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Jared D
Jared D, ASE Certified Technician
Category: Nissan
Satisfied Customers: 1448
Experience:  Shop Supervisor at County Fleet
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My 92 Path (298K mi) has failed GA emissions the last 2 yrs,

Customer Question

My 92 Path (298K mi) has failed GA emissions the last 2 yrs, even after $850 and $1150 in repairs, including replacing the cat, 02 sensor, major tune (new distrib, plugs, wires), fuel injector cleaning (and I'm probably forgetting something) and cans of Sea Foam. Care to take a stab at a solution?
Bobby L.
Submitted: 1 year ago.
Category: Nissan
Expert:  Jared D replied 1 year ago.

I'd love to help.

Do they tell you what it is failing for on the test?

Hydrocarbons, HC?

Carbon monoxide, CO?

Oxides of Nitrogen, NoX?

In my state we test for these three gasses and a failure in one or the other helps indicate where the problem is.

Customer: replied 1 year ago.
They do but I didn't keep the results printout from last year and haven't yet tested for this year.
Expert:  Jared D replied 1 year ago.

Ok. Well how would you like to proceed? I can give you some pointers about what causes high numbers in each category if you would like. Do you plan to have it tested soon?

Customer: replied 1 year ago.
I have to test by the end of the month but I'm trying to get a lay of the land in terms of expenses expectation. There were a lot of dollars spent on trail and error the last two years but never got a repair resolution, rather I was granted a waiver based on dollars spent. What say you?
Expert:  Jared D replied 1 year ago.

It's hard to say without knowing why it failing, but here are some basic pointers:

Hydrocarbons are un-burned fuel. If you have replaced plugs, wires, cap rotors, etc, that will usually solve the hydrocarbon issue. Leaky fuel injectors can also cause high hydrocarbons on this model and the fuel injectors and fuel pressure regulator can be replaced to fix it.

Carbon monoxide is caused by poor fuel mixture and poor catalytic converter function. Again- it seems like you have already changed the cat and o2 sensors.

NoX is caused by a mixture of both hydrocarbons and carbon monoxide changing into oxides of nitrogen. The best way to reduce Nox is the ensure a proper fuel mixture, and to check the EGR system for restrictions. A restricted EGR will cause excess NoX production and foul the catalytic converters. You should also check for a faulty EGR back pressure transducer BPT.

Which of these systems do you want to check into first? I can send some diagrams if you plan to tackle it yourself.

Customer: replied 1 year ago.
Will the test be effected by exhaust pipe/muffler issues?
Expert:  Jared D replied 1 year ago.

I can't say for certain because I don't know what they test for in your area, but here in my state, if there is a hole in the exhaust system it can still be tested, but might fail for poor sample conditions because of the hole. Basically the emissions machine detects that there is air in the exhaust system diluting the test sample from the exhaust leak.

What sort of pipe/muffler issues do you have?

Expert:  Jared D replied 1 year ago.

I just wanted to check in and see if you needed any additional information. I hope that I have been of some assistance and would appreciate a positive rating if it have. Thanks!

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