My wifes 2000 5.9L Automatic 4x4 started yo yo-ing RPMS when cruising at highway speeds. At first I thought she was crazy, but I took it to work the other day and sure enough it started going up down up down up down. When it does this it normally goes up about 250 RPMs then back down to normal. It will do this continuously until you change your speed. Any Ideas????

 

Throttle Position Sensor

 

Sounds right. Mine sometimes yo-yo's while idling after starting it up.

 

That's what I thought at first but the TPS is $110 and I really don't want to throw parts at it. Most of the time when a TPS goes out, it has a dead spot in it that acts up every time the sensor hits the dead spot. This does not act up all the time. I actually had to drive it about 45 minutes to get it to act up. That's why I am thinking it may be something else.

 

You might want to look around a little more on the TPS. It's like a $30 part and my money is on it being the problem.

 

RockAuto.com has them for 32.76, I'm sure a local store might have it the same if not cheaper.

 

I thought that was a little high. I just replaced the TPS in my RAM with a 5.2l in it and it was $41. But, I called the 4 places inmy town and they all were right at $110. One place has them for $96 but they aare out of stock at the moment. I'll check around on the internet. Thanks for the info.

 

I had a similar problem awhile back on a different vehicle but the fluctuation would stop if I turned of the OD. Turns out the tranny was shifting in and out of OD because the tires weren't the correct size (too tall) and it confused the ECM. Go figure

 

It's your TPS and Mean Green is right as far as price goes, I replaced mine and it was close to $40. Really easy to replace also just two Torx screwsthat hold it in. Mine was doing the same as your's all the time highway, city, idling - replaced the TPS and no problems since,

 

Thanks for all your help. I found the TPS on RockAuto and will order it on the 30th when I get paid. Thanks for turning me onto that site, they seem to have some good prices.