TST and engine knock on deceleration

[daytripper63]

Has anyone noticed that about 1\2 to 1 second after you take foot off go pedal I here a single knock only does it when box is on.

Does anyone else hear this?

 

[BCarmicle]

I hear it if I've had the truck at higher rpms, say 2200 or above, like during interstate driving. My knock will last for more than a second and I usually have the box on 3/3. Doesn't do it unless I let completely off of the accelerator. I don't know what it is either, but would like to know if any has any ideas.



Brandon

 

[lmills]

Mine doesn't do it. Sorry I can't help out

 

[daytripper63]

I hear it if I've had the truck at higher rpms, say 2200 or above, like during interstate driving. My knock will last for more than a second and I usually have the box on 3/3. Doesn't do it unless I let completely off of the accelerator. I don't know what it is either, but would like to know if any has any ideas.



When on Hwy. I set box at 3-3 or 2-2 and on decel I get a single knock but if I set box at 0-0 it doesn't do it, I would really like to at least know what is making sound

 

[one8upcb]

I would just like to add my truck does it also when the box is on. When its off it doesnt do it.

 

[chessie-system]

Mine has done it only on days where the outside temp is above 75. Same thing with full off pedal but it also gives a surge of power with the knock.

Jeff

 

[Pirate4x4]

2 days after mine started doing that, the turbo went boom. Don't know if the knocking noise was the turbo, or if it was a coincidense... .

 

[Fred Swanson]

Does it give the impression the engine skipped a beat? For those with a manual, keep your hand on the shifter when it does it.

 

[one8upcb]

its almost like a backfire just up front in the engine area

 

[SMR1TL]

Originally posted by one8upcb

its almost like a backfire just up front in the engine area

I have noticed a very random missfire (correct term?) or a "pop" three times now. My best explanation of it is would be that one piston did not fire. I had my windows down one time and definately heard it though the exhaust. The settings it happened on were different every time as with the speed and rpm (a mix of 2-3-4 on hp/tq)... only thing consistant was it happened under light throttle, so far never under "heavy" throttle.



Until now I never knew a diesel could "miss-fire". I'd like to know what the deal is.

 

[one8upcb]

What kind of exhaust are you guys running with your trucks that are making these mysterious sounds. I was running the magnaflow and never had these problems. it was when i went straight pipe.

 

[SMR1TL]

I have a 5" setup with the bullet style muffler.

 

[mattymac]

Mark at TST and I talked about this when he was testing his box on the 04. 5's and he said the latest update of the software in the box should do the trick.

 

[daytripper63]

I found out what the knock is

It is a delayed pilot injection after letting of pedal and causes a engine ping

Mark at TST said the reflash will take care of that

 

[one8upcb]

thanks for the info daytripper63. ill have to get mine boxed up and sent out.