I have a 2006 scion tc. A few weeks ago I bought gas and was driving home and noticed it was starting to drive really jerky. I took it to the dealership and they said it might be bad gas and to run the tank of gas down & put some gas line antifreeze in it to dry up any moisture. I did that and it was still running really jerky and starting to stall out when I would stop. I took it to another mechanic and he said to keep driving it it might take awhile to get all the old bad gas moved through and put some more gas line antifreeze in it. I've done this with 2 tanks of gas now and still have the same problem. I'm getting a code that says misfire of all 4 cylinders but randomly. The mechanic doesn't think it's an engine problem b/c the cylinders are misfiring randomly. Does anyone have any idea how long it might take for the bad gas to get resolved or could it be something else? It's started to have some problems now starting up, not just in the morning, but if it stalls out on me at a stop. I just had the spark plugs replaced. Can anyone help me?

It could take a while. How empty was it when you refiled after the initial filling?

Usually "bad gas" means its been watered down in one way or another effectively lowering the octane.
Ask your mechanic/dealer about adding B+G octane booster.

I suggest B+G because B+G products are what Toyota dealerships use and recommend. They gave me a can and told me to add it and top off with premium after my wife filled my boosted tC with regular.

The tank was empty when I refilled it and I put in 93 octane gas. I can try the B+G product.

B&G have great products. Good call BLUEMEANIE!

I had this happen to me once. Dealership told me I was crazy, but that a whole different story.

Mine just went away. and if your worried about watered down gas, try STP water remover/gas treatment. cheap and works.

Also, try letting your ECU reset if nothing else...

what brand gas were you previously using? and what are you using now?

Toyota recommends to use only top tier gasoline
http://www.toptiergas.com/

^ I've always used Standard/Amoco/BP and now I use Sam's Club. Only time I've ever had something like the OP is describing was when I was NA and I got stopped at a watered down crap shack truck stop in Nowheresville or the time I mentioned above. The detergents don't have much to do with anything other than emissions system performance.

same thing happend to me, it has nothing to do with ur gas...its ur maf sensor its mostly dirty or broken..new one @ autozone will run u about $87 bucks with the old 1...

Well when I worked at the Scion dealership they used Sunoco for their gas. I was told by a few different people, one being a cop, that them and shell buy better gas then say sheets and getgo. Shell being the best gas I guess. So I buy from Shell or Sunoco. When I had my Integra, 94 4 door ls, it ran better(seemed to anyways) with sunoco or shell then sheets, bp, getgo. Exxon I think has ok gas too. But I was told sheetz, bp, and get go were the top 3 to buy the cheapest gas they can get their hands on....which could mean bad gas for people. But idk for sure on this info....but seems to me my tC has been running perfect on Sunoco or shell gas. No problems.

same thing happend to me, it has nothing to do with ur gas...its ur maf sensor its mostly dirty or broken..new one @ autozone will run u about $87 bucks with the old 1...
You can Clean your MAF for like 5 dollars. It works wonders on MPG.