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Failed E-TEST => High NOx ~ Any Solutions?

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  • Aug 2nd, 2010 4:53 pm
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Sr. Member
Apr 29, 2010
665 posts
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London

Failed E-TEST => High NOx ~ Any Solutions?

I own a 1991 Mercedes 190E 2.3. The vehicle has just FAILED the E-Test here in Ontario. According to the report it passed every metric but failed only on the "NO ppm" (limit: 700, reading: 1178).

The Ontario Drive Clean pamphlet states for "High NOx on Driving Test" the possible causes:

* Inoperative/ineffective exhaust gas recirculation (EGR) system
* Excessively lean air/fuel ratio
* Malfunctioning or missing catalytic converter (3-way catalyst only)
* Excessive spark advance
* Faulty Thermostatic Air Cleaner system
* Engine deposits or mechanical defect
* Faulty cooling system

A little insight into my vehicle's current condition:

* When i cold start or even warm start for the most part the car will ride rough to idle then shut-off after a few seconds. Turning it back on and giving it gas makes it eventually hold idle ok.

* The rear muffler is in rough shape though I've patched it with some foil and muffler cement :)

* The catalytic converter is fairly rusty but doesnt appear to have any holes though the piping entering into it had a couple tiny fractures which i used foil and cement to plaster over.

* When driving the car and waiting at a light it runs fine and mostly doesnt threaten to shut off.

* Last year i replaced all the spark plugs and distributor cap/rotor.

* The fuel filter possibly has never been changed on the vehicle since its purchase back in 1993?

* We consistently drive the vehicle with a very low gas tank and have ONLY ever used Regular Unleaded.

* I went to a mechanic before the E-Test to do an oil change and he said from the sound of the car and such he would guess the EGR Valve could be an issue but he was also a bit concerned about the small fractures just before the cat converter.


What is the most cost-effective way for me to approach getting my vehicle up to standards to pass the E-Test "High NOx"? Can i simply CHECK / CLEAN my EGR Valve and perform some in-house NOx test to confirm?

Is the $150 Canadian Tires diagnosis worth looking into to determine the exact issue(s)?
31 replies
[OP]
Sr. Member
Apr 29, 2010
665 posts
24 upvotes
London
WRT the EGR Valve, there appears to be one vacuum hose coming from the side and 2 nuts near the base. There is also some large piping that attaches / screws into it near the base. I'm going to try removing the EGR by first removing the single tiny hose then unscrewing the nuts and hopefully the whole thing slides out. I will then proceed to clean the innards with some solution and reinstall? Can the gasket be re-used?
Deal Expert
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May 10, 2005
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You have a 20 year old 4 cylinder car. By your own admissions, there has been a lack of maintenance and, it does have issues.
No way around it, you are going to have to pay to have it fixed. What need to be fixed? Well, that has to be proprerly diagnosed. No sense going at it on a hit and miss procedure. Where to have it diagnosed? Well, I would not take it to a Canadian Tire shop but rather to a shop that specializes in Mercedes or European cars. They would have the tools and rest equipment needed for your car.
Or pay the repair cost limit and get a 2 year exemption.
Deal Fanatic
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Mar 5, 2006
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Murica
my dad's car recently passed e-test after failing NOx, passed everything with flying colours, mind you it was an integra. When we took it to a honda mechanic, they said it was the cat for sure. Got it changed and warmed up the cat by driving on the hwy for 10 km and tested at the same e-test shop. Bam. passed.

from your description, it sounds like you may need a tuneup, involving cleaning out the cold start valve. Checking and cleaning EGR valve and it's hoses to make sure you're getting vacuum.

you do not need to replace the sparks/cables/distr caps/rotors.
Take out your spark plug and see what color are the head. If its black, it's too rich, too much carbon buildup. If it's got a glaze look, it's too lean.

you shouldn't be driving with low levels of petrol, as the fuel pump would be consistently at high temps, leading to failure. The pump uses petrol as a coolant while submerged in the tank. Low levels mean impurities at the bottom of the tank means high concentrations gets sucked into the engine.
you should drive with at least half tank. I refill at 1/4 tank level. Summers I fill up to 3/4 mark. Winters I keep full tank.

fuel filter symptoms would arise when your engine misfires at higher revs.

Your muffler is in bad shape, but is there leaks?
If not, don't worry, just exhaust sounds bad.
I'd say it's your cat.

