Top Post Dawg
Joined
Aug 22, 2009
Location
Lompoc, CA
TDI
'98, '2 Jettas
I thought CA just plug in the OBDII and run a diagnostic that way. Since getting rid of the pipe sniff test, I've never seen a tech "Snap test."
Never was a sniff test on Diesels. Last time I went there was no snap test.
 

oilhammer

Certified Volkswagen Nut & Vendor
Joined
Dec 11, 2001
Location
outside St Louis, MO
TDI
There are just too many to list....
Cannot speak to the CA test procedure, but my own BHW has always had a more smoky exhaust at takeoff than other TDIs, and it seems pretty typical for them. They have a HUGE charge air tract, so there is a point where the ECU can put fuel in, but the turbo has not had a chance to get the air the ~8 feet back around to the intake.

What I find is running the car hard (doing some hard floorboarded runs, up to redline) once the car is warmed up, will help blow out any crud and help get the car cleaned up.

You may also remove the EGR valve and make sure it is clean. The EGR is on at idle (unless it idles for a few minutes), so if it is a bit gunked up, the air flow will be less than ideal right off idle.

The BEWs and BRMs don't seem to ever exhibit this quick tip in puff like the BHWs do.
 

Mike_04GolfTDI

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Joined
Nov 19, 2003
Location
Richmond, BC, Canada
TDI
Mine: 2019 Golf R DSG, Wife's: 2015 Golf Comfortline TDI
Another possibility could be worn or dirty injectors.

If the spray pattern is not good, maybe you'd get a bit of smoke.

A cleaning with Lubro Moly Diesel Purge might help if the injectors just need cleaning. It needs to be run directly from the can, full strength.

If they're worn, that's a more costly problem requiring an expert to overhaul the injectors.
 
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BobnOH

not-a-mechanic
Joined
May 29, 2004
Location
central Ohio
TDI
New Beetle 2003 manual
Did the inspector tell you what the specific failure was? Did he say smoke?
I would try OHs workaround -
What I find is running the car hard (doing some hard floorboarded runs, up to redline) once the car is warmed up, will help blow out any crud and help get the car cleaned up.

 

TDIMeister

Phd of TDIClub Enthusiast, Moderator at Large
Joined
May 1, 1999
Location
Canada
TDI
TDI
Kind of ironic that smoke is actually not a major contributor of "smog" per se, but a specific ratio of HCs (VOCs) and NOx.

Nevertheless, all the usual suspects in terms of maintenance and mechanical condition have been thoroughly covered. Once these are addressed, I suggest to run a tank or two of high % Biodiesel or Propel, and I also second and third the suggestion to give it a real good ol' Italian tune up driving all the way to the inspection station. :D
 

n1das

TDIClub Enthusiast, Veteran Member
Joined
Jun 11, 2002
Location
Nashua, NH, USA
TDI
2014 BMW 535xd ///M-Sport, 2012 BMW X5 Xdrive35d, former 3x TDI owner
Cannot speak to the CA test procedure, but my own BHW has always had a more smoky exhaust at takeoff than other TDIs, and it seems pretty typical for them. They have a HUGE charge air tract, so there is a point where the ECU can put fuel in, but the turbo has not had a chance to get the air the ~8 feet back around to the intake.
What I find is running the car hard (doing some hard floorboarded runs, up to redline) once the car is warmed up, will help blow out any crud and help get the car cleaned up.
You may also remove the EGR valve and make sure it is clean. The EGR is on at idle (unless it idles for a few minutes), so if it is a bit gunked up, the air flow will be less than ideal right off idle.
The BEWs and BRMs don't seem to ever exhibit this quick tip in puff like the BHWs do.
What oilhammer said. "Drive it like you stole it" applies.

I have never heard of CA doing a snap test for diesel cars. The tech noticed the smoke and the amount for your car might actually be normal. The tech probably works on gassers most of the time. That doesn't imply there actually is snap test that it has to pass.

