Finally I get to feel like I'm adding to this forum instead of just taking ! Last month my CEL came on and it coded EVAP system. I did a handful of things, cleaned the IAC and did a SeaFoam treatment reset the CEL and it would come back on in in a day or so, again with the EVAP system. THEN the beast started missing. Pulled the codes and COPs 2 & 6 are mis-firing. Changed the COPs, reset the CEL and now all is good in the world, no CEL, no mis-fires, running like new with all most 200,000 miles on it. EVAP system IS FINE !

For the Newbies like me, CEL = Check Engine Light and COP = is Coil on Plug.

 

Good for you! You may soon be a certified DIYer.

 

What was the specific EVAP code that turned the CEL on?

(I'm trying to imagine what effect the #2 and #6 COP would have on the EVAP system )

 

I don't remember the code number, 0446 maybe ??? The scanner tool said EVAP system. Bought a new gas cap per the AutoZone dude and that didn't help. I believe that the COP not firing the plug to it's full capacity was overloading the system with fuel.

 

Note to all - ALWAYS write down any codes for future reference/help.

Not sure how that would trip an EVAP code. Maybe removing the old gas cap and putting a new cap on eventually sealed up the fuel system.

But hey, you DID fix your mis-fires . . .

 

You could've sent money.

 

I hate to be a wet blanket, but there's no way a misfire due to a COP is going to cause an EVAP code. It doesn't work that way. The only thing that would be overloaded with unburned fuel would be the converters. Hopefully, you won't develop cat efficiency codes as a result of the misfires.

The EVAP system test has a stringent set of entry parameters that may keep the test from running for days, weeks, or even months notably including one that requires the temperature be above 50F. Additionally, the test must fail on two consecutive executions to set the MIL and the fault code.

 

P0446 Evaporative Emmission Control System Vent Control Circuit
OBD-II Trouble Code Technical DescriptionEvaporative Emission Control System Vent Control Circuit Malfunction

What does that mean?Evap vent valve has only one purpose. It closes in order to seal the vent so the EVAP system can pressurize and ensure there are no leaks. Evap vent valve is usually supplied Batt. voltage with key on. The ECM's driver controls the ground, and when grounded, activates the valve (closing it). If the ECM detects a short to ground, and open,or a short to battery voltage on the control circuit, P0446 will set. Code also may refer to ECM detecting that EVAP system is unable to achieve or maintain vacuum during test.

SymptomsThere will be no obvious symptoms to driver, other than MIL illumination.

CausesA code P0446 could mean one or more of the following has happened:

Faulty vent valve
Open, short or excessive resistance on Vent valve control circuit
Blockage of vent valve
Bad PCM
Possible SolutionsWith a P0446 OBD-II trouble code, here are some things to try:

Replace Vent valve
Repair open, short, or resistance problem in control circuit
Repair open, or short, or resistance problem in power circuit
Replace PCM
Other EVAP DTCs: P0440 - P0441 - P0442 - P0443 - P0446 - P0453 - P0455 - P0456

 

"notably including one that requires the temperature be above 50F" I live in Florida, it's rare to get BELOW 50F. I was told "the fumes/unburnt fuel would overload the canister and cause the EVAP system to malfunction" also was told if you continue to overfill your fuel tank that could cause the EVAP system to malfunction. Bad COP would cause unburnt fuel to cycle back into the manifold and possibly vaccum lines. Drove the truck for a month with the CEL on with a new gas cap. Have now drove the truck a month with the CEL off AFTER changing the COPS. Say what you like I believe there is a connection.

 

I tried adding to your reputation for this comment but it said "I must spred the love before giving you anymore"

 

Thanks for trying!

 

No, a misfire cannot set an evap code. The system has no way of knowing that a vapor canister is loaded except by off responses to fuel trim, so you can rule out mis-fueling as a possible cause, also. If it could, you would be able to describe the cause and effect and it would be consistent with the manufacturer's data. Otherwise, chalk it up to either coincidence or some "accidental repair".




You didn't give your location, so my comment covers any situation whether it specifically applies to you or not. Someone in Canada would probably see a incomplete for the EVAP monitor until next May.