Soon to be new to mack trucks!

[rickykarenpr]

not bad one use truck mack vision is brand new

[stsdavew]

not sure if i should start a new thread or just keep on with this one but I've finally got some miles on my truck and have some questions maybe someone on here could help me out with. The throttle response on the pedal seems rather finicky when shifting, sometimes when i let off to shift and pull it outta gear the rpms drop to idle yet it seems i am still pressing on the pedal. Is this kinda normal for these trucks? I've read on here something about a throttle response upgrade? Another thing i noticed is with the boost pressure, it seems to have some lag when stepping on the pedal to accelerate or when shifting also it cannot make 31ish psi boost (according to gauge) unless the engine is turning faster than 1600rpms. is that normal or should I look into things deeper. I thought maybe it was a bad wastegate diaphragm and changed it but made no difference. truck is making 4-4.5 mpg (uk gallons) and seems somewhat short on power but really have no clue unless i'd get it put on a chassis dyno. would that be something i should do or is there other things i should be checking out first?

[Lavernm]

Your delayed throttle response may be due to the delay built into the jake brake accutation for the cruise control. We have a '99 Ch613 with the 460 and if you have jake on you can feel a real delay in throttle response when shifting. To try it just turn the jake on with the truck parked and accelerate/deccelerate as if you are sifting gears then try it with the jake off and see if it makes a difference.