If the car has to pass a snap test in CA, I have an idea for an electrical mod that might help. In the CR TDIs and in my BMW diesels, you absolutely cannot snap accelerate them to full throttle no matter how fast you slam the fuel quantity request pedal to the floor (can't call it a "gas" pedal :)). The rate of throttle change as seen by the ECU is carefully controlled during by design to prevent making smoke. The ECU does a quick but carefully controlled ramp up to full throttle during a snap event instead of doing it as a step function. The PDs and older TDIs can be snap accelerated but CR TDIs cannot be. The idea I had for a mod on PDs and older TDIs is to add capacitance to the go-pedal circuit to slow down the throttle input to the ECU to prevent making smoke during a snap test. It will roll into full throttle instead snapping to full throttle when you stomp on the pedal. It's all about controlling the rise time of the throttle input to the ECU.

I've never actually tried this as an electrical mod but I was thinking about it given that our cars use a drive by wire throttle system.

:)
 
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dlai

Top Post Dawg
Joined
Jun 6, 2002
Location
The Insane Asylum Known As CA
TDI
2005 Passat, Stonehenge Gray, 2002 Black Golf 5M
There is no snap test. I just had my smog done last week on my BHW with no issues. Do you have any Propel synthetic diesel stations near you? You can try to run two tanks of that first and then do the smog test again. I do that with my Golf since it's highly modded and it reduces the black smoke quite a bit.
 

KLXD

Top Post Dawg
Joined
Aug 22, 2009
Location
Lompoc, CA
TDI
'98, '2 Jettas
I didn't think so. Maybe the tester was doing his own thing. If so the OP needs to be raising ell, getting a refund and complaining to the ARB.

My AHU should be coming up again in a few months so I guess I'll find out. My Dodge too if I decide to start driving it again.
 
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torman

Veteran Member
Joined
Jan 17, 2007
Location
NorCal and Upstate NY
TDI
Mk4 Golf and Treg
Take it to another inspection station. Most just check for no check engine lights.

If you mean CAT was removed (and not actual mufflers), that is a whole other issues, as many inspection stations look for CAT as a proxy for seeing if any emissions items have been removed. A lot of diesel trucks went straight pipe years back (before CA ramped up inspections on them) and shops have been instructed to inspect exhaust system for mods.
 

Mike_04GolfTDI

Top Post Dawg
Joined
Nov 19, 2003
Location
Richmond, BC, Canada
TDI
Mine: 2019 Golf R DSG, Wife's: 2015 Golf Comfortline TDI
We used to have emissions testing here in British Columbia. Because of the way the system works, I didn't have to take my car in until it was six years old.

Well, upon my first visit to the inspection station, I noticed that my vehicle registration documents had the fuel type listed as "Gasoline!"

I pointed this out to the inspector, and he was able to change the fuel type to diesel in the vehicle registration system.

Had I not brought it to their attention, I guess they would have been testing my vehicle using whatever procedure they use for a gasoline engine car. Maybe it would have failed?

Do your registration documents in California mention anything about fuel type? Make sure it's correct!
 

narongc73

Veteran Member
Joined
Nov 14, 2005
Location
VA/OH
TDI
2006 Jetta TDI
As a few said before use biodiesel. I put a bottle of crisco in the UK and it worked. I had failed the day before.
 

flee

Veteran Member
Joined
Sep 19, 2011
Location
Chatsworth, CA
TDI
2002 Jetta GLS wagon
As a few said before use biodiesel. I put a bottle of crisco in the UK and it worked. I had failed the day before.
Where exactly is the TDI's UK located?
Please don't do this. A tank or two of biodiesel can't hurt, though.
 

KLXD

Top Post Dawg
Joined
Aug 22, 2009
Location
Lompoc, CA
TDI
'98, '2 Jettas
The point is the OP, who's disappeared, got ripped off based on dlai's recent experience.

If he just goes to another tester he's out money. Also, the original clown may have put some notes in the system about it failing which could cause him problems.

Missing mufflers are probably grounds for a fail but that's not what got him.
 
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