New User: Ford Ranger surges between 2100 and 2700 while in cruise.

[Foggy Man]

I have a 2003 Ranger 4 door, 4X4 with a 4.0 engine and a 5 speed automatic transmission. It has 102,000 milles and looks and rides like a new one. However when the cruise control is engaged the engine as indicated by the RPM and sound surges about 600 rpm, no matter what the speed is. Transmission shop told me it was the throttle position sensor. It wasn't. Then they replaced the valve body in the transmission. That was a $400 waste. Does anyone have any expertise on this. Thanks

 

[adsm08]

Well first I'd be going down and asking for my $400 back because anyone who knows anything about cars and still thinks that a valve body can cause or fix your issue isn't even smart enough for McDonald's.

I can think of 3 things off the top of my head, aside from the TPS which was my first though, that could cause this.

1)Bad vehicle speed sensor

2) Bad cable

3) Bad servo


The cable is the easiest to test. Take it off at the servo and pull on it, make sure that it moves smoothly and pulls on the throttle properly.

To test the speed sensor jack up the rear wheels and hook up a volt meter set to AC voltage to the sensor on top of the diff. Start the engine and have someone slowly accelerate, it should produce a steadily increasing signal.

The servo is really hard to test. Best bet to "test" it is to run to the junk yard and hope to pick one up cheap.

 

[Foggy Man]

Thank you ADS08. Just a little more information. It occurs at all speeds from 35 to 70 if the cruise control is on. About every 3 to 5 seconds the engine RPM surges about 600 rpm and then returns. If you lock out the overdrive, everything is fine.