emission HC failure ???

[jimsho95]

hello, Does anybody have any ideas on why my 95 ATX 112,000mi is failing state emission Hydrocarbons. CO's are fine. I am getting no codes but tailpipes are abit black as if its running rich, but car runs fine.if anybody has any suggestion,please let me know. thanks from stranded {state e-check} SHO owner.

 

[SHOnuff93]

some people with EGR equipped cars have experienced the same thing here in Cali. Things to check include bad o2 sensors, and make sure there is no leak in the EGR tube.

 

[projectSHO89]

jimsho95:
hello, Does anybody have any ideas on why my 95 ATX 112,000mi is failing state emission Hydrocarbons. CO's are fine. I am getting no codes but tailpipes are abit black as if its running rich, but car runs fine.if anybody has any suggestion,please let me know. thanks from stranded {state e-check} SHO owner.

EGR problems usually cause high NOX readings, not HC.

High HC readings are normally from a too-rich mixture.

Common reasons are the engine is running too cold due to thermostat/ECT concerns or worn out O2 sensors.

Steve

 

[Zap]

I see that you're subject to e-check here in Ohio. Unfortunately neither of the SHOs here are required to pass it, because they are both registered in Columbus, but whereabouts are you in Ohio? Since you don't see any codes, it is possible that you are running rich. However, both of our SHO pipes have a bit of soot, but are running well. Where does your temp gauge usually sit when driving? If it is below the NORMAL, or by the blue line or C, you are probably running stuck in the "cold loop" which will definitely make the SHO run rich and cause a problem.

<small>[ March 02, 2004, 11:37 PM: Message edited by: Zap ]</small>

 

[sdpatt]

Try reading up on how the various emissions components are created at this link. Excess HC means that some unburned fuel is getting past the catalytic converters. There are several possible causes from incomplete combuston due to bad spark plugs or plug wires to incomplete converter oxidation due to a silicone contaminated catalyst. It could be as simple as old, slow switching oxygen sensors and only a complete examination can locate the cause.

 

[jimsho95]

temp seems to be in the middle of the normal, and my NOX are also over emission limits along with HC. i did find oil in some of the plug wells but didnt seem to effect performance yet. as to ZAPs question i am just east of Akron, OH {kent}