Hi All,

I started to get this code "P0444 -- ECM-421C -- Evaporative emission system (EVAP) valve -- Signal too high" the other week. A few days after, the car started idling low (~650rpm) and would shudder or stall when revved (does not go back to idle without some hesitation). If I reset the code, everything is OK for a while (a few days). Even stranger: the code comes back almost immediately, but at first the engine behaves normally; however a few days later the low idle comes back. Any ideas?

Thanks All

 

My guess? it's the Evaporative emission system (EVAP) valve.

 

Thanks Hudini. Will get it checked out. Just curious (for my own knowledge), how it is linked to the reset of the codes? Howcome it will self-correct then eventually get bad again? Does the ECU adjust the idle after some time with the code on? Thanks