Xoutpost.com - View Single Post - reset fuel trims; lasted about 60 miles or about an hour

workingonit · #**100** 11-08-2022, 10:04 PM

Quote:

Originally Posted by workingonit

... I noticed that the LTFTs had risen to 9+ (they were at 5-6+ when I drove into the station), which makes me wonder what sort of interaction/influence the testing machine (plugs into the OBD2 port) may have on the X5's sensors or modules, if any? Mind you, my X5 passed perfectly at the same testing station last year, and the fuel trims went wacko in the next couple of days...coincidence??? We'll see.

If the fuel trims don't return to the pretest levels, I'll zero the readings and start over (and might get another MAF sensor to test)....

Two weeks later, and after extensive idling before & after the oil change 5? days ago, I drove the X5 on a 13 mile round-trip to vote. Before the oil change, and after the inspection trip related above, my LTFTs were sometimes at 9+, and my recently reset fuel mpg was at 14.2 mpg. When I completed the extended idling following the oil cange, the LTFTs had hit 10.18 on bank 1, and 9.68 on bank 2, while the mpg showed 13.5 mpg. Extended idling isn't good for this old engine, I guess.

But, after I returned from voting, the LTFTs were both back to 4.5 or so, and the mpg showed 14.2 mpg. I guess you're correct on your assertion, X5chemist

Quote:

Originally Posted by X5chemist

LTFT(s) are affected by long idle times too.

I'm wondering whether other factors had a part in such a quick reduction in fuel trims, like

1) fresh, clean, high-quality oil in the crankcase,
2) a fresh fill-up with Quik Trip Top Tier premium gasoline (the previous fill was over six months prior), and/or
3) a full treatment of STA-BIL 360 Protection Ethanol Treatment & Fuel Stabilizer (1 ounce per 5 gallons, or slightly more)

Whatever the cause, I like the results.

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