Hey everyone!

Been using this forum for over two months as I slowly build out my 1990 F250. The threads here have been invaluable as trying to find torque specs, pressure specs, and other troubleshooting and building specs anywhere else has proven impossible (even my Haynes guide doesn’t know some of the stuff I found only here)!

Finally made my own login to ask for some help/ideas.

I got this truck and it was pretty corroded. That said it started right up and ran beautifully. It did occasionally flash a CEL but very intermittently. Picked it up, and have enjoyed getting back to my roots (had almost the exact same truck in High School, just older) and slowly getting it back to good running order so I can start playing with it as I build it out.

Something weird about it though: after getting it, I did a full tune up and after it started stuttering. Dizzy cap, plugs, wires, coil, ignition control module, thermostat, all fluids (literally all, the factory rear end fluid was a special stink that is still stuck in my shirt I was wearing at the time. Though of note I did not drain the torque converter, just dropped trans pan), all filters, rebuilt the vapor system, all new sensors (except for rear anti-lock sensor), new manifold back exhaust (used a modern heavy metal cat that is designed to not need the air system), and a bunch of other stuff that won’t be related to my problem.

Of that, I did the following in one session: the complete ignition system, oil change, trans pan and fluid dump and filter change, (again I did not drain the torque converter), rear end fluid, and fuel filter. As I was going on a test drive afterwards, I noticed that the truck was idling slightly more rough (going from no in cab shake to being able to feel the engine in the cab) and it had developed a slight shudder at around 40 mph until I hit 60 mph and around 900-1700rpm. I also had the cat die on me and start the rattle to death (which I thought was my trans filter not the cat rattling because I was worried I didn’t seat the trans filter correctly and it had fallen and was rattling in the pan, lol. Paid for a tow for nothing). Important to note, before doing that tune up, I had no stutter at any speed or RPM.

I ran codes and KOEO and KOER and the only code that pops up is 33 EGR failed to open. To make sure EGR wasn’t the problem, I blocked off the inlet and removed vacuum. I confirmed that the egr is fully closed as well and as such the sensor should be reporting fully closed. Shudder remains (I am planning on rebuilding the full EGR system, but will be getting headers and a new intake soon, so figured I would just wait till then when I don’t have to force a corroded pipe from the manifold).

I have replaced every sensor on the truck, (and they all needed it) and it helped (though didn’t fix) the idle and shudder. It runs wonderfully in WOT and at lower speeds. Amazing power, and a 0-60 of just 10 seconds. Attempted to test fuel pressure and the test port is so corroded that I couldn’t get it to open for the test. I don’t think it’s injectors or pressure though. Timing is set at 5 BTDC, but the distributor is stuck and cannot be adjusted. Timing advance test shows full 20 degree range of motion. Timing is steady and doesn’t fluctuate.

I have noticed a occasional slightly smelly exhaust stink. Not rotten eggs, but just something unpleasant. This was noticed after tune up before new exhaust, but it continues with new exhaust. Additionally, I have noticed that when I have overdrive off, or when I make the torque converter unlock the stutter stops, though I don’t know if that is because it sends rpms above the stutter range, or because the torque converter is the cause. The stutter is not uniform, and is quite random. It doesn’t sound like pinging.

And so, I ask you all: any ideas what is left to troubleshoot or test? Any ideas on what could be the cause? Any ideas on how I could isolate and see if the problem is transmission specific or engine specific?

Thanks!

 

Could you please explain the "stutter" better? When? How much?