Alright, I got the 2.3 lima in my 93 ranger, (1?)80k miles, its been running rough, I cased some possible mechanical issues but found non- at least non that made er run better

symptoms: flairs to 3k for 5 or so seconds on cold starts, will hover high for a while and slowly drops- she likes to high idle (1.2-1.5k), but will eventually settle down to 700 rpm- although shes runnin real rough- exhaust pulsing, distinct “puff-puff” exhaust note when behind the truck, randomly she’ll drop to like 500 rpm (sometimes lower) and will be running really rough, but I’ll typically give er some throttle and she’ll bounce back to high idle

will be surging, seems like its getting worse, while idling at 900 she was bouncing up or down by 100

she diesels on shut down- takes about a full second to shut off when key is turned

has no reaction to o2 sensor being unplugged (have only tested while idling around 700)


now- I don’t have a great understanding of diodes- I was playing around and wiggling the wiring harness trying to find potential issues- after finding nothing moved to the fuse box- I was wiggling all the fuses and nothing happened until I touched the diode, as soon as I touched it it was like someone briefly stabbed the throttle making her jump up 200-300 rpm suddenly, I could occasionally get it to replicate by pushing the diode up and to the right (like towards the relays), I took the diode out, the pins on it were dirty so I took a wire wheel to it and cleaned it up, put it back in and she ran the same but now I cant replicate the jump in rpm when wiggled

i took a small file to the sockets for the diode, got some of the corrosion off so you can see the bare metal but still no affect

pulled codes though it showed no CEL while running, flashed 558 (I have a new IAC on it) and 111

I put my multimeter on the diodes pins while running and it showed .80 occasionally bouncing to .81

would love to understand exactly how diodes work, how to properly test and interpret those results