Hello-

Please forgive me and point me in the right direction if I didn’t search properly but I couldn’t find a match for this.

We were on the freeway and our LR3 started slowing down while on cruise control. Pressing on the accelerator pedal didn’t produce higher engine speed or a downshift. We pulled off at the next exit and I used the IIDTOOL to check for faults. There were no engine or related faults. After thinking about it, I figured that maybe the Accelerator Position Sensors (APSes) or electronic throttle / Throttle Position Sensor (TPS) could be the culprit so I added all 3 to the live data values to monitor what was going on. Up to about 29% commanded by the accelerator pedal, the APSes and TPS matched within 2%. Above that the TPS stayed at 29-30%. So at 60% on the APSes, the TPS was at 29%. The MIL came on during some parking lot testing so I checked faults and I got bank 1 lean. I also could feel some occasional stumbles or misfires after pulling off the freeway but nothing logged as a fault. After turning the engine off, waiting for a bit and starting again, the TPS stayed within 5% of the APSes at values over 28% and the vehicle was drivable but the occasional stumbles continued.

I thought that the TPS should be close to matching the APSes unless cruise control is on (APSes stay low with no foot on the gas as TPS varies per cruise control) or the ECU is limiting throttle (TPS is lower than APSes due to stability control, traction control, or throttle response changes for terrain management). I am thinking that the stumbling and bank 1 lean fault are happening because the air/fuel ratio are not always what the ECU commanded because the electronic throttle isn't responding as it should.

Does this sound reasonable? If so, is it safe to say that I need a new throttle body to get a new actuator and TPS? I had an induction cleaning done about 6 weeks / 1500 miles ago as preventive maintenance so I don't think that it needs to be cleaned and enough time and mileage went by that I don't think this cleaning caused the problem, either.

Thank you very much for helping me with this.

Here is a screenshot of what my IIDTool is showing...




-Rob