Xterra Gas Mileage Drop After New Knock Sensor

[b55driver]

Does anyone else who replaced a knock sensor have experience with a change in gas mileage plus or minus?

I have owned my 2001 Xterra 4WD for about 8 years and 80,000 miles. During that time, the knock sensor error code has been set. Gas mileage was in the 17mpg ballpark and range about 300 miles on a tank. The car has 221,000 miles.

Recently, I bit the bullet and replaced the knock sensor. For guidance I used the YouTube video by FlatRateMechanic, which was quite good. I got to do it twice because the first time I had a vacuum leak. The lower intake manifold is a tight fit between the heads and it wasn't fully seated the first time. Some extra wiggling the second time and I had no leaks. I cleared the ECU by mistakenly running the battery down by leaving the key on when I reset the error codes. All the better, the system could learn a new profile with my new knock sensor.

The truck runs better. Smoother, less downshifting, which means to me more power, as you would expect if the system allowed itself to advance the timing.

What I didn't expect was a drop in gas mileage. Now on my third tank and I am getting about 15.5mpg. It is summer and the AC is running. But I have 8 years with this truck and I don't remember the AC taking out that big of a dent.

I was expecting better gas mileage thinking that the engine was now more efficient. Perhaps the ECU sees the benefit of advanced timing and is now feeding in more fuel. I don't know. Interested in other's experiences. TIA

[macgiver]

Was part purchased at Dealer ? a bona-fide OEM , Japanese make (Hitachi , Sanyo , Denso , Mitsubishi , ya get my drift )
Can it be Chinese knockoff ?? Made in China written ( or NOTING WRITTEN ?? ) ..................??

p.s -backtrecking .........what made you want to replace it ? performance ? Time ? OR " someone's " suggestion ??
Anything .............A N Y T H I N G that deep in an engine you go " Top o' the Line " !! On parts now , ya. A wild thought - IF somehow the one you've installed can some how be 'performance-checked' or scoped to see if it JIVES brother ??? For it may NOT be advancing enough , or some similar problem .

[b55driver]

Hitachi.

Reason: trying to have the best maintained Xterra I can. And hoping that there was a good reason why Nissan engineers put a knock sensor in there in the first place.

And, I would get an occasional left catalytic converter bad code in cool weather when lightly loaded (45mph on level roads). The lower cats and all O2 sensors were replaced a year ago due to rust on the cat enclosures. BTW no codes since replacement. But it’s summer. With a known issue (knock sensor) thought that I would fix what I know is broken and go from there.

[macgiver]

Sometimes a "deep-engine" knock sensor will work VERY satisfactorily bolted tightly to ' near-center ' of head (use an existing deep threaded location) . I found that out on '93 J30 , one you tube shows drilling + tap front of bank1 (pass.) - that seemed stupid ................so I removed the Plastic engine cover and found a very CENTRALLY located and DEEP boss exactly in middle of bank2 (drvr's) . 10mm grade 8 bolt going 20mm deep held the new ( DEALER OEM !! ) new knock sensor so well when I plugged it in and performing superbly ON TOP OF ENGINE !!!!!! Mine didn't NEED to be INSIDE w/ huge R&R on intake and such similar ' open heart ' motor surguries .

Point being , some times you may find a VERY easy way to test first , before BIG JOB KILL yOU
And you still scratch head ..............what thf ? is STILL wrong ,ya !