Infamous P0440, P0441, P0446 EVAP codes

[koopster]

2001 Corolla Has run strong, still great mileage, no running issues, etc UNTIL:
Clutch disc dampener spring mount snapped, allowing spring to enter disc and chewed it up. No biggie- 187K on thr clutch...got my money worth and decided car was good enough to throw a clutch in it.

Mechanic (long time Toyota mech) had the tranny out and a new clutch in right away. Threw some new struts in while it was in the air, off I went.

Right away I noticed slight hesitations off of idle like when it was time to start from a light- reminded me of a clogged fuel filter or bad injector- car was starving for fuel or retarded timing (like a vacuum leak could do). Over 2K though car runs fine-highway speeds at 2800-3K RPM engine doesn't miss a beat. Within 100 miles got a lean burn code with smelly catalytic converter. Also threw a P0440 EVAP Control Malf. & P0441 Purge Flow codes.

Mechanic changed out 02 sensor and cleared codes. Lean Burn never came back. low RPM hesitation and P0440, P0441, & P0446 came back as quick as before. Mechanic said sometimes moving the lines could of disrupted some crap in the lines- time to change the origional charcoal canister and attached purge valves, etc. ($$$) Off I went sure that it is fixed now.

Still the often hesitation to the point the car almost stalls in the intersection- I can save it by pushing the clutch in, bringing the RPMS up a bit then reengaging the clutch. Then the car runs fine, strong, and goes great down the road at highway speeds. The 3 EVAP codes came back as soon as the ECM had a change to finish diagnostics. Mechanic says he does not know as they put a fuel cap in, changed the entire canister/valve assembly, smoke tested for leaks, etc.

I am looking for ideas. I was told there could be a split/broken vent line inside the gas tank? Are there other vacuum valves or something that could be making the engine act funny occassionally at lower RPM that wouldn't activate at higher speeds)

*** At same time the mechanic had unplugged the wire harness from the ECM under the dash to throw away the old alarm system that was plugged in. Did not see that any of the wiring pins were bent, etc.

The car has a bit of money into it now, looks great, doesn't burn a drop of oil, drives great, except for these issues that started after something got disturbed [something during the drop of the tranny for the clutch?]

THX

[105]

I don't see how anything to do with fuel could've been affected. I know the throttle cables and air intake have to be disconnected during this process so something could've been damaged or not hooked back up right.

[koopster]

Thanks for the note. The mechanic just tried the air flow valve next to the air box. No more hesitation. He thinks the valve was malfunctioning, causing to quick of vacuum pressure change, causing the fuel air mixture to be off. We will see if those EVAP codes come back once the EMC retests itself. THe saga continues but at least I am not dying in the middle of an intersection!