2001 Dodge Dakota SLT 4.7L V8

Recent work on vehicle:
Replaced Upper Radiator hose(2 weeks ago)
Replaced Rack and Pinion(3 weeks ago)
replaced Throttle control Valve and Throttle Position Sensor(4-6 Months ago)
replaced crankshaft position sensor(8-10 months ago)

Behavior: im not sure what to call it when it does this, but when hitting the gas from a full stop the truck seems to loose power then regain it, causing the truck to lurch forward over and over a few times till it finally shifts to a higher gear, the RPMS also go a ways too high before making that first shift.

unsure if its a related issue or not, My cruise control stopped working entirely the same time i started having these issues, i can turn it on and off, it just wont set at any speed.

went to autozone and had the codes read as the CEL was on, and these are the codes and probable causes that they printed out for me.

1. p0123 Throttle Position Sensor
Probable causes.
sensor open or shorted Internally-replace component.
Check connector and wiring to sensor.

2. p0121 Throttle Position Sensor
Probable Causes. (Same as First)

3. p1294 Idle Speed Not Reached
Probable Causes.
Mechanical Condition- Vacuum Leak
Throttle Cable not free
Idle speed screw mis-adjusted

i replaced that sensor before, but ive never had the vehicle act this way, im suspicious of a vacuum leak but ive never had one so i dont know what happens when you have one.

Thanks for any help and thank you for your time!
Chris

 

A couple of things.

1. You can check codes yourself, you don't need to see Autozone. With the truck OFF, turn the key to RUN (don't start it), then OFF, back to RUN, then OFF, and finally leave it in RUN. Codes will display in the odometer window.

2. P0121 is accelerator position sensor (throttle position sensor) signal voltage too low and P0123 is throttle position sensor voltage high. Replace the sensor but don't get it from AZ. Get one from a dealer. Lately lots of people are having trouble with aftermarket sensors.

3. The cruise control servo does run on vacuum. Check all the vacuum lines running from the servo all the way back to near the power booster.

4. A vacuum leak will make you idle high. You can rent/borrow a vacuum gauge from most auto parts stores.

5. The cruise control cable might be hanging up. You can disconnect it at the throttle body to test.

6. NEVER adjust the idle speed screw. The RPM is controlled by the PCM and the IAC.

 

Thanks for the speedy reply! all this advise is much appreciated.

ill come back after and let you know how things go.

 

alright so i went looking in my console and found the old Throttle position sensor in the box for the newer one i bought, With...the recipt! it has a limited lifetime warrenty so i took it back to advanced with the recipt and got a new one.

as i was taking the sensor off my truck i noticed it didnt have that little cardboard gasket that goes between itself and the throttle body, im thinking this could be the source of my vacuum leak.

so i put the new one on, Gasket and all, and reset the codes on the computer (is there a trick to this? i had to disconnect the battery) and went on down the road! its driving great now, and the cruise control works again!

Thanks for your advise again 00DakDan, that little trick for reading the codes with the key is really cool and the old know it all at Advanced Auto didnt even know about that one lol

 

Great! Glad it's working.