This condition came on suddenly at a stop during a short errand, not over time.
On cold start, tran in park, emergency brake on, feet flat on floor, RPM at 900. Pull into R, RPM will increase to 1000, tran does not engage. Pull again to N, RPM will drop back again to 900. Pull into D, RPM will again increase to 1000, tran will not engage. Let engine warm 2 or 3 min and tran will "loosely" (will slip a bit until RPM increases over idle) engage at idle but RPM will still increase briefly from P or N before tran engages. Never seen RPM increase above idle before on an automatic. As if engine decouples from trans completely (not turning trans) ?? ideas on cause? sticking trans valve body?

 

Engine idle is controlled by something called the IAC valve which responds to gear selection. The engine may be idling up in response to the expected increased load of the trans. If the trans is not engaging there is no load and thus the higher RPM.

The bigger issue is the trans not engaging. Make sure the gear shifter at the trans is moving in sync with the one in the car and in the correct gear selection.

A sticking valve can cause this issue.

How is the trans fluid color and condition?

Have you tried manually shifting through the gears?

 

Yes the engagement is the issue, although I thought the "flare" might shed some light on what was going on inside. You would thing that if the IAC were causing it you would see the same thing to some degree on properly operating trans? There is always a transition time from Park to reverse, but I've never seen an rpm flare during that time. Anyway....... the fluid is full, very dark and definitely should be changed, but does not seem to have a burned smell. I did not test drive, or try pulling codes. I only drove back and forth in driveway to check and note behavior. Do these have modulator valves? If there is a sticking valve body, do you think changing the fluid will free it up? I don't promote snake oil, but wonder if it would help dissolve varnish or whatever buildup may be sticking and soften seals? Do the solenoids affect initial engagement or only determine shifting? I am now 500 miles from car and my son is capable but has not done any trans work to date. I would drop and clean pan and magnets, replaced filter, then fill and flush through radiator line. But........is that a likely remedy? Trans shouldn't be worn out. Never hard acceleration or driven above about 2500 rpm. Thanks

 

The engine computer is wired to the gear shift switch on the trans to know if the shifter is in P, N or a gear. Based on this it adjusts idle. Could be engine idles up when shifted into gear, but if trans not engaging then no trans load to bring idle back down to normal.

As to trans.

What engine V-6 or 4-cylinder?

Does this lack of movement occur in all gears and reverse?

A rare event but determine if the parking pawl is not disengaging. Place shifter in a gear and determine if the car be easily pushed.

Also has happened the brakes lock up.

It is possible the manual shift valve(s) is sticking. There are little ***** and shifting pistons in the system which might be sticking.

Or the torque converter one-way clutch is bad.

Or?

If fluid bad enough it may plug up the filter screen but this would be very rare. Or the screen could have come off (extremely rare).

The trans shifting is electric via solenoids however there trans can be shifted manually with shifter. The shifter body responds to both solenoids and manual gear shifting.

The in car gear shifter uses a cable to move the shifter arm on the trans. Make sure the cable is not broken or some other problem.

I can't state for sure what the problem is. You can try a complete change of fluid but this may not solve the problem.

This type of event is common and tends to occur due to lack of fluid changes. The manual valve starts sticking, a clutch wears out, then one day no forward or reverse.

With some component failures, reverse or forward may work but not the opposite direction gear.

The trans has codes but only for solenoids and speed sensor.

Send engine model as trans is different for engine model.

 

This is a 5SFE engine. Unfortunately? all the external mechanics check out. Linkage, etc. Car rolls easily on a slight incline. When dead cold, will not engage any gear at idle. When at normal water temp. gears will engage at idle (after a delay) enough to drop rpm, but needs a bit more rpm to fully engage. Discussed with service mgr at local Toy dealership this morning and I think a valve is sticking in a position that allows fluid to escape thereby reducing pump pressure so that the clutch pack doesn't engage or fully engage. The reduced fluid restriction allows the pump to turn more easily and the rpm to increase. We are going to start by changing fluid, exercising the manual valve, driving a bit, then changing fluid a second time. We'll see if that cleans anything up

 

There are transmission products claiming to clean trans. Many need the car driven for a number of miles but the one at the link claims something else.

Ends sticky transmission valve shift problem. Add; driving ends sticky shifting

If this is snake oil, who knows. You might consider adding a product like this to the current fluid, then run engine to circulate.

Some shops will do a flush that included cleaning chemicals but of course if the car isn't mobile this is a problem. Or do a complete fluid change yourself at the radiator line.

If you do get the trans to work, suggest a complete change together with dropping the pan and cleaning. The trans filter screen seldom plugs up but debris can lie on the pan floor.

If the issue is in the control valve body, this can be removed without taking the trans out. It drops out the bottom of the trans via the pan. The key is finding a repair shop that will not insist on a complete rebuild or replacement to make more money.