Helping a friend with his '93 Protege (1.8l, EFI, SOHC, auto) - it blows a bit of blue when cold, then once it warms up it spews a lot of black smoke when he hits the gas. Driving behind him, I don't smell any burning oil, it just smells like it's running REALLY rich. Hydrocarbon reading on emissions test is 'way up, all other readings are well within spec.
I suspect the O2 sensor is bad, possibly clogged with burned oil, and causing it to run extra rich... is anyone familiar with O2 sensor operation on these cars, and thinks this might be likely? Is there any simple way (DMM or something) to test that the O2 sensor is working at all? I was quoted $80+ for a replacement, so it's not something I want to just swap out to "see if that might be problem."
A mechanic suggested a clogged catalytic converter as a culprit in the increased HC reading and figured new plugs might help, but neither explains it running so hideously rich.
I know plugging in a diagnostic computer is the best idea, but that would be another $60-$80 at all the shops he's asked at so far. I'm not even so concerned with getting the thing perfect right now (he's got a tight budget and a baby due in a month), just need to get it past the emissions test (one reading was .9-something, another was .544, pass is .500!)
Any help/info greatly appreciated.