On 10 Apr 2004 15:11:35 -0700, ramswaroop@hotmail.com (eswaroop) wrote:

>Badly need help figuring out what is wrong. All this started after a
>valve adjustment which was done improperly, and fixed later by me.

What engine is this? Are you 100% sure valves are OK now?

>Here is what I know till date. The car runs okay for the first 15
>minutes or so and then the performance and mileage drop drastically.
>It seems to limp around even if I floor the pedal.
>
>No CEL codes
>
>The ignition timing advance is 10 degrees during idle ( must be
>between 11 and 13 according to the honda diagnostics unit).

The L4 engine spec is 12°BTDC +/-2° so it's close.

>The spark plugs are blackened (sooty, so rich mixture)
>
>The o2 sensor is shifting between .1 and .89 volts, but quickly enough
>or not - I dont know..
>
>The car revs smoothly, too smoothly than it ever did earlier in fact
>(maybe sign of retarded timing)
>
>I think the exhaust is heating up a lot more than usual (again sign of
>retarded timing?)
>
>Drives okay for around first 15 minutes, then acceleration and
>response declines drastically as I drive longer, mileage also suffers.
>
>What could be wrong??

Is the engine getting up to full operating temp?... maybe think about
changing thermostat anyway?? I believe your car still has separate temp
gauge and ECT sensors so the next thing I'd check is the ECT sensor for
resistance when engine is hot. Other than that it could be a sensor
problem someplace else - TDC, CYP, throttle position, MAP, etc. Start by
checking harnesses and connectors.

Have you checked that the MIL lamp is working at ignition on? The fact
that you're not getting a MIL when the thing is so obviously out of whack
could also mean the ECM is bad.

Rgds, George Macdonald

"Just because they're paranoid doesn't mean you're not psychotic" - Who, me??