94 Camry 150K miles. Speedometer has not worked for awhile which is an issue but a more immediate issue just arose that may or may not be related to speedo not working. Engine runs fine in neutral and park and will rev up fine, but when I put it in drive the engine hesitates, spits, does not shift at proper speed and occasionally stalls. Will restart no problem. Here's the weird part (to me at least). When the vehicle is behaving this way (and only when it is behaving this way) and I rev it up in park, the speedometer will jump between 10-20 mph and the trip odometer advances. Recall that ordinarily speedometer does not work at all (but odometer and tach and other dash instruments always work fine). This new issue just started even though the speedo has not worked for a few months.

It does not do this all the time. Yesterday it would not run right. This morning I drove it around 25 miles and it ran fine the whole time and when I put it in park and revved the engine the speedo and odo did not move (as they shouldn't). Engine temp does not seem to be a factor.

I'm thinking maybe a sensor or the speedo itself?

 

Poking around under the hood I just noticed that my temp vacuum valve has broken off, not sure how long ago but it looks like it's been broken for awhile. I know I need to replace it but from what I've read I don't think this is directly related to my issue, but maybe...

 

Vacuum leaks can do weird things, so yes, start there.
Your speedometer sounds more like a wheel speed sensor issue.

 

Yes I wil replace TVV but that has been broken off for awhile whereas odd behavior started just a few days ago.

And yes, I think speedo not working is due to the mechanical sensor located on top of the trans housing.

 

Does anyone have any idea regarding the cause of the intermittant symptoms I described in my original post? I replaced the thermo vacuum valve but the problem persists. Engine runs rough and occasionally stalls but restarts easily. At the same time if I put it in park and rev the engine the speedometer and odomoter both move even though I am in park. At other times both symptoms disappear and car runs fine. Engine temp not a factor.