Gary Briggs

I failed a smog check ever so slightly! My low speed NO levels were to high, but they passed with flying colors at the higher speed!



I called my mechanic, who also owns a jeep cherokee, he seems to think its running a bit lean at that speed, causing excessive temps.

My jeep is stock with the exception of bosch 715 injectors, it has a brand new cat installed prior to the test!

Thanks in advance for any help!!

Gary Briggs

nobody has any insight?

bloddy mud

Sorry don't know any thing bout smog tests. Hang in there for a chime. It's probably a stupid o2 sensor problem or a evap bs

Bustedback

I would look for a vacuum leak.

Radi

What do you have for fuel pressure...and is it an OEM cat or aftermarket?

Gary Briggs

It's a OEM direct fit cat, I can't find a vacuum leak, that's not to say there isn't any!

NorCalJeep

Did you replace the O2s when you replaced cat?

Gary Briggs

I didn't replace any, how many are there?

black2000xj

should be 2 - upstream and down stream

i heard cali jeeps have 4...but i dont know for sure on that

Gary Briggs

According to my mechanic buddy it's not the sensors, because it only failed the low speed NO test and passed the higher speed. He says he thinks at the lower speed its becoming lean.

Gary Briggs

whats an easy way to richen up my mixture, thats whats cause the excessive NOX, a bit lean resulting in high combustion temps.

Bustedback

There is no mixture adjustment that can be made, it's all handled by the ECM.

F1Addict

I still think it's an O2 sensor.

ZINGGG

I would agree

Gary Briggs

wouldnt it fail both the low speed and the higher speed tests if the o2 sensor was bad?

I put a new cap and rotor since it was due for one, chased down a couple of exhaust leaks, ran some sea foam through and am still getting virtually the same results, ive tested 3 times now, all 3 tests failing only the low speed NOX.

Ive been told if the sensors were bad you would fail both low and high since it would creat a lean condition at both speed not just the 15mph!