arentz07

Topping off fuel is bad, and you should not do it. It probably does not explain why you are having these issues, but it can lead to other issues later on.

https://www.consumerreports.org/cars...k-a1176503026/

Also, you said you use Chevron after an oil change prior. Did you mean after every fill-up?

I am not saying any of these things are causing the issue you're seeing - most likely it's something to do with injectors or, as others have suggested, the fuel pump. But, I also strongly suggest NOT topping off your fuel or running sub-par gas.

Definitely recommend testing the fuel as suggested also.

DLPTony

The stuff is already in there, I say take a long drive, run it out to empty, and fill it up with Chevron…minus additional additives. Their gas has cleaners the others do not. Hopefully the sensor will go off after you’ve made it through enough of the tank. Then stick to Shell/BP 98% of the time and the occasional Chevron for the other 2%. My personal opinion is you should leave the additives and not-so-top tier gas for the jalopies of the world.

Bechtold

I do the top tier gas from QT or Costco. When those are not an option I'll do HEB
I have never had any fuel issues due to fuel. I have had a fuel pump go out on my Supra years ago.

macmaster

OP specifically said “Dealer said that the codes indicate bad fuel” NOT “the fuel sample we took showed bad fuel”

Dont know why you’re arguing me on this.

GoHorns

With regards to "topping off", I meant that I merely fill it up when I refuel. I do not go for the few extra squeezes.

The Chevron fuel system cleaner is added to the gas tank at fill-up every 5,000 miles, i.e., after every oil change.

I doubt there is water in the tank because I burned through over half a tank of gas between last fill up and getting the check engine light. And then burned through another quarter tank between the check engine light and refueling on the way to the dealer. If there was water in the tank, the car would have started experiencing symptoms right away and would have gotten worse. I never experienced any symptoms associated with water in the gas tank.

The dealer is claiming that it is a bad "batch" of fuel causing the problem. As far as I know, the dealer has not tested the fuel. The dealer has not stated the codes are from long-term use of a particular type of fuel. You can get a tainted "batch" of fuel from Shell just as easily as you can from any station. So I fail to see how the choice of gas station caused the bad/tainted fuel if that is the problem.

Based on the codes, I think it is more likely that I have a fuel pump that is starting to fail.

macmaster

I'm inclined to agree with you. Like I said, take your car somewhere else.

Infrared500

Because indications and comfirmations are two different things. I have personally diagnosed fuel issues this way while working at Lexus. Never presented the fuel sample unless asked. What makes you the expert you seem to not know much on the subject of diagnosis as a whole.

arentz07

It would be great, either way, to have some fuel testing done. Though, if it is a bad batch, this may very well be a transient issue.

95bat

Mac is certainly an expert on bad gas 😁

It seems like $700 is excessive to drain the tank. Maybe they're going to remove and empty it, which is a pain. I would want proof for sure that the gas is bad before paying $700, I don't trust the technicians that much.

Infrared500

Codes P0171 and P0174 alone would mean either too much air or not enough fuel. Adding P1170 for the port injector leads one to believe it's fuel and not air related (Vacuum leak). Port injector alone wouldn't lean out the whole engine as its primary purpose is to stop carbon build up on the back of the valves which means the direct injection system is being affected as well. So that leads one to think fuel pump(read pressure) or fuel quality. Next would be to look at live data via scan tool to monitor fuel rail / line pressure and fuel trims. if rail pressure is fine then it is time to take a fuel sample, which takes 5 minutes done at the fuel rail / regulator etc. to confirm contaminated fuel. Very easy to diagnose. Sample is usually taken in a clear container (Plastic) and cannot be kept for long periods as gasoline will eat the container.

MYIS500

Regarding fuel purchased from third party gas service stations. The reason they sell fuel in the first place is to provide a fuel that is slightly cheaper than the franchise brands. To do this they purchase fuel from smaller oil companies or fuel that has a left a refinery that does not meet franchise requirements. The fuel is still good, they are just not going to put their name on it. The refineries sell this fuel directly or through vendors to HEB ,wal mart , Costco what have you to minimize their loss. The fuel is cheaper for a reason. Many times and most all of the time there will be no problem. But these things do happen. It is cheaper for a reason and a reason the franchise brands do not want to put their name on it. This is not my opinion. I live in the largest refinery state, Louisiana. Al the time people tell me to never buy fuel from non franchise brands. You never l ow what you are going to get. To add insult to injury, many franchised stations are independently owned. To make more money they will purchase a portion of their fuel from these third party vendors. It is not to the liking of the brand, but their hands are tied to some degree. Bottomline, their is a reason it is cheaper.
typed on my I phone sorry for the typos

GoHorns

I am in the O&G industry. All the gas comes from the same refineries. Oil companies sell raw crude to refineries. Refineries are not mom and pop operations or small oil companies. They refine the crude and make the gasoline that is sold to distributors. What differentiates Shell from Chevron from HEB are the additives that Shell and Chevron add to the fuel at their respective terminals tat supply their franchisees.

When you buy branded gas, you are paying for advertising and additives. You are not paying for higher quality refining.

flowrider

iTrader: (9)

^^^^That is true, but the additives and detergents are what earn the branded fuel the top tier rating. Those additives and detergents are supposed prevent carbon residue and other performance-robbing deposits from building up on fuel injectors, intake valves, and in combustion chambers.

In regards to the "bad gas". There is nothing that says that fuel can not get contaminated when residing in those underground tanks.

arentz07

I'll just leave this study by AAA here.
https://www.aaa.com/AAA/common/AAR/f...ull-Report.pdf

The point wasn't to do with the supposed quality of the refined fuel, but the additive packages.

DLPTony

Cant read it, I’m promoted to join AAA. (Via my cell at least.)