Friday, February 20, 2009
Throttle Position Sensor
The top two photos are of a Throttle Position Sensor off a 2005 Ford Expedition with 5.4L Engine. The TPS acting up will cause a variety of goofy driving problems, including sticking you on the roadside.
A repair which has cropped up lately in the last couple months on the 5.4 Liter Ford engine is a faulty Throttle Position Sensor. The latest one yesterday was a 2005 Ford Expedition with only 31,000 miles on it. They all had relatively low mileage, between 30,000 and 60,000 miles. The symptoms were relatively the same: no power on the freeway, surging RPM’s, and check engine light on with various throttle position sensor codes. I’m writing this up because when I see something like Throttle Position Sensors acting up on similar applications in a short period of time, it may mean a pattern failure, where I will be seeing more. The pictures above show what a Throttle Position Sensor looks like and where it’s mounted. When the gas pedal is pushed down to accelerate the vehicle, the TPS feeds throttle position electrically to the onboard computer. I included a different view of the plastic intake on the Expedition’s engine.
Tune-ups on these 5.4L Engines can be very expensive. They have a built in problem in that when the spark plugs are removed, they many times strip the threads out of the head. Techs try to avoid this by spraying WD-40 into the spark plug hole at a depth so it pools around the plug base. Loosening the plug a quarter turn at a time and tightening it occasionally while letting it soak in the WD-40 in between helps.
01/12/12 - With so many comments on this post, I decided to add an addendum to it covering some of the further items afflicting the Expedition. Here’s a list of some things I’ve experienced with these.
1. If you have multiple throttle codes, it will almost always mean an electronic throttle body replacement along with the throttle position sensor.
2. The wiring harness running behind the Exhaust Gas Recirculation tube chaffs through the harness wiring and causes a multitude of goofy sensor and code problems.
3. They have updated spark plugs for these. In a related note, misfiring coils and spark plugs also cause an array of unrelated codes. My advice is change both the spark plugs and individual coil on plug assemblies every 60,000 miles.
4. The alternator going out on the Expeditions can and does cause electronic interference, disrupting engine and transmission operation.
5. A link to the Technical Service Bulletin for Transmission and Drivability problems related to a check ball breaking inside the transmission valve body.
6. I came across myriad problems in the East and Midwest after much research where a leaking windshield leaks water into the fuse box. The fuel pump relay is built into it so the fuse box has to be replaced when leakage is found. If the C270 dark green wire at the fuse box has no power it would point to corrosion in the fuse box. That could also cause myriad weird other electrical problems.