selective no start issue

[capn_r]

Long time lurker, first time poster. I have a 91 EJ22 (na) from a FWD automatic sedan swapped into an 88 GL10 wagon that is FT4WD.I have gone over 60k miles since the swap with zero issues until the last few months when it began randomly not starting. When it starts it runs great with no bad habits that I can detect. It has a code 31 and I haven't yet checked the various resistances and or voltages in the test procedure for the TPS. (I have another intake manifold that I may pirate the throttle body/ TPS from and swap on when it quits hiding from me) I did flush some carb / throttle body cleaner through the IAC and since that it has only not fired once (but did the next time I tried it with no changes to anything) When it fails to start it just cranks and don't offer to fire, then the next time I try it it may stumble a little before firing but then it cleans right up and runs fine. It usually does the no start thing after setting for two or three days, and fires off every time with a shorter downtime. (such as overnight) Temps range from the low twenty's to the mid forty's(F) when it has selectively acted up. I have searched here and over at USMB but didn't figure out a clear solution so I thought I would ask. I hope I am in the correct sub-forum. Thanks!

[Legacy777]

Welcome to the BBS.

When was the last time you've replaced the coolant temp sensor, or has it ever been replaced? How many miles are on the car?

Is the code 31 a stored code in memory, or is it an active code, ie the engine light is on all the time?

Was there anything done to the car around the time it started acting up? When it does run/start up, are there any other oddities you notice with how the engine runs? How is your gas mileage?