## FAILED SMOG again ## - Benzworld.org

hifeverz · 05-24-2006, 07:38 AM

1990 300SL 151k miles

Fixes: New spark plugs, new wires, new air filter
Prior to smog test drove car approx. 30miles at hiway speed.

I've failed the smog again. The results are as follows:

HC(ppm)
15mph: MAX=102, Measured=130 > FAILED

25mph: MAX=77, Measured=96 > FAILED

CO(%)
15mph: MAX=0.68, Measured=0.07 > PASSED

25mph: MAX=0.55, Measured=0.09 > PASSED

NO(ppm)
15mph: MAX=748, Measured=141 > PASSED

25mph: MAX=687, Measured=113 > PASSED

Any simple DIY suggestions?? What can I do before I retest?? Could it be O2 sensor?? Fuel enrichment adjustment? OR????

I need your expert help out there before I get to a shop jock who'll charge a small fortune.

Thanks,
Hz

lnguyenh · 05-24-2006, 08:36 AM

your engine failed on the third cycle which is the combustion. Your combustion is likely incomplete. This could be the result of many things like piston rings (leaks), spark plugs, gas octane ... causing the engine misfired.

When the fuel is not burn completely, it produces high HC.

Oh, also look for intake air system (for leaking).