Lean Codes with Unusual Fix

[BumpyZ4]

One day on my 2003 E85 I noticed that my average MPG was down 3-4 MPG, car was running fine, and then the next day I got the "service engine soon" light. Read the codes and it was showing P0171 & P0174 both banks lean. I also looked at the live data and the long term fuel trims were both around +28%. I looked for vacuum leaks at all the usual places and found none. I smoked checked it twice and only found a small leak at the DISA valve, fixed but no change. Fuel pressure was good, sprayed brake cleaner everywhere I could reach with no changes. I then removed the intake manifold and found that the main vacuum hose from the manifold to the suction jet valve was hard as a rock and leaking. While I had the manifold off I refreshed the CCV and the cooling system while I had access and since everything was original. Put it all back together and went for a test drive but the long term fuel trims only decreased to +21% so better but still waaay bad.

I then remembered that all of my problems started after I filled up my gas tank. So with half of tank left I went and filled it up from another gas station and took it for a ride. The long term fuel trims went from +21% to +14%! I now knew that I was on to something. I drove the car until I had less than a quarter of a tank and filled it up again and took it for another ride. 30 miles later the long term fuel trims were now +5% and getting better!!!

The only thing I can think of is it was just bad or mislabeled gas. I would have never thought that gas would have caused a "lean" condition!!

 

[sw4nny]

Where from and what octane were the respect,good and bad fuels from?

 

[Zulu4]

Interesting. Thanks for sharing

 

[enuff_zed]

Very interesting.
Son-in-law borrowed the freeleeta for a run to Sheffield.
After refuelling he got the engine light on.
On the way home he refuelled somewhere different and the light went out again.
Scanned it and got 3 or 4 codes all relating to lean mixture.
Checked every pipe, especially the new inlet pipe I'd just fitted in case I'd cocked up. Everything was good.
I've reset the codes so we'll see what happens.
Would be a result for me if it was just dodgy fuel. Fingers crossed.

 

[Smartbear]

Very interesting.
Son-in-law borrowed the freeleeta for a run to Sheffield.
After refuelling he got the engine light on.
On the way home he refuelled somewhere different and the light went out again.
Scanned it and got 3 or 4 codes all relating to lean mixture.
Checked every pipe, especially the new inlet pipe I'd just fitted in case I'd cocked up. Everything was good.
I've reset the codes so we'll see what happens.
Would be a result for me if it was just dodgy fuel. Fingers crossed.

I’ve read that e10 fuel can cause lean running, hence poorer economy as the car has to richen the mixture to compensate for it. Not heard of it causing fault codes though? :?
Rob

 

[BumpyZ4]

Where from and what octane were the respect,good and bad fuels from?

I'm in the States but the good gas was Shell 93 octane.

 

[enuff_zed]

Very interesting.
Son-in-law borrowed the freeleeta for a run to Sheffield.
After refuelling he got the engine light on.
On the way home he refuelled somewhere different and the light went out again.
Scanned it and got 3 or 4 codes all relating to lean mixture.
Checked every pipe, especially the new inlet pipe I'd just fitted in case I'd cocked up. Everything was good.
I've reset the codes so we'll see what happens.
Would be a result for me if it was just dodgy fuel. Fingers crossed.

I’ve read that e10 fuel can cause lean running, hence poorer economy as the car has to richen the mixture to compensate for it. Not heard of it causing fault codes though? :?
Rob

Me neither tbh, but I'm either missing something or grasping at the straw that's been offered.
The car has sat for ages and he borrowed it before I'd really had a chance to shake it down, but I had previously checked and cleared all codes, so I know they were new.