Emissions problem

[Warduke]

I went to get an inspection today and they said my car failed emissions and it smelled very strong in the shop after they did the test. The shop owner said it could be my cats or a o2 sensor. My quesion is wouldnt the check engine light come on if it were one of those components that were faulty? What else should I look at or how should I trouble shoot this problem? This is a 3.0 SHO with 150k on the clock. Previous owner claims he recently replaced the exaust and while he was at it replaced the cats with high flow cats. Im not sure if he was being honest or not or how I can tell.

 

[sdpatt]

Regarding the O2 or other sensors, run the KOEO test. To see if the cats are higher flow cats, look at the piping size at the inlet and outlet of the cats. If the piping is larger diameter than the rest of the tubing they are likely higher flow cats. It usually doesn't cost any more to put on cats for a Mustang than cats for the original size pipes. That's what I do.

 

[doclees]

I think I read pulling the SPROUT(?) plug might help you pass your e-test in the mean time.

 

[sdpatt]

I think I read pulling the SPROUT(?) plug might help you pass your e-test in the mean time.

Pulling the SPOUT shorting plug near the CID sensor will only help in the reduction of NOx generation. This is due to the 3.0L SHO engine being designed before the time when the NOx emissions were monitored. The NOx components are created by high combustion temperatures that are the result of high compression engines. The standard industry fix is to recirculate oxygen and HC-depleted exhaust gas into the intake manifold to reduce the combustion temperatures. That job is the function of the exhaust gas recirculation (EGR) system which is not part of the 49-state 3.0L SHO engine.

What were the measured amounts of the emissions components? Depending on whether it was the HC, CO or NOx component that was high can help locate the source of the problem.