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Rough idle after getting gas?


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Its gotta be something in your fuel system. Perhaps has to do with the pressure in the tank after a full tank. Are you topping it off? Gas cap working ok?

 

Maybe there's sediment in the tank?

 

As a precautionary measure (will do some good to have it done anyway), maybe think about having your injectors cleaned, or, if you can swing it, replaced?

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Cap Shouldn't cause stalling. The thing that raises my interest is its only from full to half. That's the only time the evap system comes into effect.

 

What code popped up. If it was a large evap leak gas cap is usually where to start BUT if your having running issues you may have an actual leak in the evap. Which would explain rough idle between half and full tank.

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Wouldn't the cap cause pressure or vacuum if it was failing? Isn't the cap part of the evap system?

 

If the pressure builds up in the tank and the cap doesn't release the air, it could defeat the fuel pump...

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If the cap is bad it would release pressure back in the day the cap is what would release pressure. Before emmissions bs. It has been said a leaking gas cap could aid in premature pump failure but I think that's bs. Fuel cells just have vent tube. The tank just needs to bleed off the pressure between half to full so it doesn't build to much pressure and spring a leak. The evap just puts the pressure and fumes into the intake to be burned instead of releasing into the atmosphere.
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Huh. Well I did get the evap code (p0442) while driving ( after driving for an hour). Time for a new cap I guess. If I could get gas, leave cap off, then start it ok, that would be a good test that the caps malfunctioning eh?
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No. You'll get a large leak code. I'm telling you its in the evap system. Whether you have a bad vsv or a hole in or broken part of a line. A cap would not only effect from full to half. That is when the evap system runs. It needs to be smoke tested. If you want to try a new cap go ahead. It's the easiest. If it works awesome. BUT don't be suprise if it doesn't change anything.
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Ok, I know I'm waaaay late to the party, and I can't quote all the comments I want to reply to so I'll keep it as short and sweet as I can, most likely unsuccessfully. :lol::lol:

 

I work in refineries, so some of the fuel discussion I can comment on, even if I am repeating it. Fuel is refined to the same standards in every refinery (in the U.S.) even if the chemical process is different.

 

Generally speaking:

Crude oil is separated into these basic components:

1. Light ends

2. Diesel

3. Gasoil

4. Naphtha

5. Resid (Coke)

 

It is then sent to a tank farm for storage and "settling." From the tank farm there is a continuous flow to blend tanks, where the finished product(s) formulations are completed. From the finish tanks product goes to a terminal (trucks, tanker ships) or pipelined. Before a product is considered "finished" it is tested. This happens at several different areas within the stream to insure at any given point the product is chemically correct. 87 octane gas is the same no matter what refinery (in the U.S.) it was made in. same goes for 89, 91, 93, diesel etc.

 

Ok, so now that I stated all fuel is refined to the same specifications, here's why it's not all the same:

Every refinery "blends" fuels to get the end product. Every refinery introduces additives to it's fuel for several different reasons not limited to:

1. Meet tech specs

2. Marketing

3. Cut (more fuel=more profit)

4. Keep fuel stable over time

 

So, the answer isn't as simple as "cheap gas." From my point of view that reason describes several different things that could have happened, but basically boils down to this: There is something introduced into the blend post-refinery that is not supposed to be there.

1. Physical particulate contaminants (dirt, rust)

2. Water (leaky underground tank, Ethanol)

3. Separating hydrocarbons due to age or instability

4. Least likely but possible: Cutting fuel with unapproved agent(s)

 

I realize this is not all inclusive of reasons for "bad" or "cheap" gas, I just wanted to share my experience from my point of view. If it was my car, I would just go to a different station. My money is on contaminants, not who made the fuel.

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Lol, for sure :lol::lol:... I was more addressing the "cheap gas" comments, and my experience in refining. I thought a new perspective in how fuel is made might give new insight to people regarding that.
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Replace the cap. If not get a smoke test. You can be chasing this forever. Could be the FP or the fp gasket too.

 

Are there smaller lines underneath the car at the gas tank that go to a breather element of some kind? I can't remember. Check those too if they're there.

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Sheets and wawa are grade b gas. I won't put that in my lawn mower.

 

And any station that doesn't sell 93 is a red flag to keep going.

 

I agree.. but wawas around me only have 92 octane and I don't run any less than 93 so I dont get gas at wawa ever

03 WRB WRX (RIP)

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When I had my 93 tune I didn't use anything other than Sunoco 93. Now that I'm paying for gas at hundred miles a day convenience and price or important. After the 22nd when I change jobs I wont be commuting. So I'll be back to the premium 'a' gas.
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So I got 15.4 gallons of gas left the gas cap off and started and I had the same results rough idle a stall tough restart rough idle but as soon as I drove away it was fine

 

 

Sent from my iPhone using Tapatalk

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