I currently have a 94' Pickup 2.4-L4.
I've been having issues with it for a while and can't seem to figure out what is the cause. When I come to a stop the engine idle drops to about 900 rpm and then dies (to avoid this I have to keep it revved to 1500 rpm) I know something is making the engine run rich. I use a paper clip to jump the diagnostic jumpers and I get a code 21 (Overheated 02 sensor which has been replaced) 25 (ECM detects engine running rich) and 26 (ECM detects engine running lean). I haven't found any vacuum

Current millage is 192,600 but engine has been having issues since 187,000 with previous engine rebuild at 175,000
Parts that have been replaced o2 sensor (Denso), Distributor with new wiring, TPS Sensor, Timing is set to 5 degrees (which I don't believe is right)

Suggestions or questions?

 

Welcome to YotaTech.

Spec idle speed is 850, so 900 is close enough. Will it not idle, or is your problem only when stopping? If only when stopping, you should check the brake booster line for leaks.

Code 21 is not an "overheated" O2 sensor, it is an open or short in the O2 heater circuit. You may have some stored codes, so let's clear those first. Remove the EFI fuse for about 30 seconds, and replace it (if you just pull the battery cable, you'll lose all the radio pre-sets). Check for codes. Then drive around long enough to warm it up, and check for codes again.

 

After it's warmed up, unplug the electrical connector to the cold start injector.

 

Found a partial fix this morning. I replaced the PCV Valve which helped my dying idle when coming to a stop.
Code 21 and 26 were erased after the battery reset thanks to @scope103 !

However I now and still have code 25 which came back after a 40 min drive. Fixes for a code 25?