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Help...poor performance and low fuel economy


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Hello...new to your forum...thanks in advance for all of your insight. I have a '98 Civic HX, it's a D16Y5 VTEC-E. I have stumble/hesitation on acceleration, and I'm getting only about 15 MPG, although that's harsh summer city driving. I got close to 30 MPG in the past. I had changed my timing belt and H2O pump near the time this started, I made double sure the valve timing was correct (& not off 1 tooth). Its ignition timing, on the other hand, needed to be adjusted from about the middle of the distributors range of rotation, to nearly all the way toward the front of the car. This was many months post timing belt change, but it is timed now. Other things I have done:


-New cap/rotor/plug wires/plugs (gapped, but I skimped and bought autolite plugs)

-New OEM pre-cat ("broadband") and post-cat O2 sensors (when it was throwing code p1167 6-months ago)

-New air and fuel filters

-Oil/oil filter/PCV valve change

-It does have 190k miles and uses 2 quarts oil a month, but its compression is good in all 4 cylinders to this day

-Its oil, however, would turn dark black in just a matter of days after an oil change

-Cleaned it's intake/throttle body with Chemtool



Where I am at now is speculating its catalytic converter (??) When I shine an IR thermometer on the precat exhaust pipe (not flange) I get about 350 deg. F. Postcat the exhaust temp is lower at about 250 deg. I see descriptions of every other temperature configuration scenario, except mine. How should I proceed? If it is the catalytic converter, does anyone have advice on replacement? Could I get by spending less on one than OEM?


Thanks for any help...

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A common symptom of a clogged catalytic convertor will be that the car idles or even cruises steadily but then when the accelerator is depressed it bogs down. Usually the problem is more pronounced when the engine (and convertor) heat up to full operating temp.


Even at 30mpg something is amiss. With a mindful eye and foot that HX should easily be bumping 40's provided you are doing at least 50/50 city/hwy.

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