Failed Emissions, AGAIN

94RangerVa · Nov 7, 2015

Greetings,

My 1994 4x4, 4L with 5 speed, has 158K miles. It passed a recent safety inspection, but failed the Virginia emissions test because of high NOX. I added "Guaranteed To Pass" to the fuel and took it to the shop for a tune up and complete filter/fluid changed. Also had the O2 sensor and thermostat changed.

Because mine is one of the 94 models that was produced without an EGR valve, the mechanic said the catalytic converter would be the cause of the failure. So I had the complete exhaust system replaced (pipes, muffler, converter).

I took the truck back for a retest today and the truck failed again. In fact, the NOX numbers were actually worse than the 1st test.

The truck still has 1/2 a tank of the gas with the "Guaranteed To Pass" in it. Is this the reason for the 2nd failure? Does this stuff increase the NOX? If so, Ill run it all out and refuel before retesting.

Any thoughts?

Thank you.

Mazda · Nov 7, 2015

The only advice I can give to you is before you take it in again drive at least 30 to 45 minutes before you get to the shop preferably at highway speeds, and call them about 10 minutes before you get there so they can test it as soon as you pull up. Don't let it cool down. I would also try a different shop.

naford · Nov 14, 2015

Won't they give you a waiver if you pay for repairs over a X dollar amount? In Ohio it is 300 dollars with conditions. Check but I did a search and in Virginia it's 780 dollars but there are conditions.

adsm08 · Nov 14, 2015

The cat is supposed to remove all NOX from the exhaust, but if the levels produced are too high then it won't get all of it.

Cats only work above 400*F, so a test done on a cold system will have higher than normal NOX. NOX is only produced above 1500* combustion temp though, so running lean makes higher NOX. Fuel additives could also do that. I'd run the rest of that stuff out and try to richen the mix if you can.

kimcrwbr1 · Nov 14, 2015

In WA you can get the waiver but you have to give the money to a state emission approved shop. If you buy the parts and put them in yourself it dont count toward the waiver. Is the muffler shop state approved?

Andy D · Nov 15, 2015

Are the O2 sensors working? Hook up a meter and watch the voltage. A working O2 sensor should dither between .2 and .9 VDC below .45 and above .55. It has to be in constant motion within the range. If it parks on a voltage, then it is no good. If you pull the dip stick, volts will go low. Put it back in and pull the vacuum hose to the fuel pressure regulator to make it run rich .8 or .9.

Ok, that was the drill for my '88 528e. I don't have to pass emissions in MA. They only test OBD2 If the FPR is someplace hard to get, try blocking off the air to intake instead. At the time I had flunked for NOx and an OEM BMW sensor was 110$, so I was testing the bee-geezus out of the O2 sensor before I gave up on it.

Just had a wild guess. Was the Y pipe replaced? If so, the O2 sensors were messed with. They are a PITA to find their harness connections behind the engine. I very carefully unplugged them, when I had the pipe out. 21 yr old wiring is very brittle, it may have been damaged.

94RangerVa · Nov 20, 2015

So it seems that the garage installed the wrong type of catalytic converter. There are different types for ERG versus non-ERG system equipped trucks.

A new catalytic converter, this one designed for non-ERG system equipped trucks, has resolved the issue. It passed!

Thanks for the feedback everyone.

Mike

ab_slack · Nov 20, 2015

94RangerVa said:
So it seems that the garage installed the wrong type of catalytic converter. There are different types for ERG versus non-ERG system equipped trucks.

A new catalytic converter, this one designed for non-ERG system equipped trucks, has resolved the issue. It passed!

Thanks for the feedback everyone.

Mike

Thanks for the final update.

By the way, on that guaranteed to pass and other fuel additives that help, you got to run a tank thru and it is on the next tank you test.

94RangerVa · Nov 21, 2015

Thanks for the tip.

Happy Thanksgiving.

Failed Emissions, AGAIN

94RangerVa

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Mazda

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naford

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adsm08

Senior Master Grease Monkey

kimcrwbr1

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Andy D

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94RangerVa

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ab_slack

Well-Known Member

94RangerVa

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