Alec5y6

Okay so i bought this 92 es 300 a while back. its got 185k on it and it starts up and runs good as should. but as i am driving it. maybe every 100 miles or so it will start idling rough and has almost no power. and if i park it and disconnect the battery to reset the computer it goes away for like 10 minutes and comes back. it also is building up pressure in the fuel tank and i unscrew the cap and it releases the pressure. sometimes it fixes it and sometimes it doesnt. it doesnt overheat or do anything goofy like that. does anyone know what it could be?

StuckInVA

I'd like to start my reply with an explanation.
Every gas tank needs to be vented in some form or fashion. Pressure can build due to the expansion of fuel or vacuum can be created due to the consumption of fuel, and either condition can cause leaks in your gas tank. In the old days everyone used a vented gas cap; It was simple and it worked. Unfortunately gasoline vapors pollute our atmosphere with hydrocarbons.
Introducing the charcoal canister! By venting the fuel vapors into a container filled with activated charcoal the hydrocarbons can be stored until they can be successfully consumed by the engine. it also vents back to the tank allowing fresh air to fill any space in the tank preventing the formation of a vacuum.

This is the only vent for your '92s tank and a replacement is not cheap. located on the drivers side of the engine compartment it has 4 ports running from the tank, wheel well, underneath the engine, and to the TVV near your engine temp. sensor.

I recently fixed mine, and it's much cheaper than purchasing a new one; if you're interested I'll go into further detail. You always have the option of the Ebay part, I sourced one for ~$60

Another option is to disconnect the hose coming from the tank. this is theoretically dangerous, should lower your fuel economy, cause you to fail emissions testing, and might not fix anything other than your venting issue. I ran for about a week like this.

StuckInVA

Also, welcome to the Club.