High NOx - failed emissions test

[fodegaar]

Hi All,
bought a 1993 Eurovan Weekender (auto) down in the States and trying to import it to Canada. It just failed the Ontario emissions test on too high NOx values. The limit is 661 and the recorded value was almost twice that at 1216. The other values on CO% and HCppm were fine.

Any suggestions to what might cause this? Has anybody had same experience?

Many thanks,
Fredrik

[r39o]

New cat.

PLUS PLUS PLUS make sure all the electrical connections are clean and ALL the vacuum lines are fresh.

BTDT
_________________
"Use the SEARCH, Luke" But first visit the Vanagon FAQ!

1990 Multivan EJ 22, Rancho trans 0.82 4th, Small Car front AC, CLKs w/ 215/65-16, homemade big brakes 303mm, Konis, Recaros, etc....

Click to see my ads for Cup holders, Subaru clutch fix and CLK wheels (no wheels currently)

[vwlovr]

[Howesight]

NOx is very sensitive to good Oxygen sensor function, so check that too. Also, if that year vehicle has an EGR system, check whether it is functioning properly. Poor EGR function can overwhelm the catalytic converter's ability to clean up NOx since EGR has a strong inpact on reducing NOx levels before they get to the catalyst. The vacuum hoses that activate the EGR valve on most systems can develop leaks since they are exposed to so much exhaust manifold heat. So, replace those hoses (very cheap to do) as part of dealing with this testing fail.

Good Luck!!

PS: Let us all know what the problem was when it's solved.
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'86 Syncro Westy SVX

[fodegaar]

Hi ,
and thanks for all the responses. I ended up taking it to the local VW dealer service-shop who suggested replacing the cat. On their recommendation they replaced it with an OEM part which cost over $1200 *ouch*. Long story short, it then passed emissions with a NOx value of 2 (!!?!). The other readings also went significanctly down, so at least I am driving a greener van

Best,
Fredrik

[r39o]

Can you say "Bend me over?"

Or what is the equivalent in Canadian, eh?

Is that EV even worth that much green to be green?

Dang....
_________________
"Use the SEARCH, Luke" But first visit the Vanagon FAQ!

1990 Multivan EJ 22, Rancho trans 0.82 4th, Small Car front AC, CLKs w/ 215/65-16, homemade big brakes 303mm, Konis, Recaros, etc....

Click to see my ads for Cup holders, Subaru clutch fix and CLK wheels (no wheels currently)

[oldhead]

I know this is an old thread I'm hoping someone is looking, I just failed the emissions test again on my 91 Vanagon GL, 2.1L Automatic. I'm the original owner, 183,000 miles, have NEVER had an issue with the emissions test, yes I know, hard to believe. Everything on the engine is original except for the starter, water pump, and the exhaust system which has been replaced as various parts failed, the vehicle is 100% bone stock. I failed the test previously after a tune up-new plugs and plug wires, new fuel filter, oil change with oil filter, new air filter, new distributor cap with rotor, had high NO readings, all else fine, mechanic suggested the cat might be the problem. I pulled the cat and sure enough the honeycomb was fried, I replaced it and the O2 sensor for good measure. I just crushed emissions except NO at 15 mph, I live in No. VA just across the Potomac from DC so the van gets tested on the dynamometer every two years. The readings are as follows: @15 mph, HC ppm: limit 144, reading 8. CO%: limit 1.117, reading 0.03. NO ppm: limit 965, reading 1132. RPM: 1079 valid and Dilution % 17.23 valid. @ 25 mph, HC ppm: limit 140, reading 7. CO% limit 1.45, reading 0.02. NO ppm: limit 879, reading 799. RPM 1163 valid and Dilution % 17.12 valid. So the NO did not pass at 15 mph and did pass at 25 mph. Any suggestions?

