Engine/Transmission (1998.5 - 2002) Pulsating Trottle Peddle

[JMLambert]

My truck has developed an intermitent pulsating in the throttle peddal with a corresponding engine increase/decrease in rpm. This occurs very infrequently along with the loss of the cruise control. I have checked previous posts but have found nothing for the 2nd generation trucks. Any help will be appreciated, thank you in advance. I have 185K on the truck.

 

[rkressg]

Check for codes, you probably have a dying APPS.
Look for P0121 or P0122 (if memory serves me correctly).
The APPS failing is extremely common. If this is the case, there is one that Geno's sells for about $100-$150. It is much less expensive than the dealer (~$450).

They take about 30 min to change.

If you have codes like 1688, 1689, it could be a VP44 going south.

Does you truck have a fuel pressure gauge? If not, it could also be the VP44 starving for fuel.

Ignition on-off-on-off-on (with out starting), they will pop up on the Odometer (at least I seem to think the 99s will do this, this could be a 00 and newer feature).

 

[JMLambert]

There are no check engine light or codes, any further ideas or thoughts on this, thanks in advance?

 

[DACoffman]

99 will not show the codes using the key thing.

 

[cerberusiam]

When you say pulsating do you mean you can feel a vibration, or, is the pedal actually moving up and down? Does this happen at idel, steady cruising, heavy throttle, etc? Are the rpms bouncing up or down in relation to steady throttle?

 

[CAPTPHIL]

Just replaced mine, fourth time in 675k. Rock Auto has one for 249. 00 that is plug and play. Geno`s has apps sensor only for 169. 00. That one requires calibration after install. They both will need you to set the pedal. This is very simple. Turn on ign. switch and VERY SLOWLY press the pedal to the floor then VERY SLOWLY release ONE time. Then you are good to go. The plug and play is a 10min job.
Merry Christmas Capt Phil

 

[JMLambert]

When it starts I have been up to speed 45 to 60 miles per hour in over drive or at about 1600 rpm. I can feel the pedal moving first up and down and the the engine rpm fluctuates up and down several times with the pedal movement. It then may stop or it may continue for several seconds. It will then go back to normal operation. During the times it occurs the cruise control will kick off if it is engaged.

 

[cerberusiam]

Check the CC and TV cables for binding and correct adjustment. Those are th eonly things that will make the pedal go up and down like that. The APPS won't make anything move, it is not caspable of doing that.



Quite possibly a bad TV valve in the trans or more likely the CC is going into some type of cycle.



Will it do it without CC engaged?

 

[CAPTPHIL]

Check your vac. lines. 99 cruise is vac. controlled. If it only does this with the cruise on it is more than likely it is some were in the vac. system. The vac. servo is located under the drivers side batt. tray.

Merry Christmas Capt Phil

 

[JMLambert]

It will occur with the cruise control on or off. It will also do it in either drive or overdrive. I think that it maybe tied to the vacuum sysem as I changed out the heater core and had to remove the dash prior to this showing up. I took the truck to a good transmission shop and they could not duplicate the problem, find any issues with the transmission or find any codes. They suggested that I start (which I Have) replacing all of the grounds and cleaning the contacts on the ECM. I appreciate the responses and any and all help. Thanks in advance.

 

[9412v9824v]

i have a 94 12 valve and i had that happen to me and last time it happened to me about 3 seconds later my tcase blew into pieces all over the highway... ended up replacing tcase and speedo sensor and have never had the issue again... .