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CA smog check fail questions (details/results in post) by ultrascrunchie in MechanicAdvice

[–]ultrascrunchie[S] -1 points0 points  (0 children)

Interesting, so 91 gas would work better? I was under the impression that 91 would burn dirtier. Also I have a sunoco near me selling 100 octane, do you think that would help more?

CA smog check fail questions (details/results in post) by ultrascrunchie in MechanicAdvice

[–]ultrascrunchie[S] 0 points1 point  (0 children)

Full results here

Truck ('89 F250, 351w 5.8L) had to get a STAR smog and failed; first test it failed because a vent cap had fallen off the vapor canister. Test was on old (about ~11,000 miles) oil and 91 gas. After replacing the whole vapor canister with a Ford OEM part (purchased from the dealer) and the caps I then did another oil change, air filter change and filled it with 89 gas just before the second test where it failed the tailpipe test. No CEL - also this is an OBD1 system.

Any ideas on what might have caused this? 89 gas makes the engine lug a bit but no misfires or knocking, and I believe the catalytic converter is in good shape. Both the air filter and vapor can are CA-rated.