i got 91 civic sedan stock.my car won't pass IM.i try to take it in to a shop.everything is good on the car..no cel.it start rite up idle pretty smooth.the thing is it wont passed.the reading was due to excesive carbon coming out tailpipe.i might need lil tune-up like oil change,valve seal.thats pretty much it...any help is appreciated really need to pass...thanks

 

ok try doing a tune up like everything plugs,wires, cap n rotor, pcv, fuel filter, air, oil and filter. and pump regular gas dont pump 91 it will make you fail. if it still passes you probably have a bad o2 sensor or cat. if ur engine has an egr valve thats mostlikly making you fail

 

only thing imma have prob is probably with fuel filter and cap rotor?others are piece of cake.if the cat or o2 are bad?why dont it throw a cel??just did a fresh oil change and i rev it up i can smell lil unburnt fuel coming out the tailpipe?

 

You mean excessive HYDRO-CARBONS/HC?

What are the rest of your readings from your smog test? HC, CO, CO2, O2, NOx? All are valuable readings and relate to each other.

 

thats the only thing it did'nt pass.imma try to do some tune-up and let yall know 'what it is'.

 

Tune it up. If it still doesn't pass - check your cat. My 90 wagon was running great but failed for HCs. My converter was a mess - melted and plugged - new converter fixed the problem. I never had CEL or codes.

You get no codes because these are not OBD0II cars - minimal diagnostics.

 

this wont fix the problem but you can hide it so you can get your sticker and have time to spend on the proper repair

run your tank down to less than 1/4 tank.
pour 1gal denatured alcohol in the tank
drive to test center in low gear, at least 10mi (keep revs high to get your cat as hot as possible)
take test

then go to gas station and fill up the tank


I had to do this 2yrs ago after I failed miserably, worked like a charm

turned out it was all because I had not insulated my new header at the time and my cat was cold

contrary to the myths that I am sure we will hear about, the alcohol does not hurt your engine, lines, or pump. Especially since you dilute it with gas immediately following passing the test.
I have had no ill effects from it, same pump, no clogged filter, no busted injector, just passed the smog test

 

if im not mistaking ur draving a car with obd0. when i failed my first time it was for bad cat and o2 sensor. obd0 will throw stupid codes like tem sensor so n so or something about ur speed sensor but it wont catch o2 or cat.

or also ur car might be oout of timing
little things like these will make you fail and like i said earlyer dont pump 91 if ur car doesnt require it. ur car will not be able to completly burn the gas

 

find a buddy that will let you borrow a good working cat do a full tune up like stated above and make sure your car is timed properly i would do this first before trying a new o2 high hc mean that you are either not burning your fuel correctly which turns to co2 and h2o mostly related to your ignition system if u had the actual numbers to post it would help out