In article
outautos.com>,
"2forgetmenot" > wrote:

> Let me state my problem again with this.
> Everyday I warm my car up for 5-15 minutes before driving. After
> approximately 2-5 minutes of driving the thermostat needle starts to
> slowly drop down to cold, the car down shifts by itself and the engine
> roars loudly becaue the RPM's are so high when the transmission down
> shifts. I took my 94 Mazda Miata to a Mazda dealer. They first said the
> thermostat was getting stuck. They checked that and that was not the
> problem. Then they did some type of engine cleaning (so they said)which
> cost me $74. The final analysis was I probably had a bent valve, which
> would have cost me $750 to repair. I elected not to repair, becaue this
> was an educated guess, but I wasn't interested in taking a stab in the
> dark for $750. Any ideas?
>

Automatic transmission with an in-radiator cooler, presumably...

Temp drop MIGHT have to do with the cold tranny-juice hitting the
(already hot) radiator once you've put it in gear and the fluid starts
circulating.

Downshifts... Possibly the cold tranny fluid picking up heat from the
radiator changes behavior - perhaps gets "thinner" suddenly - and alters
the pressure it's putting on things enough to cause the downshift? High
RPMs in the lower gear are to be expected, so the key is figuring out
why the tranny is downshifting, I'd say. I'd strongly suspect that the
temperature difference between the warmed-up engine and the cold tranny
"mixing juices" in the radiator is responsible for the temp change, but
I'm trying (and failing) to come up with some way that warming the
tranny fluid could cause a downshift.

What happens if you continue driving it? Does it "come back to normal"
over the course of - oh, say 10-15 minutes (as the tranny comes up to
full temperature)? or does the misbehavior continue indefinitely?

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