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Is there such a thing as an automatic transmission modulator valve?

Folks;

I'm having a problem with automatic transmission fluid getting into my cylinders and burning. It happens only occasionally, but in reading about other cars, the advice is to replace the "modulator valve".

None of my three Miata manuals mentions an AT modulator valve and none of the online or catalog parts suppliers has any. I haven't found any discussion of this on this group.

I'll call the dealership on Monday morning, but if anyone knows how fluid can get from the transmission to the tailpipe, please let me know what and where it is.

(It's not engine oil coming through the valve guides, rings or PCV valve. It's not coolant. It's not excess fuel from a stuck injector. Might be aliens, but I'm pretty sure it's ATF coming out the pipe.)

1996 Miata M Edition with 137k miles. No wisecracks about the auto -- only way to get the spouse to swap cars.
Reply to
my_two_cent
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"my_two_cent" wrote

There is a "vacuum diaphragm" on the U.S. driver's side of the transmission just above the pan. The transmission usually doesn't run right when this goes bad.

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Reply to
Ken Lyons

I like the advice to pull off the vacuum line and swab for ATF. I'll do that first.

I've ordered the replacement and will get it on this weekend. Thanks for your response, it is really helpful to get confirmations and it seems like this valve will be really easy to replace. I get nervous when I don't have one of my trusted manuals to guide me.

Reply to
my_two_cent

I pulled off the air line and a fingerful of ATF poured out. Replaced the valve and no smoking and the transmissions shifts more smoothly. Add one more item that can cause tailpipe smoking to the list of symptoms.

Reply to
my_two_cent

"my_two_cent" wrote

Thanks for getting back to us with the results. I'll certainly keep this in mind if our '90 auto ever has the same symptoms.

Reply to
Ken Lyons

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