I picked up a new rig last week and one thing I've noticed has me confused. When I'm getting off a highway or coming up to a light and depress the clutch as I coast to a stop the RPMs fluctuate a few hundred almost revving up and down a few times. Is this a normal thing with the 6-speed trucks? I really don't think the truck has a fuel issue w/ only 30k on it, it's got a fresh filter and doesn't hesitate or lack any power when in the fuel. Let me know what you 6-speed guys think?

Thanks, Eric

 

Mine doesn't do that, 'tho sometimes it will hang @ 1000 rpm and you have to let the clutch out with it in gear to bring it down, then its fine...

 

Only time mine will sort of do it is if I was lugging it down some at the moment I pushed in the clutch. I have only seen it happen a few times.

 

Mine does that all the time. I've never found a reason and it hasn't changed in the last 10,000 miles since I've owned it so I just don't worry about it any more.

 

I've got pretty darn good working knowledge of these CR trucks and I am not sure why it would do it. I can be sitting still and rev all I want and when it settles down there is no bounce, but coming off a load or speed it bounces.

 

i think is because of the rail pressure when you let out of the throttle its going to spike. just my stab at it.

 

Mine would bounce slightly and would hang at around 1000 RPM sometimes when I pushed the clutch in and coasted up to a light. I could drag the clutch slightly and it would drop down to 750 and stay there. When I changed out the injectors, the problem went away.

 

If you are coasting in neutral or clutch in the ecm will hold the rpm's above idle (usually around 900 - 950). Next time you are somewhere you can experiment safely, get rolling put the truck in neutral and coast, observe the rpm's, now step lightly on the brakes. You will see it go back to idle. If you let off the brakes and keep coasting the rpm's will come up a little again. It is definitely on purpose, what purpose I don't know, but on purpose for sure. My guess is the rpm's raise to either keep power steering and brake pressure up or to keep the trans input shaft turning to keep oil splashing around.

 

I'll have to do that, although I think mine is still doing it with brakes applied.

 

My '05 just started doing this at 125K miles. Also bogs just ever so slightly on take off and produces more black smoke that I'm used to seeing at take off. I can also feel/hear slight surging when moving down the road...anyone got any ideas what is causing this ?

Regards
Gemstone