Never bring it to cdn tire. You should bring your car to a MB specialist, they would be familiar with the cars and symptoms and solutions.
Deal Guru
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Nov 21, 2009
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1. fill it with premium
2. do 10-20km on a highway just before the test
3. take it to oil changers
it worked for me
Deal Fanatic
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Mar 5, 2006
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Murica
vero95 wrote:
Jul 23rd, 2010 10:03 am
1. fill it with premium
2. do 10-20km on a highway just before the test
3. take it to oil changers
it worked for me
no, don't do that.
I tried that for my dad's teg.
I filled it up and drove it to Bradford and back in the wee hours.
Still failed.
All you need is a good 15-20 km run at various rpms. The engine will be nicely warm.
issue isn't about bad gas.

Get it looked by a merc mechanic.
For us, it was the cat. GL op
Deal Expert
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Jan 27, 2006
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vero95 wrote:
Jul 23rd, 2010 10:03 am
1. fill it with premium
2. do 10-20km on a highway just before the test
3. take it to oil changers
it worked for me
+1

It worked for me on my last coupe. Ripped it along 410 from Bovaird to Steeles, on my way back got off Queen Street and went to Firestone shop.

I remember why I failed my first E-Test, I got it done at Canadian Tire. :twisted:
"I'll put up color bars before I'll put you in front of our cameras."

- MacKenzie
THE NEWSROOM (HBO)
Sr. Member
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Jul 12, 2005
694 posts
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Running too rich,
if you can detune the care and bring it to a few degrees below regular idle might work, I have to detune my car everytime i go for emissions
[OP]
Sr. Member
Apr 29, 2010
665 posts
24 upvotes
London
DJSINR wrote:
Jul 23rd, 2010 1:21 pm
Running too rich,
if you can detune the care and bring it to a few degrees below regular idle might work, I have to detune my car everytime i go for emissions
FOr my 1991 Mercedes 190E, how exactly would i go about "detuning" the car? Sounds interesting. Just for the record a cold start and sometimes warm starts still cause the car to bump and stall however while at red lights it almost always is fine.
Deal Addict
Jan 22, 2004
3168 posts
36 upvotes
Toronto
DJSINR wrote:
Jul 23rd, 2010 1:21 pm
Running too rich,
if you can detune the care and bring it to a few degrees below regular idle might work, I have to detune my car everytime i go for emissions
Its the opposite, running too lean will cause NOx situation.
Deal Addict
Jan 22, 2004
3168 posts
36 upvotes
Toronto
Your drivability problems should not be related to the NOx problem.

You could clean the EGR to make sure there is no restriction or clogging of waste gas flow. Also you should verify the operation of the valve. Valve should move when enough vacuum is applied.

For the EGR in my car I can manually push the diaphragm and cause the engine rpm to fall. This would verify the flow. Then after car is warmed up, I can apply gas and can feel the diaphragm move. This would verify the EGR functionality.

Another possible component would be the cat. But I think if the EGR is operating at spec, NOx should be within limit even you have a less than ideal cat. Given your HC and CO is within limit, I would hesitate in replacing the cat.

If you have access to change the ignition, retarding it will help reduce NOx.

There is no easy way you can verify NOx at home. You need their emission test machine.

I think the re-test is half price.
Member
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Mar 7, 2010
368 posts
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Toronto
Sounds like it may be a partially plugged injector, fouled up valves or possible sticky/dirty egr valve ports.

If you don't want to part with the diagnosis cost (recommended) then go get a professional injector flush & fuel system cleaning. then fill up with high octone Sunoco gas and take it for a good run to clean it out. A good run means high revs to help purge the bad collection of gunk and help to clean out the cat. Then return for a half price retest.

I suggest this because it is always helpful to get this done every few years and it doesn't involve replacing any parts that might still be properly functioning, but just lazy.

Good luck on getting her to pass!
Deal Expert
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May 10, 2005
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Ottawa
DJSINR wrote:
Jul 23rd, 2010 1:21 pm
Running too rich,
if you can detune the care and bring it to a few degrees below regular idle might work, I have to detune my car everytime i go for emissions
What you say makes absolutely no sense at all. By changing the timing, especially a few more degrees below top dead center will only ensure you get even less "burn" of the injected fuel mixture. If, in fact, you do this every time you go for a test, then the rest of the time your car is running extremely inefficiently, poor performance and, not optimal fuel economy.
Newbie
Jun 21, 2005
63 posts
3 upvotes
pay the tester a nice tip to test your car in first gear hehehe, most know how to do it
Member
Jul 22, 2009
331 posts
27 upvotes
TheOneDealer wrote:
Jul 25th, 2010 3:16 pm
pay the tester a nice tip to test your car in first gear hehehe, most know how to do it
+1
everyone knows the method but no one knows which shop to go
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