300M Almost stalling

My 300M almost stalls at times when either accelerating slowly after
switching from reverse into drive, or reversing. It stalled twice when I
was reversing fast, but I brushed this off thinking I was being too hard on
the car. The car also shifts hard at times.

What could cause this?

Thanks

 

You don't say what year M - could be important since, for example, there
was a TCM firmware upgrade after the '99 My release that helps with hard
shifting - it helped with hard shifting on my '99 Concorde (same
transmission). Besides having the firmware revision level checked by
the dealer and having it reflashed if needed ($60 to $130 depending on
the dealer), you might need to change the fluid and filter - making damn
sure they use ATF+4 and ATF+4 only - no substitutes (such as "Dexron™
with an additive") that are claimed to be equivalent but are not. Also
you might pull the TCM fuse for a few minutes and let it reset to its
defaults. All three of those things may be necessary. Fluid and filter
should be changed anyway if you haven't already done it. If you plan to
change fluid and filter and get the TCM flashed, do the fluid and filter
first since there is a calibration process involved that is affected by
the fluid properties.

For the almost-stalling, try cleaning the throttle body using throttle
body cleaner per the instructions on the can - many have found this to
correct such situations on the LH cars. Do NOT use carburetor cleaner -
the label *must* say something to the effect that it is good for cars
with fuel injection (it is claimed by some that formulations not
designed for use in fuel injected engines can destroy the fuel injector
o-rings).

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

 

Hi Bill,

It's a 2004 with 70,000KM. I have never changed the trans fluid, I will look
into it. Could the (almost) stalling be caused by this or just the hard
shifting? BTW it has only happened maybe 10 times in 44,000KM.

Thanks,

Steve

 

Sorry Bill I did not see the bottom part of you reply. I did have the fuel
injector/Throttle body cleaning at Mr. Lube.

Steve

 

Normally I'd say that the tranny would not cause an almost stall, but
perhaps erratic torque converter operation could make it seem that way
(i.e., mimick engien stumbling). I don't know enough to speculate on
that - there are probably others here qualified to answer that.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

 

OK. BTW - aren't you still under warranty?

I'd get the tranny fluid and filter changed whether related to the
problem or not.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')