Trans wont stay in drive unless accelerating
 

For the last 50'000 miles my SVX has wanted to downshift to the next lower gear for no reason. always when cruising at speeds up to 80mph with light pressure on throttle or cruise set. when in drive it will drop into 3rd than right back to drive. If I have it in 3rd while driving slower it will jump to 2nd and than back to 3rd. when in 3rd I can press manual button and it will stay in 3rd. above 80mph in drive it doesn't act up and at higher speeds in third it doesn't act up. Some times it is much more active than others.

I remember reading that someone on this site had same problem and the tps was at fault.

what are the symptoms of a faulty tps?

Other than the above problem trans is fine with firm quick shifts normal fluid color and I change fluid every 10'000 miles when I do my oil changes.

Someone just posted a note no how to easily diagnose a bad tps and how to give one a simple tune-up.

It was Trevor in New Zealand
 

Check on Trevor's posts with search, you will find it. Very useful info.

Joe

Did adjustment of the TPS help?

I ask because I replaced my TPS AND adjusted it (twice). Using Trevor's approach, I changed the value a bit just to see if it mattered (changed from the 0.491V it was at, to 0.505V at closed throttle - at least that's what my DVOM showed). My car has the same symptoms mentioned in the original post - but only in a weird way - here's the deal.

When cold (for Florida anyway) the transmission up shift is less positive than when warm while in "D". So, I usually start out my morning drive in "3". The shift behavior from 2-3 is definitely crisper this way - no idea why. Also, if I start out in "d", I sometimes feel like the 3-4 shift slips a tad - no flare or anything - it just doesn't "feel" right. I'm a little paranoid about the tranny, so not sure this is just a cold start thing or a mental misgiving on my part?

OK, so now when having driven maybe a mile or two I shift into "D" and all is well. However, sometimes I forget and leave it in "3". Then when the engine has reached full warm, the transmission will start the behavior - feels like it's trying to downshift to "2" under little or no throttle conditions. Quarter throttle or more it's OK. Best description of the conditions is when slowing down like a traffic light ahead has turned green and you're letting traffic get up to speed in front of you.

I haven't changed anything yet. when it starts acting up I shift to 3rd and lock it there with the manual button. It doesnt start acting up until after the engine and trans is warm. Some days it will stay in d just fine with no problems.