Car will not accelerate when gas pushed

which engine the 3.6? v6?
that shudder is called MISFIRE.
get a tune up yet, even $1.49 spark plugs?
no its not the trans,
if it dont slip, its not trans, (see RPM races? that is slip or too low gear)
if it shifting to the right gears, its not the trans can you count them?
is the CEL lamp glowing or flashing driving, is yes, that means
scan me now. in fact scanning while it shudders, is like (magic)
why start guessing, do a tuneup,
then scan it.
if its is misfire the PCM will tell you what cylinder misfires.

are your spark plugs 6 years old, if yes, why?
going for 200k miles on them.?

cut?
what does it do.
flare or slip
fail to up or down shift correct
shift to wrong gear say 2 to 4, or 2 to 1.?
are you just cruising when this happens
or only accelerating.
or?
did you scan to the PCM for DTC errors yet?
check fluid levels.
is engine overheating,?

Most likely a belt slipping!

isc filthy and sticking open
or TPS bad.
the 2 top fails for out of control idle on 4 liter.
or vacuum leaks

try the throttle position sensor as well, wont run you more than forty bucks give it a shot

Need to have trans rebuilt or find another in junk yard and replace

loosen the gas cap,had same problem,

go to workshop

disconnect exhaust ,muffler or cat may be stopped up

get a 6 cylinder motor drop in this is best gas saver for most vehicles 4 cylinders dont have the ability to push all the weight of a vehicle but runs smoothly
6 cylinders are as i put in words are evenly balanced for everyday use and not gas guzzler either