outdoorjunky

So I rewired my injectors splices, ended up having to cut out a lot of black non conductive wires. also rewired the starter splices and fixed my cold start problem by rewiring between the injector and the thermo time switch. while I was in there I fixed the coolant temp sensor wiring too that was a mess and the previous owner had splices all in the harness with some of the worst soldering work I've ever seen it's like he'd never heard of tinning a wire or using fluxed solder . After rewiring everything the truck no longer pings and it runs a lot better with steady middle of the road engine temps under all driving conditions plus it starts right up in the morning now when before I'd be cranking it multiple times to get it to go. I still had the damn misfire after doing all of that but I had been running the 007 and 011 valve clearances and decided to set them hot to stock spec today and now the misfire at idle has completely cleared up some of the valves seems really tight too so I imagine they werent closing at the right interval because of it. Now the only problem I have is the misfire that comes on at around the 2k-3k rpm range. I'm changing gears and plan to look at the EGR system again, maybe the thermo vacuum valve is bad or something with the modulator or even the egr valve is opening too early or something because as far as I've read the EGR system starts pulling vacuum around the 2-3k RPM band. beyond that I have pretty much gone through everything else I can think of. what I had/have here is a case of multiple problems with similar symptoms so it made it hard to troubleshoot base on symptoms especially since the idle mis and the higher rpm mis now seem to be separate beasts when I was attacking them as if they were part of the same problem.

Co_94_PU

iTrader: (-1)

Modulator is prone to failure, not aware of any work around or sources for nos parts. It's a big reason people do the EGR delete in my experience.

outdoorjunky

outdoorjunky

outdoorjunky

I wanted to come back through and button up this thread with a resolution. The truck sat for a while while I was in school but now that it’s summer I got a chance to troubleshoot further. Basically I exhausted all other options and then started looking at the cooling system as the cause of the misfire. Even though the radiator was brand new it wasn’t doing the job and was the cause of the temperature spikes when the engine was under load. I replaced that with a 3row and problem solved. The misfire was semi related to the radiator but also the metal heater return pipe had been kinked at some point at the bend that wraps around the exhaust manifold and it looks to have been bent back into place, however, that made a restriction in the bend causing reduced coolant flow. Clearly the coolant temp sensor didn’t like this or it was sending bad singles because the coolant temps were off due to restricted flow. I didn’t realize the pipe was wrong until I was pulling parts off a 22re at the junkyard and I noticed the heater return on that truck didn’t have the same bend mine did. I pulled that heater return pipe off the junkyard truck, cleaned it up, and installed it and the misfire was gone.

It’s so so weird how sensitive these engines are to coolant temps and air in the system. I went through just about everything on this truck that could cause a misfire and learned a lot about the systems in the process but it’s sucks that it was partially a brand new part causing much of the issues.

I have to give credit to Roger Brown aka 4crawler for suggesting I go through the coolant system again.