[oldhead]

Forgot to add something, the van runs GREAT, however it will not idle correctly until it is warmed up, I have to keep my foot on the gas and hold it around 1200 RPM until the engine is fully warmed, this is whether it is 90 degrees or 20 degrees outside. Also, even when fully warmed if I leave the trans in drive at a stoplight it will stall, if I put it in neutral it idles fine.

[fraggle00]

How is your fuel tank? You may have some vacuum leaks that are throwing things off. The emissions results are representative of your problems during warm up and idle.

There may be a temp sensor failing as well. We might be able to r it through some testing if you're near manassas.
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'91 Vanagon Carat
'87 Porsche 928S4 DOWN
'12 Fiat 500 Abarth

[Howesight]

Hey Oldhead:

I feel your pain since we used to have emissions testing here in BC right up to 2014. You have replaced all the right parts and done all the right things. There is only one further part replacement/repair that might solve your emissions fail. Remove your injectors and have them cleaned and flow tested. Remember that the WBX EFI system is "batch fired" and does not distinguish cylinders that are running lean or running rich. The oxygen sensor receives an exhaust flow that combines rich running cylinders with lean running cylinders. More modern cars' EFI systems can detect individual cylinder mixture, but not the WBX system. When new, the WBX injectors all flow identical amounts and have identical spray patterns. As they age and accumulate deposits, the uniform flow and spray patterns degrade, but not equally.

If the injectors are not all injecting at the same flow rate and same degree of atomization, then there will be uneven actual and effective air/fuel ratios (AFR). By "effective" AFR, I am pointing out the difference between a dirty injector that squirts a stream of fuel rather than a highly-atomized mist, as it was designed to do. Such injectors reduce the ability of the fuel to burn completely and allow a significant part of the fuel to accumulate on the cylinder wall and be scraped into the crankcase by the oil rings, instead of being burnt. That cylinder produces excess NOx, in excess of what the cat can reduce.

Another trick you could use ( but really only a trick, since it reduces fuel efficiency) is to install an extra-cold thermostat. Lowering the in-cylinder temperature reduces the amount of NOx produced.

The finaltrick would be to add water-injection to your van. That will definitely cure the NOx problem, but is not simple nor cheap.
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'86 Syncro Westy SVX

[oldhead]

Thanks guys, I'll check the fuel tank and connections (still original) and I'll take a look at the injectors (still original, never been apart). Gotta keep the old girl running all four of our kids rode in car seats in her and they all learned to drive on her.

[fraggle00]

Mine was right on the limit with an Evap setup that had turned to goo, And a brand new cat. I couldn't even fill the tank without sloshing some out. If your seals are original, that would be my bet. It isn't a hard job, a good day ahold be enough. Get at least one spare rollover valve, you will probably break one taking things apart.
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'91 Vanagon Carat
'87 Porsche 928S4 DOWN
'12 Fiat 500 Abarth

[84GL]

I had the same problem with my vanagon. It failed on the NO at 15 mph by 25 points and passed at 25 mph by 50 points. I read some threads on this website and then found a Cat Converter made by Magnaflow from the BusDepot web site that needed to be welded on. It was $110 and I went to the local muffler shop and that cost me $85 for installation.
I looked for the link but could not find that one anymore. But this link may help the next unsuspecting victim. I you buy the California model you cant go wrong since we have very strict allowances.

http://www.magnaflow.com/02converters.asp

Click on Truck/SUV on the dropdown in the upperleft to get started.

[oldhead]

I finally jacked the old girl up (that just sounds wrong) and much to my surprise the fuel tank is in excellent shape, zero rust! In fact zero rust underneath, amazing since this vehicle has never been garage parked. I'll replace all seals on the tank, the fuel tank (crossover) vent tube, the fuel lines I cut and go ahead and put a new fuel sender unit in since everything will already be out, the fuel gauge has been acting screwy lately. Think I'll also replace the coolant temp. sensor too since it's taking as long for the van to warm up whether it's 90 degrees or 15 degrees. If she doesn't pass again then I'll look at the fuel injectors. Thanks for ALL the feedback.