Interesting Code. A little help please.

[NotSoSlowSHO]

Ive been hunting down a weird rich at idle issue lately. During normal driving, the A/F mixture is fine, but at idle (as well as WOT) it is a bit rich. Id like to see 14.5 to 14.8 at idle. But lately, my WB O2 gauge has been registering as rich as 13.2 : 1

Too rich.

Until today, I had never found a fault code. Id check the codes, and nothing.

Today I got a code. Finally.

This one is interesting:

Code 85

"Canister Purge Solenoid circuit failure."

Thats curious, Ive always had a bit of an issue with the vapor purge setup on this SHO. Every time I fuel up I get a good burst of compressed air when I release the gas cap. Its obvously related to the rich at idle issue too. The computer is commanding the solenoid to open to draw fumes from the tank (which in turn draws more air into the intake), but it just isnt happening. So the motor is getting less air than the EEC is commanding. And on our trip to the convention we had a bit of a fuel vapor problem. Every time the SHO's coolant registered hotter than 215, we could smell fuel if the windows were down.

During the trip, I replaced the vapor solenoid that is inline nest to the vapor canister. I dont think it helped zzzzz

SO, how do I trouble shoot this one?

 

[gmorrell]

You don't...

Its quite likely that the driver in EEC which turns on the canister purge solenoid is blown. Bypass the CANP valve. Your carbon canister may also be saturated beyond recovery, be prepared to get a new one, they're not terribly expensive.

I suspect the reason the driver blows is because Ford forgot to put a catch diode on the CANP solenoid valve coil. Whenever the valve turns off, the back EMF overstresses the driver in EEC and eventually blows it up. Ford's TSB fix for this problem was 18 feet of rubber hose to route the fuel vapor canister vent back to the rear bumper, where the fumes hopefully wouldn't bother anyone but the folks behind you.

Read here:SHOTimes fixing fuel vapor smell

Cheers,

Gary M.

 

[Rockledge]

You ought to trace all the EVAP vacuum/vapor lines, as well, make sure the hoses haven't been pinched, torn, or otherwise compromised in some way, and that the hose connections are sound. To do this thoroughly, check the engine bay hoses and then you'll have to drop the fuel tank and inspect the lines back there. You might even plug one end of the EVAP hose(s) with a golf tee and put a vacuum gauge on the other end, the lines should hold .5-1 psi.

You might also want to try a different gas cap, it's supposed to act as a vacuum/pressure relief valve in this system.

 

[NotSoSlowSHO]

Gas cap is new, and has been tested. And it looks like the solenoid that is inline between the charcoal canister and the throttle body NEVER opens. So no vapors are being drawn from the tank.


Ive read that I can bypass the solenoid, but I would have to have a "restricter" in line to limit the amount of vacume draw the intake provides. Any help?

I mean, if I simply bypass the valve, the tank is ALWAYS under vacume.

 

[Rockledge]

The cannister purge solenoid is always hot, it gets a common B+ (red wire) from the CCRM which is also the same B+ feed for the intake butterfly solenoid, fuel injectors, and some other stuff. The PCM controls the solenoid by providing ground which completes the circuit and energizes the solenoid.

Now, you know that up the the common splice point the B+ side of the solenoid circuit is good since your injectors, secondaries, etc. are all working properly. So once you have confirmed that there is actually 12v at the solenoid, then that would leave only the ground side of the circuit as the problem area (meaning there is an open or short in the ground wire, or the PCM driver is bad as Gary suggested).

If the PCM is determined to be the culprit, then why not look for a used one? As opposed to screwing around with the EVAP system...

 

[pjtoledo]

Gas cap is new, and has been tested. And it looks like the solenoid that is inline between the charcoal canister and the throttle body NEVER opens. So no vapors are being drawn from the tank.


Ive read that I can bypass the solenoid, but I would have to have a "restricter" in line to limit the amount of vacume draw the intake provides. Any help?

I mean, if I simply bypass the valve, the tank is ALWAYS under vacume.

You're getting close. There is a restrictor in the tube coming from the tank, it's close to the purge solenoid. That tiny hole can become clogged preventing the engine from sucking the fumes from the tank. That causes a pressurized tank. Clean the restrictor, but do not enlarge the hole, that may create other issues. It's easy to test the purge solenoid, just pull the tube off the canister side and check for vacuum.


Perry

 

[NotSoSlowSHO]

The restricter fitting was indeed plugged

Could that have been my entire problem??