Cap and rotor???? Don't tell me, let me guess.... 3.0 litre Mitsubishi
Engine perhaps????

And, wait for it, the A604 4-speed automatic transmission?

At somewhere between 40 to 50 is a transmission shift point. On my old
acclaim, and on my cararvan - both of simialr vintage to yours, my
transmissions do NOT like it if I try to maintain a steady speed of
just above 60 kmh (oabout 40 MPH). I sold the Acclaim so I cannot
comment further on it, but the Grand Caravan's transmisison handles
this situation a whole lot better since it was rebuilt that it did
before! Try pulling from "OD" to "3" and see if the problem is
minimized. Also, if you have the button, press "O/D OFF" and see if
that helps.

If your transmission in that Acclaim has not been rebuilt yet, then it
is likely overdue. Another thing to check is the transmission
computer. If there are little fins on the side, then you have a
computer which is "flash" upgradeable. If this is the case, go to a
dealer and have them upgrade the trans computer with the latest
firmware.

Go to a good trans shop and have the transmission computer data read.
The data in the computer can tell you if the tranny is starting to
have problems. A GOOD trans shop will read the codes for free.

But that 3.0 litre mitsubishi is a piece of crap. I eventually sold my
acclaim because of it. Mine used to run rough - sometimes, and it
literllay PUKED oil from every engine seal. Fill up the oil and check
the gas was my motto.

The only thing I managed to do that ever helped that engine was to
remove and touroughly clean the throttle body. It is realtively simple
to remove. Once it is off, set it on a stack of old newspapers and
then remove ALL the little bells and whistles on it. You will need a
Torx driver to do this (or at least you did on mine). Go at it with a
can of Throttle Body Cleaner (NOT Carb cleaner). Make sure you clean
ALL the passageways and orofices.

When I took one of the little things off mine, there was a spring, and
a conical brass part which were completely choked with thick black
crud - so much so the parts would not even move.

Took me a couple of hours to clean it properly and reinstall. The
motor ran a WHOLE LOT BETTER after that.

You also might want to check your engine codes as well. Google the FAQ
on this newsgroup for code information. Note: You CAN read the engine
codes yourself - you CAN NOT read the Transmission codes without the
proper tool.

And when was the last time you replaced your O2 sensor???

Just some thoughts.