$EE CCP disable/delete

[fbody_Brian]

it is really strange. I disabled the error code, then I took it all off. When i cranked it up after that it was way lean at idle. I searched all over for something that I may have disturbed, but found nothing, so I hooked it back up and the afr went back to normal. I then realized that I had previously had problems with a very rich idle and leaned it out, so I corrected that part of the tune back to stock. Idle went back to where it should have been, but way lean everywhere else cruising. I noticed that the solenoid may have been stuck, because there's always vacuum going through it. I hooked the vent line straight to manifold vacuum and it ran richer. It seems like it should have the opposite effect. Anyway, I just disabled it and adjusted the tune some to compensate and the afr looks good now. It just really caught me off guard, wasn't expecting it at all.

[1project2many]

Constant purge will cause rich mixtures. It's important to investigate potential causes of problems before trying to tune around them.

[fbody_Brian]

Constant purge will cause rich mixtures. It's important to investigate potential causes of problems before trying to tune around them.

What causes it to create a rich condition?
It seems like it should cause a lean condition because it is unmetered air entering the intake. Just trying to understand. I would never have thought that a stuck open evap solenoid would create a rich condition.

Everything I've read says the opposite, that a stuck open evap solenoid causes a lean condition.

[1project2many]

There are two valves: Vent and Purge. If the valves are stuck so vacuum is constantly applied to the tank then the engine will be picking up fuel vapor. If a vacuum is created in the tank then the combination of warm fuel returning from the engine and low pressure in the tank will cause the fuel to create excessive vapors. Even if both valves are not stuck, a stuck closed vent valve can cause the engine to draw excess vapors. In your case it sounds like both valves may be bad. Follow the link below for a basic explanation of how the purge system functions.


(Original image at http://chevroletforum.com/forum/taho...olenoid-46364/)

[fbody_Brian]

Very informative.
Thank you