Emissions Trouble

[CrankShaftKid]

Having a hell of a time getting my emissions to pass inspection.

 

First time I took it in, failed. Realized the PO took the dam the cat off. Okay so I take it in and get a cat installed.

 

Took it in today, hydrocarbons are good, but Nox is way high. Actually 4 times higher than pre cat, which really doesnt make sense.

 

 

Assuming the guy didnt screw up the second time and I do in fact need to get Nox down, where should I start?

 

 

Thanks guys

[87ComancheLB]

O2 sensor my guess.

[my87manche]

check EGR. nox caused by excessive combustion temps. EGR sends exhaust gases in to lower temps and nox.

[CrankShaftKid]

Thanks guys, changed the EGR and 02 and am now compliant. Throttle response is much more lively as well.

[FxRacing282]

also when you go to test your engine you want it real hot and whatnot. when the engine is just slowly driven to the garage it has less of a chance of failing.

but it looks like you are all set