Fresh Rebuild w/Quadzilla Dead Pedal, High Idle Problems

[AZHobo]

Howdy,

 

I've been researching dead pedal issues, but I haven't seen any similar to mine.  I have an '02 3500 6speed with 10k on an extensive and expensive rebuild.

 

In the last 4,000 miles or so I've been having problems with high idle after extended running and three dead pedal instances.

 

After running the truck at highway speeds for 30 minutes or so the truck idles over 900 rpm, the longer the running at highway speeds, the higher the idle.  After running for several hours it's idling at 1,150 rpm.  If I shut the truck off and restart (after fueling, for example) the idle returns to normal.

 

I've had three dead throttle pedal experiences after extended running.  While driving the engine will cut to idle with no throttle response.  All three times it returned to normal after shutting it down for 30 seconds then restarting.  All three events were isolated - they didn't happen again during that trip.

 

The engine has stout internals with a 62mm turbo, 100hp DDP injectors, Fass 150 and a Quadzilla programmer.  The VP44 is original with 174k. 

 

I'm not a saavy mechanic, my skills are limited to oil changes.  I haven't been watching full pressures, I will start keeping an eye on that.  I also haven't checked for any codes as I don't have a reader handy.

 

Quadzilla issue? or could this be a problem with the VP44?

 

Any help is appreciated.

 

Matt in New Mexico

[dripley]

Fuel pressure and codes are going help more than you know. I have had dead pedal from fuel pressure and wiring issues. Do still have the original lift pump on it too?

[Mopar1973Man]

Clue... Dead pedal comes from two places. Either bad APPS sensor which typically with pop a P0121, P0122 or P0123 code instantly. The only other device that can create a dead pedal is VP44 which may or may not trip any codes at all. 

 

We need to see your fuel pressure and error codes. A lot of error codes do not set the check engine light. 

 

Suggestion is turn the Quadzilla to ZERO and see if it repeats. I really don't think the Quadzilla is responsible, personally.

[Me78569]

Agreed.  Code scanner would likely give you your answer.

[Mopar1973Man]

I've got a hunch its the APPS sensor. Typically people fall for the adjusting the APPS voltage line which is totally wrong. Then over adjust the voltage and get the APPS stuck in throttling mode and now the APPS never reaches idle position and can run the ECM idle software. This would cause high idling issues. Then if the APPS is damaged and going out of range too much then the ECM drop the throttle to ZERO and disregards the APPS sensor for a period of time because either too low of voltage or too high which can be seen as WOT on steroids. So to keep the driver safe the ECM just drops the fuel to zero and doesn't listen to the APPS sensor. 

 

Quadzilla wise it listens to the CANBus and basically hijacks the data and reassigns fuel and timing commands and sets the priority bit to override the ECM. Quadzilla has zero control of idle functions only the ECM does. Once the RPM falls below I think about 1,000 to 1,200 range the Quadzilla gives up control and hands back to ECM. Now as for the cutting out completely you should be able to set TPS and Engine load up on the Quadzilla display and monitor both. When it does cutout see if the TPS drops. With the ignition on and engine off you should be able to work the throttle slowly up and watch for sudden drop outs or spikes. This would show a bad APPs sensor.