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Forum > Failed Smog Test > Question

1993 Ford Probe Failed NOx Running Lean

My 1993 Ford Probe 2.0 4 cylinder car failed the smog check because NOx part level was too high and the smog technician stated I'm running lean

I was wondering if you could help me find out why my car is failing emissions. It is failing the NO levels part only and there was a check engine light on for a little while for the intake air temp sensor and the EGR valve sensor and fuel pressure regulator solenoid.

I replaced the vacuum lines to the EGR because I found out they were really bad and the EGR trouble code went away. The fuel pressure regulator solenoid is a part that I can't seem to find anywhere. I am wondering what are your thoughts on what I should do? I have no more check engine codes showing up but I'm still not sure it will pass the emissions test and don't want to waste more money on it.


Answer:

If you've scanned your Ford Probe's ECU after replacing the EGR vacuum lines and the intake Air Temperature (IAT) sensor, and no trouble codes appear, we can recommend you go ahead with the smog check to find out the new results of the test; hopefully they will be passing.

Having repaired the EGR vacuum lines more than likely got the EGR valve working again, and subsequently lowered (will lower) NOx emissions during the smog test, and thereafter.

As far as the Fuel Pressure Regulator Solenoid, should you need to replace this part, and you might not need to since it seems there is no longer a trouble code appearing for it, is located right next to the throttle position sensor (TPS). The TPS is attached to the intake manifold exactly where the intake air unit's duct is attached to the intake manifold pentium. The FPRS should have a black cap on one end and two vacuum hoses attached; one on its side and one on its bottom. This solenoid is crucial to the proper operation of the fuel pressure regulator, and the fuel pressure regulator is crucial to proper are/fuel mixture.

If after the next smog test your Ford Probe still fails the smog test for high NOx, we'd recommend checking fuel pressure, the fuel pressure valve itself, and the fuel pressure valve solenoid for proper operation.


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