V4 to V8 engine firing

[truckingfun]

Hey everyone,

 

I was wondering if anyone else has had issues with their engine not engaging V8 mode correctly.

 

When I coast the engine drops down to V4 mode no problem but when I re-accelorate either lightly or hard the engine seems to miss fire when it kicks into V8. Its gotten to the point the whole truck 'shudders' and you can hear a decent bang. This only happens when I go from coasting, never an issue from a dead stop.

 

The dealer can't seem to find anything wrong and says that's normal... Thoughts?

 

5.3L V8 with the 3.08 (yeah my mistake on that!) SLT crew Cab

[darkfox1]

Not normal at all.

 

I can't even feel my truck go from v4 to v8 and visa versa. The only way I can tell is if I'm watching the mpg with the v4/8 icon.

 

Sounds to me like some kind of lifter problem? I've never held any of the DOD stuff in my hands but as I undertand it it allows the lifters to collapse so that the valves stay open and the pistons are just along for the ride. Sounds like maybe one of your valves isn't er.. inflating.. at the right time?

 

Take the dealer service guy for a ride if you can make it happen. They probably can't make it happen on their test drives cos they dont drive it like you do.

[truckingfun]

Thanks! I'll try suggesting I go along for the ride.

 

Would the lifter make a knocking sound? From day one my wife and I have both said the truck is loud at idle (Compared to my 2011) with a knocking sound bit assumed it was just the new engine.

[darkfox1]

Sounds like a loud sewing machine yea?

 

That's direct injection. Nothing to worry about there.

 

I'd suggest you drive and he rides. That way you can make sure you replicate it. I had a bad plug wire on my first (and last) ford and it took 3 tries before they finally let me drive and I proved the problem within 3 minutes of driving. They flog people's cars on test drives it seems.. so they may not ever even get into v4.

[Silverado-Hareek]

Are you sure the "bang" you are hearing is coming from the engine and not the transmission? There's numerous complaints on this forum about a lag in the transmission dropping into a lower gear when you give the truck gas to accelerate and it causes a hard shift with a bang.

[milligan]

I agree with the transmission. If you are going from coasting to accelerating hard, then the slack in the driveline will cause a bit of a noise and possibly feel rough depending on the conditions.

[sharper]

I'm with these guys - I never even notice it switches between 4 & 8 cylinders unless I'm on one of the screens that shows it.

[darkfox1]

The transmission clunk is certainly noticeable, but its more of a feeling. I call it "falling off a cliff." It feels like the transmission really damages itself, but.. all of my 6 speed auto GMs have done this, so I don't think its unusual.