Throttle Body screw/Adjustment

[1988pathfinderoffroad]

I noticed a little bit of a side effect. Highway mileage is terrible, and I'm thinking it's because I leaned it out so much that the O2 sensor is overcompensating for it. I went somewhere, all highway, that usually takes 1/8th to at most 1/4 tank. I used almost a half.

 

But it does not smell nearly as rich at idle and it doesn't bog down like it used to. So now I know I have a way-too-rich fuel mixture somehow, and I need to fix it instead of doing this...

 

I just used an exhaust gas analyzer. I was thining right the first time when my exhaust got hot. Turning out richens the mixture. I verified this, turning in /clockwise leans it out. I set my screw about 1 to 1 1/2 turns out from fully turned in, which is about correct, It's gonna run rich at idle no matter what, but it runs leaner this way and O2 sensor is much more responsive at higher RPM's. Haven't tried it out yet on interstate, but you might want to crank yours in to where I have mine. You can verify the output of the O2 sensor in mode 2 to fine tune it. I bet your gas mileage will improve.

Edited September 3, 2010 by 1988pathfinderoffroad

[MY1PATH]

The engine uses the oxygen sensor at cruising speed once the idle/switch is off and the engine is at normal operating temperature and the oxygen sensor is warmed up. You can veryify this easily by probing the O2 sensor signal voltage or putting your ECU in diagnostic mode 2, putting your passenger seat forward and having someone ride around with you in the backseat while they watch the LED's You will see them flash once the idle switch is off and they will notice more blinking at cruising speeds, the truck will go into open loop, if the mixture gets too rich

 

 

these are heated o2 sensors BTW. If you test one off the vehicle you can see the heating element glow thru the fins.

[Kyle94]

Yours is MPFI and completely different.

i sawwy... didnt realize that.. whoops.

[Kingman]

these are heated o2 sensors BTW. If you test one off the vehicle you can see the heating element glow thru the fins.

 

Yeah, the heating element is mostly for burning the carbon off the fins. They heat to around 1800F to do it.