I replaced my capacitors and did about 5 miles yesterday and no skips or hiccups at all so far. I have a bigger drive coming up this evening to really test but were looking good so far!

 

upon a closer inspection of ECM capacitors, one was obviously leaking/ failing. After replacing all three the van runs great with no misfire. I’ve been fighting this thing for so long it’s hard to believe that it’s fixed but I’ve ran it through the paces and all is well.

 

Ah man. Unfortunately for me after a few miles it came back and seems to be behaving much as it did before =/

I have a bunch more troubleshooting to do when I can find the time. Unfortunately no one seems to know the systems or have the right diagnostic tools anymore so I dont even feel good bringing it to a mechanic since I don't have the time.

I contacted a couple shops and they immediately started telling me they wanted to throw parts (already replaced parts by PO mind you) at it =(

 

With the 94 which is OBD I , you had to know how to do the tests, all of them because codes did not do any more than point to the system with the problem

OBD II was much more specific and helped a lot because the data stream info was available now and you still needed to know what you were looking at in order to proceed with further tests. Either way replacing parts without verifying they were defective or malfunctioning can get very disappointing.

If you still have the ORIGINAL problem, please describe it and the driving conditions present at the time the problem appeared and check engine lamp illuminated.
For the 96 vehicle , a capable scan tool and knowing how to use it, should help direct us to the system with a problem.
If possible please post the data stream info (Eng temp, RPM, fuel trims at what speed, O2 sensor readings TPS, MAF rdgs) and other info your scan tool provides.
Thank You.

 

Yes I'm on ODB1 so unfortunately have basically no insight haha! Last time I checked there were no codes - I bought one of the little Innova units which should be delivered soon to recheck.

Its a 1994 model ClubWagon with a gvrw just shy of an e350. 351 E4OD and very standard / unmodified. ~120k miles.

The issue is a slight little hiccup kind of misfire. Seems to be more acute when cold - but can flare up when hot also. It frankly feels to me like the ignition drops out for a split second... randomly every so often. Could be every second or two for a bit - could go an hour on the highway before noticing it at all. It is very noticeable under load - not sure if more common under load or just very appearant.

PO replaced a bunch of sensors. Auto-Zone level replacements of MAF, TFI, TPS, coil, whole distributor, maybe more. I replaced the coil with a new Motorcraft after seeing what looked like potential bad insulation. I also did plugs and wires myself as that hadn't been done. No changes on updates.

I have a video of it performing at idle here that i posted with regard to a Reddit conversation on the issue.
I've checked the sensor ground at the computer and diagnostic plug. Seemed to be in range but an item I'll probably recheck a time or two.

edit: also no CEL is on currently. Also remembered the PO said he had changed the in-tank fuel pump and sender as well - which fixed nothing but now my gauge is inaccurate =(

 

Are you aware of the way spark plug wires should be routed ? If you routed them neatly so they look nice you can create problems . Certain cyls need to be kept separated.

 

I've never had a smallblock be uppity after I've swapped wires but I'm prepared to be wow'd haha. Changing the wires to a new Motorcraft set on this motor didn't change the behavior at all. I don't OCD them in place or anything - just out of the way of the exhaust and the normal stuff.

I haven't found a reasonably priced FSM yet - is there an image available of what areas need to be deliberate?

 

Find a pix of your vehicle's engine showing firing order and cyl #s. Plug wires for 2 adjacent cyls in the firing order can create problems by way of mutual induction, and those particular wires must be separated and not be allowed to run parallel to one another.

For example; if cyls 7 & 8 are next to one another in the firing order those two plug wires MUST NOT be placed next one to the other. Looks sloppy , but must be so.

 

I updated as you & the bulletin described (I hadn't followed best practice) and got quite excited when it idled nicely. Got on the road and within a few seconds it started misfiring hardcore / worse than it had thusfar.

I did finally get my scanner - got a 212 so decided to quit spamming OP here and started a new thread dedicated. https://www.fordforum.com/forum/ford...76/#post136754

 

You're absolutely right about the importance of separating plug wires for adjacent cylinders in the firing order. Mutual induction between those wires can indeed lead to performance issues. While it might look a bit untidy, ensuring they don't run parallel to each other is crucial for preventing such problems. So, when cylinders like 7 and 8 are next to each other in the firing order, it's essential to keep their plug wires well apart. It's a small but significant detail that can make a big difference in the engine's performance. Thanks for highlighting this important tip!