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Don't worry about the vacuum lines, that would lead to a lean mixture, high CO points to a rich mixture. Here are some things to look for
CO Failures (fuel injected vehicles)
Engine not at operating temperature. Example, engine/cat cooled off while waiting in test line or has a stuck open or missing thermostat.
Ruptured or sticking canister purge valve.
PCV plugged or drawing in fuel contaminated oil vapors.
Malfunctioning computer inputs. Example: Defective O2 sensor, reading lean all the time. Clogged or broken MAP sensor vacuum hose (reading a heavy load all the time). Coolant temperature sensor having high resistance or open circuit (reading "cold engine" all the time). Throttle position sensor stuck or open ground, (reading wide open throttle).
Contaminated, restricted or bad catalytic converter.
Leaking or bad injectors.
Mass Air Flow sensors (voltage or frequency being too high).
Fuel pressure too high (restricted fuel return line or stuck fuel regulator)
Ruptured fuel regulator (fuel leaking directly into intake)
Your CO2 reading is too low? Could be the CAT is bad (isn't converting HC to CO2 efficiently), must be checked with a 4-gas analyzer.
'94 945T (daughter co-opted it for college, used to be mine)
'99 S80 (mom-in-law's)
'88 240DL (son's)
'84 242Ti (future commuter)
'89 560SL (wifemobile)
'88 300TE (my commuter, for sale)
'68 GT500KR (under restoration)
--
Bob K
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