BismoFunyuns

I have a 2006 GT with ***** thumpr cams. It's an automatic, with 4.10 gears. My question is, when the car goes from drive/neutral to drive or reverse, once the motor is completely warmed up, it will lose it's lope sound? Like the lope sound will come and go, but it mostly sounds kind of weird. Almost like how a diesel truck sounds when idling. Then the lope will come back, and it just goes back and forth between those sounds.

I've always marked it up to these newer motors just don't work the best with cams. I've been in my friends LS1 car with cams and it would constantly have that lope sound to it.

Any ideas?

BismoFunyuns

i've added a video so you can see what i'm talking about.. notice how it starts idling strage about 18 seconds into the video after i put it into drive? then it gets the lope back once i put it into neutral?

i've always found this odd.. as the car runs fine and i dont have any engine lights. is this something with all cams on these cars or just the thumprs in general?

BismoFunyuns

a/c and air is all turned off as you can see. once i put it back into drive the second time, it started loping nicely and then starts that weird idle again. it just goes back and forth between it for some reason. but it constantly idles fine/lopey when in drive and neutral

Dino Dino Bambino

The idle speed seems to increase slightly when you put the shifter into D, and that tends to reduce the lope. Probably normal. You can adjust the N and D idle speeds with the tuner.

BismoFunyuns

doesn't it seem odd though that it does still lope in drive then changes to that odd sounding idle?

BismoFunyuns

the idle speed in drive is lower than neutral/park. It's currently set to 750. I can't get that noise to go away until I set the speed down to like 500-550. Which is too low because the car acts like its going to die when coming to a stop

08'MustangDude

A lot of that has to do with valve overlap with the bigger cam. That is not going to go away
without timing tweaks. It sounds like it's lop sided when it does that..

It could also be that one bank is slightly out of time or a cam phaser is slightly off on one bank.

Changing the idle speed up also speeds up the cam movement, so is passes over the lop-sidedness
quicker and then seems to even out. It just has that not so sweet spot at a certain RPM...

BismoFunyuns

So do you think its just the cam in general or a timing/tune issue? Would you think that something out of time would cause an engine light?

BismoFunyuns

And you say about the increasing the idle speed, that it has that not so sweet spot.. It seems like anything over 500-550rpm idle speed will cause this issue when the car is in drive. This is literally only an issue when in drive.. if its in neutral/park it doesnt make that sound. No matter the idle speed

Dino Dino Bambino

The torque converter is spinning when the selector is in D, and the increased engine load could be the reason for the change in sound.