i have a thumping noise coming from my truck when i start it and turn it off. it does it as soon as the engine fires up and as soon as the key is turned off. it does like 2 or 3 thumps then its normal on startup. i cant figure this noise out for the life of me but im beginning to wonder if its my motor mounts because i also noticed that it makes the noise the same time that the shifter moves side to side. the trans mount is new with less then 5k on it but im not sure how old the motor mounts are. i noticed this noise after i took my truck into the desert for the first time and it been doing it since.
here is a very dark video i just took of the noise. listen for it as soon as it starts and shuts off. it does it 4 times total in the vid.

 

1 of your exhaust heat shields, maybe. If it was a broken motor mount, I think the knock sound would be louder, and the knocking sound would speed up as you hit the gas. But it could be a loose motor mount. Sorry, not alot of help, I know.

 

I hear the knock like sound you speak of. Can you get somebody to start the truck for you and listen to see where it is coming from?

 

Mine mad e a very similar noise to the one in the video. I now have a very serious rod knock so time for a new 3vze for me. I hope yours is not as serious.

 

Sounds like dieseling to me, but I don't know how that could be with a fuel injected truck. Is it possible for a leaky injector to cause dieseling?

 

i hope not, that engine only has 12k on it.

 

just thinking here, if it was a rod knock wouldnt it make the noise all the time and it would speed up and slow down with the RPM?
just for S&G's how would i check the motor mounts while on the truck? or do i have to just bite the bullet and remove them to check them?

 

I had to listen to the video 3 times to finally hear it

It's possible it could be a bad motor mount...

you mentioned the stick shakes, how much?

if both the trans and motor mounts are in good shape, it shouldn't shake more than maybe 2 or 3 inches from left to right when starting up or shutting off

Dieseling shouldn't cause noises during startup, it just makes the engine stay running after you try to shut it off. My original motor in my old Isuzu was bad about dieseling. I guess the original carb on it was just leaky, and once it warmed up and you shut it off, it would run BACKWARDS, as in TURN OVER IN REVERSE for a full 2 or 3 seconds, spewing smoke out of the carb, untill it finally choked itself out. Don't ask how, but I wish I would have gotten video of it. It never failed, it would do it every time, till I learned to leave it in gear with the clutch pressed in, and just as it died, release the clutch; the truck would even jump back a litte if I didn't hold the brake down, lol. But it would fire right back up every time with no problems and no noises. That is till I bent 2 rods and put a 3rd through the block at almost 7k RPMs