I have a diagnostic question about emissions. My 79 f100 is exempt but my 88 Mazda B2200 isnlt. I know it was running a little lean (which I have since corrected) but my HC and CO readings are waaaaay high (NO passed). As the shop where I got the test done would offer no advice (without a further $100 diagnostic test)Iwas hoping someone with a lot more knowledge in this field could advise me of where to look for the cause. I get two re-tests @ $17 and would rather put my money in the the probable sensors/causes and see how I fare.

Thanks in advance

 

high HC and CO is from unburnt fuel and lousy combustion. I think your on the rich side now. Doesn't the o2 sensor control fuel mixture? I'm into old stuff mostly, but I'm pretty sure my buddy's car was running rich until we cleaned out the o2 sensor and the map sensor.

 

If it uses Ford's EFI system, try pulling the vacuum hose from the Fuel Pressure Regulator to see if it's leaking gas. You can pull the codes yourself free anytime you feel like it and have a paperclip handy. The MAP sensor & TPS are also likely suspects of a rich condition, but another KEY to passing is KEEP THE ENGINE RUNNING & HOT while you're waiting for your test.