When I start up cold she runs fine no issues. But once its warmed up if I shut her off for 10 mins or so and start back up it acts like shes running on 4 cylinders. Dont really notice it at idle but under load it shakes a lot. This lasts for 11 minutes then it's like something clicks and she runs smooth as butter again. If I shut the engine off for at least an hour so it can cool down then she runs smooth also. Just starting hot for the first 11 minutes.

 

My first guess is to check the coolant temp sender switch. Got it out and in room temp water about 75⁰ F it reads about 225 ohms. In boiling water it reads about 63ohms. Is that a good sensor?

 

Idk if this is the sender or the sensor?
attached was a gray and red wire. Grounded to engine block

 

Whelp I went to remove the other coolant temp sensor on the drivers side of the thermostat housing. The one with two wires plugged into it. Trying to wrestle the wiring connector off of it the whole top snapped off with the internals. So I went to autozone and bought a new one of those $26 part. The motorcraft one would've needed to be special ordered. Might need to truck tomorrow so went with duralast.
maybe it's in my head but it seems like a brand new truck. Drove it around town seems to have gained another 5hp. Then stopped to get groceries. Fully warmed up engine parked for 15 mins started up and drove home fine. Maybe that's it? Fingers crossed.
I hope 15 mins was enough downtime on hot engine to trigger the condition? I know if I turn it off for less than 5 mins it didn't do it. But 10-30 min range it would. So I'll report tomorrow how it does with other starts and stops .

 

Also truck is '94 ranger 4.0L OHV for reference.

 

Still does it, albeit much less noticeable. And not as long to clear up now with new ECT. Still seems like a misfire when its restarted hot. Clears up after maybe 3-5 mins now.

 

Another clue is its always had a rich in bank 1 and bank 2 code. It doesn't store that code though. Just when I run a Koer diagnostic it comes up with codes 173 and 137. Its always done that since I bought it though. And the rough engine a few mins after hot starting is new. Noticed it a last week or two about the time I replaced my radiator. Pinhole leak in the last one

 

I'm thinking best way to figure this out is to run through the air, fuel and spark systems end to end diagnosing each component.
I think fuel is ok pressure reading was w/in parameters. I cleaned the MAF. So I was gonna check out spark.
As far as I can tell the spark systems is isolated to itself. Doesn't go through the computer. 4 main components. It starts with crank position sensor down near the bottom pulley of the engine. This might be the issue because coolant was spraying right in that area with pinhole leak in radiator.
Next the signal from cps goes to the EDIS. A lil computer next to the battery that controls ignition timing to the coil pack based on signal from crank position sensor. not sure how to diagnose this part.
then that signal goes to control the firing of the ignition coil pack. Then from there it's the spark plugs firing. I might replace the spark plugs because I just put copper autolites in there last year. Think I read somewhere its recommended to use double platinum plugs.

 

I ran KOEO codes again and now I'm getting a code 232. Hanes manual doesn't have that code. What I can find online has either primary ignition coil fault or Edis 1234 fault. Where to go from here?

 

I'm still at a loss. Tomorrow I might try and put the old radiator back in. Maybe the new radiator is causing it? Then maybe take it to a mechanic to see if they have any idea. Might be time to send this one out to pasture?

 

Update. Problem solved. It was a fuel injector. My guess is it was sticking shut when it was hot. It didn't do it while running because it was still moving. But then when I shut it off hot it stuck there.
did some tests after thoroughly going through electrical side and being stumped. I noticed one injector was "ticking" much quieter than the rest. When started hot I couldn't feel any tick at all. I tested resistance 17ohms. Was normal there. But when I ran jumper wires over to it it didn't "click" but made a kinda muffled crunching sound. Other injectors made a solid click.
was a bit a a project replacing that injector. Had to assemble and disassemble the upper plenum twice. Because it didn't seal first time and was spraying fuel like a faucet. I found the 2nd time it's more important to seat the injectors into the fuel rail first then put that assembly down into the lower plenum. That lower seal isnt as important as the top seal into fuel rail. All the pressure is above the injectors in that fuel rail. Below the injectors there is no pressure. Just a vacuum sucking in the vapor as it sprays out the injectors. If the bottom isnt sealed properly you may have a vacuum leaking but you wont get fuel sprayed all over your engine bay.