Misfiring?

Hi,

For some reason, both of the codes you supplied are not listed for this vehicle. I know a P0455 is a "gross EVAP leak. These are usually easy to find. If the fuel cap is off, the evap canister is damaged or disconnected, or there are hoses disconnected or broken between the fuel tank and the charcoal canister.

Now, the P0456 is identified as a "Very Small EVAP leak." If we have a large leak, I'm not sure why it is showing a small leak too. Are you sure the codes you indicated are correct?

As far as the misfire, chances are you are drawing fresh air into the combustion chamber causing a very leak fuel mixture. Does your scan tool provide live data? If it does, can you tell me what the short-term fuel trims are at operating temperature?

Next, inspect the charcoal canister and hoses to it. It is located near the fuel tank. See pic below.

Let me know what you find.

Joe

See pic below.

I may not have listed the codes correctly. I do know the first code was for a small leak. The second code was for evap vent valve. When I go into diagnostics it says excessive vacuum. I have to drive 40 miles to work so I will list the short- and long-term fuel specs in an hour or so.

In park with engine at idle short term fuel trim is going from -2.3% up to 2.3%. it doesn't stay steady on any given number. Long term fuel trim is going from 16.4 % up to 18.8%. Most of the time it stays on 17.2%. Engine rpms are all over the place from 690 up to 744. Ignition timing advance is going from 18.5 deg up to 20 deg. Also, the evap system leak test failed. I think the codes were p0442 and p0446. They occurred separately.

Hi,

Okay, it makes sense with those codes. The LTFT are indicating the comp is trying to compensate the air/fuel mixture by adding more fuel. You really don't want that number to be above 10%.

I have a feeling there is a leak at the EVAP vapor canister purge solenoid. That is where I would start.

If you look below, I attached a pic to help locate the part. Confirm the vacuum hoses are connected, not leaking, and not dry rotted.

Let me know what you find.

Take care,

Joe

See pic below.

I replaced the evap canister vent valve. Problem solved. No more misfires. No rough idle... RPMs are not jumping around. Thanks for your help.

Hi,

You are very welcome and thank you for the update. I'm glad to know you got it fixed.

Take care and feel free to come back any time in the future.

Joe