1992 Camaro RS 3.1L v6 w/ 5-spd
Symptoms:
1. Really shitty mpg.. like around 10-13mpg... maybe.
2. Pressure build-up in gas tank. (You can hear it when you take of the cap and you can smell the fumes.)
3. Exhaust smells rich.
4. Runs rough when engine is cold (like it is missing) but idles fine.
5. NO check engine light.

Done so far:
1. Plugs and wires were changed.
2. Airbox air temp sensor changed.(First camaro ive seen w/o a maf sensor)
3. Gastank cap changed.
4. Fuel regulator changed. (when I took it off the fuel was shooting out of the rail b/c the tank was pressurized but the car wasnt ran for 2 days)
5. Inline fuel filter changed.
6. All vacuum lines were checked and look good.

Questions:
1. Does the airline off the vapor canister go to a vacuum box or is it just a tube that goes to open air.(different setup in older camaros >.>)
2. Could the purge solenoid or canister be bad?

 

You could have a plugged up vapor canister. You can just pull it out like I did. You just plug the vaccum lines and plug the vent tube for the tank and get a breathable gas cap or get a breather for the line. I don't think that expalins the bad gas mileage though. How is the O2 and injectors?

 

Hello, did you try to replace the vent valve at the tank? Those get clogged or stuck closed. $22 bucks at the dealer, usually not in stock but they will have it for you next day. The vapor canister has two lines other than the tank vent line. One draws fresh air in (line going into fender well) and the other is the output from the purge solenoid which purges the fuel vapor to your intake manifold right in back of the throttle body. Surf ebay for 1992 camaro GM shop repair manual ($74... orange, white, and blue in color) VERY helpful. Also, the crappy gas mileage, get a fuel pressure tester, Actron makes a good one for $25 bucks (Pep Boys, Auto Zone) check the website. Do a fuel pressure check on the car. also get a set of plastic line pinch pliers. This will tell you if you have a leaking fuel injector, a bad pulse damper, so on.

 

My last bad gas mileage V6 problem was the stupid coolant temp sensor.

Definitely mess with the charcoal canister; you need to fix that tank pressure!