TPS value at idle 17.8%

[thetoulman]

Hello,
99XJ 4.0 AW4
According to my scan tool, the computer is seeing a tps value of 17.8% at idle. (88% at WOT) Is this normal? Is there a specification of typical values available?

I am hunting down reasons for poor MPG (14 Highway) and this tps value seems a bit high to me.

Thanks in advance.

[4.3LXJ]

I can't tell you about the TPS value, but the number one culprit for bad milage is a worn out O2 sensor. If it hasn't been changed in forever it will be worth your while to change it. It should be done when you tune up the engine. Just because it doesn't throw a code doesn't mean it isn't worn out. The code only comes on when the wires are broken or the heater in them doesn't work

[thetoulman]

Thanks, O2 sensors are cheap enough to throw one in. Still curious about the nominal values for the TPS though.

[Cheromaniac]

According to my scan tool, the computer is seeing a tps value of 17.8% at idle. (88% at WOT) Is this normal?

Yes they're normal.
Poor gas mileage, especially during highway cruising when the engine's ECU is in closed loop mode, is most likely due to a malfunctioning upstream O2 sensor. As 4.3LXJ said, you may not necessarily get a code.