Ford E 150 intermittent miss with intermittent transmission issues

I recently bought a 94 Ford E 150 Chateau van with 84,000 miles on it in very nice condition except for an intermittent miss. It has a 5.8 V8 (351). I figured start with the basics re the miss since it had a brand new emissions sticker I thought it wouldn?t be too difficult to rectify. It now has new plugs, plug wires, fuel filter, air filter and a serpentine belt which needed replaced. We tried new ECM?s on two different occasions but it still misses. The oil has been changed to a synthetic and I have been adding Ethos fuel reformulator.

So here is where it gets weird. A week ago I towed a buddy?s enclosed motorcycle trailer to an auction trying to sell one of my vintage Hondas. It was a hot day and the van started running on the hot side. It didn?t overheat but it got to the point where I was running with the heat on and the windows down. After I unloaded the bike I let the van cool down and the return trip (about 60 miles) it ran fine. No misses and ran cool towing the same trailer less about 300 pounds. My thought process was that due to the low miles it just needed to be run and the added load burned off some sludge or buildup on a valve. The following day we left for Norfolk, VA and took the van. It ran perfect for 800 miles over 4 days although when it was running fine the transmission seemed to shift harder, particularly into second gear.

The saga continues. The day after we got back from VA we picked up a used popup trailer to do some camping. It probably weighs about the same or a little less than the bike trailer that ?cured? the van in the first place. We got the trailer home and I had to do some finagling to get the trailer into the warehouse (another story) but long, story shorter, the van had to do some work. It started missing again. I have only had it on short trips since although long enough to get into normal operating temperatures but is now an intermittently missing, normally shifting van.

So my question is has anyone heard of anything like this? I was prepared to do a valve job and then an 800 mile perfectly run trip with the added variable of the transmission acting differently has me wondering. Any help/leads/thoughts/prayers/incantations would be appreciated.

First, I would stop adding anything to the fuel, that is just draining your wallet. Have you checked the vacuum? Also do a compression test on all cylinders… Also check the alternator’s AC ripple. Just a few ideas.

I definitely support the idea that you trace and check every vacuum line, especially the ends that push on to a nipple. They crack over time and a vacuum leak could cause all of this.

As I read it you have a intermittent misfire that doesn’t set a check engine light. The misfire was steady enough at one time for you to be able to “stub” in two different ECU’s but it still misses.

I also like the vacuum leak search idea, pay attention to the sealing area of the intake. Is the intake 2 pieces? perhaps it is cracked and that is the reason the condition seems to be temperature related.

Don’t jump into the valve job idea, you have not reported symptons related to poor valve sealing. A broken valve spring is a way out there idea if you needed one.

One test you should do along with a wet/dry compression test is a manifold vacuum test. We want to see if it is high enough and steady.

If you had not already replaced plugs/wires I would suggest you spray with a spray water bottle around the secondary ignition wires (searching for a spark)

If you look at the back of the radiator and see fins that have corroded away, you need a new radiator. If you see lots of white or green on the radiator, just change it. The van is old enough to have this problem.