What Is Considered "running Rich"

DuderMcMerican said:

I suspect my car is running rich. It's not getting great mpg, and there's always been a faint fuel odor when I stomp it. Also, I feel it's not getting the acceleration it should.
IS running rich? Is the fuel odor a dead giveaway? Is there a certain MPG threahold that indicates it's rich?

Everything is stock--no deletes--in case that matters.

Thanks

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A rich condition will set a code in the 4x/9x series of codes (41,42,43,91,92,93).

The gasoline smell could be due to cracks or damage to the gas tank vent system lines or carbon canister.

Code 85 CANP solenoid - The Carbon Canister solenoid is inoperative or missing.

Revised 11 –Jan_2015 to add warning about vacuum leaks due to deteriorated hose or missing caps on vacuum lines when the solenoid is removed.

Check vacuum lines for leaks and cracks. Check electrical wiring for loose connections, damaged wiring and insulation. Check solenoid valve operation by grounding the gray/yellow wire to the solenoid and blowing through it.
The computer provides the ground for the solenoid. The red wire to the solenoid is always energized any time the ignition switch is in the run position.

If you disconnected the carbon canister and failed to properly cap the vacuum line coming from under the upper intake manifold, you will have problems. You will also have problems if the remaining hose coming from under the upper intake manifold or caps for the vacuum line are sucking air.

Charcoal canister plumbing - one 3/8" tube from the bottom of the upper manifold to the rubber hose. Rubber hose connects to one side of the canister solenoid valve. Other side of the solenoid valve connects to one side of the canister. The other side of the canister connects to a rubber hose that connects to a line that goes all the way back to the gas tank. There is an electrical connector coming from the passenger side injector harness near #1 injector that plugs into the canister solenoid valve. It's purpose is to vent the gas tank. The solenoid valve opens at cruse to provide some extra fuel. The canister is normally mounted on the passenger side frame rail near the smog pump pulley.

Connecting the gas tank vent line directly to the intake manifold will result in fuel vapor being constantly sucked into the intake manifold. There is unmetered fuel that the computer cannot adjust for. The result is poor idle and poor fuel economy.



It does not weigh but a pound or so and helps richen up the cruse mixture. It draws no HP & keeps the car from smelling like gasoline in a closed garage. So with all these good things and no bad ones, why not hook it up & use it?


The purge valve solenoid connector is a dangling wire that is near the ECT sensor and oil filler on the passenger side rocker cover. The actual solenoid valve is down next to the carbon canister. There is about 12"-16" of wire that runs parallel to the canister vent hose that comes off the bottom side of the upper intake manifold. That hose connects one port of the solenoid valve; the other port connects to the carbon canister.

The purge valve solenoid should be available at your local auto parts store.

Purge valve solenoid:



The carbon canister is normally mounted on the passenger side frame rail near the smog pump pulley.
Carbon Canister:

@jrichker
Appreciate the canister info. '94 GT 5.0 I bought recently (~ 3 months) gets poor mileage, otherwise runs perfectly well. It's my 4th. 5.0HO, so I'm accustomed to "good" or "bad" running. Car has had smog pump bypassed, shorter belt I suppose, hose connections to the check valves gone.

More importantly, the canister is gone, as are both the solenoid valves associated with it. I have not been "into it" enough yet to determine what the disposition of the vapor line was, but will soon.

Today I checked for stored codes, found none! Also, CEL proves out on start-up, turns off, stays off. How is it not throwing code(s), any ideas appreciated. imp