> I was helping a friend tune-up his TR6 today and we got dry compression
> readings of 120, 122, 120, 118, 115, 130 for cylinders 1-6. It ran fine
> (decent pull through all gears) but we couldn't get the CO to
> come close to
> passing emissions (need < 4%). It was reading over 19% on the CO
> monitor. No
> amount of adjusting the fuel mixture and/or timing would get it any lower.
Bud, as Steven said, high CO is almost always a rich mixture. As you lean
the mixture, the CO will drop and eventually the HC will rise as the engine
starts misfiring due to lean mixture. Those compression figures only show a
variation of +/- 7%, which while not perfect, shouldn't cause it to flunk
smog.
Does the car perhaps have a non-standard fuel pump ? High fuel pressure
might be the problem. Also check what happens if the vacuum line to the
carbon canister is disconnected and plugged. I once had an engine flunk
because the carbon was saturated in fuel, the engine was going rich at idle
on the fumes sucked out of the carbon. If all else fails, try lowering the
float level by 1/4" or so and try again.
You might also double check the cam timing. I've seen a "slipped tooth" cam
timing cause mysterious rich mixtures. Likewise, 'wild' cam grinds or bad
valve adjustments can cause rich mixture.
Randall
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