Mechanics

EMISSIONS

1992 Nissan Pathfinder

Engine Performance problem
1992 Nissan Pathfinder 6 cyl Four Wheel Drive Manual

i recently went to do a pretest on my 1992 nissan pathfinder, it didnt pass, technician said it was due to high emissions. Technician also said to fix oxygen sensor, catalytic converter, and egr system, he wanted $450. Do I need to fix all these parts. HC measured at 119 at 15mph 26 at 25mph. Co measured at.69 at 15mph.09 at 25mph. NO measured 2684 at 15mph 1265 at 25 mph. Emissions test results GROSS POLLUTER. Can someone help thanks.
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Alfredv85
April 19, 2010.



Hello alfredv85

Yes you need to fix them and your tech. Is right on track.
Hydrocarbons (HC) are basically unburned fuel molecules.
Normal engine out or pre-converter hydrocarbon levels should be less than 300 parts per million. The catalytic converter should be capable of lower this level close to zero.(Yours is 119 at 15mph 26 at 25mph)
If there is more than 300 parts million, mean there is a problem and anything that inhibits proper combustion in the engine can raise HC. Such as dead oxygen sensor, EGR system, vacuum leak, fuel injectors problem, over advance ignition timing.

When it come to your CO
Normal engine out CO levels should be less than.75 % and the catalytic converter should lower this amount to almost zero(yours is.69@15mph and.09 at 25mph)again, catalytic converter may be the problem but also high fuel pressure caused by a bad regulator, or leaking injectors or any sensor input that have an effect on fuel delivery system such as oxygen sensor, coolant or air intake temperatures senors, MAP senor, TP sensor.

The Oxides of nitrogen should be below 1000 ppm(your is 2684 at 15mph 1265 at 25 mph)
This is the job of the EGR and a bad EGR can act as vacuum leak.

Tiny
Mathiaso
Apr 22, 2010.