My 2003 Chevy Malibu takes spells where is does not shift into 3rd or drive. We took it to a transmission shop and they could not find anything wrong with it. Several mechanics drove it for a couple of days and could not get the car to act up. They put it on the computer and nothing showed up. They mentioned they had tried to read a memory chip or something and that didn't show anything either. The car will go for days without doing this. They said they could not diagnos the problem if it didn't do anything when they drove it. We picked the car up yesterday from the shop and drove home without any problem, but it did it again today, and of course, the shop is closed on Saturdays. What is causing this and has this problem come up before? This car is driving me crazy, no pun intended.

Problems like this cause hair loss for all involved! Best I can say is that the transmission upshifts based on input from engine load (vacuum at intake manifold) , speed, rpms, and throttle position. The info gets sent via electronics, vacuum hoses to electronics or cables, and speed is sensed with a speed sensor. So I guess any of those could be at fault or perhaps a mechanical problem with the trans itself but if it doesn't show up or act up for anyone that's where the hair loss comes in!

I would take a hard look at all vacuum hoses and vacuum items first. Then I might suggest getting the fluid and filter changed which won't hurt it but may not help. Check all wiring connectors that have anything to do with the transmission as best as can be done.

That's all I can think of without just randomly tossing parts at it hoping to stumble on the fix.

Good luck and please post back with what the problem was. This too will get fixed in time,

T
Tom Greenleaf - MetroWest Boston - USA
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http://www.autoacsystems.com/tomgreenleaf/