1987 Honda Prelude Failed Emissions

SEPHRON1

MEMBER
1987 HONDA PRELUDE
4 CYL
2WD
MANUAL
199,000 MILES

We took our car in to get emissions tested and it failed the CO emissions at 7% but was fine on the HC. So we had diagnostics run on it and they replaced the O2 sensor but it still failed the CO emissions with 6%. The catalytic converter is fine and we recently had the oil changed, but not the air filter. Will changing the air filter and putting engine cleaner and premium help it pass? Is there anything else we can do its the only car we have?

1 Reply

KHLOW2008

MECHANIC
41,814 POSTS

Hi sephron1,

If the air cleaner is badly clogged, replacing it would help.

Here are some comments that you can consider.

Clean the EGR system.

If the vehicle had been driven slow most of the time, perform some hard driving, ie race the engine with some hard acceleration. This would help clear out some carbons.

Check spark plugs for fouling and gapping.

Check valve clearances.

Check ignition timng.

Some fuel cleaner and premium should help.

If all else fails, the last resort would be to replace the catalytic converter. It is not performing as well as it should.