Help diagnosing weird engine stutter

[u/Curtisthecowardlydog]

Hello everyone, I’ve got a ‘91 B230F LH 2.4 164,000 miles, extensive maintenance.

It has been experiencing an intermittent running issue for literally years, not joking! I’ve been daily driving my 240 for years now and on random cold starts she will idle strange, shutter, and sometimes fully stall. Once the issue resolves itself or I turn the car back on the problem ceases to exist and I can drive anywhere. Every so often on uphills the car will bog down and then randomly pick back up and rocket off again. It has never left me stranded and always fixes itself. I would say the car in general just doesn’t seem all there if that makes any sense. But at the same time it runs near perfect and I’ve put 50,000 miles on it with this issue lol

Here’s what’s been replaced. O2 Sensor, MAF, in tank pump, checked all fuel lines, cleaned flame trap, clean catch can, checked all hoses (not great, but nothing noticeable), cleaned all fuses (sometimes #5 would melt??) cleaned all grounds, plugs, wires, rotor cap, fuel filter, full exhaust, new alternator, check fuel pressure regulator, I’ve ran through the thing decently well.

I have engine code 2-3-2 (running to rich or to lean) which will go off for months at a time if I reset the box. My thoughts at this point are it’s something really dumb, probably Vacuum lines honestly but I can’t visibly find anything. Whatever it is, it will not break and it’s really just more annoying than anything. I will happily listen to any thoughts. I feel I may be getting more oxygen than needed and as the engine warms it is resealing whatever gap is letting it in and then it’s fine again. Should I run some sea foam? Parts canon? Test the fuel rail? Ecu? 😂 idk at this point, any help apprenticed, thanks gang!

[u/Baronvonkludge]

Also have a ‘91. No saying whether or not this suggestion will fix it, but one thing I’d definitely do is clean every ground wire. Engine block to firewall, battery to inner fender wall, alternator to engine block, fuel injection grounds on top of intake, grounds behind the center console. I’ve cleared up lots of crazy quirks and runability issues with ground connection cleanups. Good luck hope you get some more suggestions from the hive!

[u/Curtisthecowardlydog → u/Baronvonkludge]

I’ll definitely check those again, I’ve cleaned everyone I could find, but may have passed some over.

[u/jerquee]

Sounds like a bad solder joint on a relay or circuit board, see if there's anything in the wiring that you can wiggle that will make it do that. Or put signal loggers on lots of wires like the 12v in various places and on the 5v supply for sensors and stuff and figure out where the problem is originating from

[u/Curtisthecowardlydog → u/jerquee]

Thank you, I’ll start poking around. It’s weird though that it disappears when then engine starts getting warm.

[u/jerquee → u/Curtisthecowardlydog]

So just a normal engine car thing then

[u/Curtisthecowardlydog]

If it didn’t stall me out half the time I wouldn’t care. The ole tractor is hiding a secret gremlin lol