strange issue with my 92, when it rains or when it's cool out when the shift from 1 to 2 is made the converter locks instantly,in the afternoon when it's hot out no issues.Also first thing in the morning until it goes into closed loop(3 to 4 miles) it's fine.
I have cleaned and dieelectric greased all connections from the tranny to the pcm, overdrive button works fine,no erratic speedo readings and no codes.
Also yesterday I installed a switch in the converter lockup circuit just after the pcm and am able to unlock the converter so it appears for some reason the computer is commanding this behavior instead of a wiring issue any ideas?

 

Could you define "no codes"?

 

Also, if you're looking for information using the incorrect term e40d you won't get much info from the searchs, the transmission is an E4OD, that's an "o", not a "0".

 

No fault codes present in either koeo or koer with modus scanner.

 

I have a 1992 as well and I remember having an issue like this. My solution was that even though I replaced the MLPS with a new one, it was defective. Returned the bad one got another and problem solved. I must say that in my case I did have a code for the MLPS. Hope it helps!

 

I was headed down this direction, I am glad you jumped in with the suggestion.

If the OP does replace the MLPS they will need one as part of the upgrade kit. Ford changed the design in 1994 which requires a new style connector.

 

I was thinking in this direction myself but am trying to figure why? I really am having trouble wrapping my mind around a 10 to 15 degree ambient temp change causing this? I know the mpls is a string of resistors but no matter the gear position the pcm SHOULD lock the converter based on load and speed considering the lockup can be commanded in any gear but low.
Again I agree it is probably the culprit just trying to figure out why? I'm just curious about cause and effect.

 

The symptoms you mention originally were the same ones I had. Changing the MLPS solved the problem. I had to re-pin the new design connector for newer sensors. The old design was prone to accumulate moisture/water messing the inside and probably the source of your problem.

 

Another thought is a problem with the TPS. The PCM relies on accurate throttle angle data to calculate shift points and converter lockup. Use a meter, DVM or analog, to measure the closed throttle voltage. It should be in the 0.6 to 1.0 VDC range. The slowly open the throttle (engine off/Key on) while watching the output. It should increase in a linear manner to ~4.85 VDC. Watch for dips or peaks in the output signal.

I also highly suggest you check the TPS connector for signs of corrosion. My old 1992 F350 was exhibiting some intermittent high idle and rough shifting that was found to be caused by green corrosion in the connector.

For reference: Fuel Injection Technical Library » Throttle Position Sensor (TPS)

Some sensor information from Steve83: http://www.supermotors.net/registry/media/485085