Sticking throttle

[TPostema]

Have a 2003 6 sp 3500 dually that the throttle sticks for 1-2 seconds between shiftes. replaced apps sensor and map sensor still sticks. any one run into this before? the throttle cable is not sticking.

 

[rbattelle]

It may be an injection problem. Injector(s) sticking open. Does the truck have any modifications?

Ryan

 

[Little Bill]

I've got an '06 auto that does the same thing since new. If you mat the pedal and release, it will take 1-2 seconds for the throttle to shut down. Only noticable in low gear and neutral in my case. Scared the crap out of me the first time I floored it in a short space. I've heard others mention the same thing and I thought it is an emissions function. I've had chevy gas motors with similar throttle behavior that was emission controlled.

MMeier made this comment a while back -

Are you sure it is actually "sticking", or just hanging high on the RPM's for a few seconds when you let off? The CR engines seem to do this for whatever reason, some say it is bleeding off rail pressure that way.

 

[cerberusiam]

The slight hang in throttle response seems to be an inherent condition with the CR motors. As was explained to me and evidenced by a rail pressure gauge, if you chop the fuel immediately under high demand the rail pressures can spike to well over 26k. This is not only hard on the injectors but tends to pop that expensive rail relief valve.



There is a slight time delay anyway due to fact the fuel delivery to the rail is really a mechanical operation. Even though the ECU can demand the FCA cut fuel to the high pressure immediately, it takes several cycles of the CP-3 to acutally effect the fuel rerouting and reduce delivery to the rail. It seems to be further enhanced by a built in delay to compensate for pressure bleed off. The fuel in the rail has to go somewhere and the return system does not take that much flow.

 

[Little Bill]

Thanks, that's a very clear and sensible explanation.

 

[JHardwick]

It is also exaggerated with a fueling box from my experience.

 

[cerberusiam]

It is also exaggerated with a fueling box from my experience.

Obnoxiously so sometimes, worse when removing TM.



DO NOT whack the throttle hard in a crowded parking lot.





Motor revving, smoke rolling, brakes squealing, tires chirping, and small children and mothers with shopping carts running for cover.

 

[rbattelle]

It is also exaggerated with a fueling box from my experience.

That's why I didn't immediately suggest the typical throttle delay - 2 seconds seems excessive to me.



Mine does it, but more on the order of 1/2 to 1 second.



Ryan

 

[sag2]

Has it always done it or just started? If it just started it very well may be the start of a sticking injector. As noted above the rail pressure does not drop immediately when you let off the throttle. The ECM keeps the pressure high in anticipation that you might want to get back into the throttle. When an injector mechanically sticks, it keeps adding fuel even though the ECM commanded it to stop injecting. That's why you get the sensation that the throttle is stuck.

If that is the case be you really need to have it repaired before you melt a piston.

 

[TPostema]

The only mods are an 4" exh, bulley dog tuner and cold air intake.

 

[TPostema]

Sold the truck. thanks for the help.