Something is still not right with my Expy's 5.4l. It's not the same as it was. I put all new coil packs in and while I can feel a noticeable improvement a slight hiccup remains. When the motor is cold is there's still a slight flutter. If I start the vehicle and put it in reverse, as soon as its in gear I can feel a "tap" in the wheel. After the engine starts warming up and gets to operating temperature I don't feel it as I'm driving down the road. When I come to a stop sign or stop light, rpms drop to 650-700 range, motor is very smooth - no surges in rpms, etc - but I can hear through the engine that same slight split-second of hesitation. It still feels like one cylinder isn't receiving a good spark or something. But it's very very light. If you pop the hood and look at the engine, you can't tell there's anything wrong. However, I know these modular motors are like sewing machines - nice, quiet, and hums along; very smooth.

I found that coolant had indeed leaked down around cylinder 5 from the thermostat housing. The boot came out wet and right away I knew that was the main source of my problem. There was coolant down and around the base of the plug. Now since the motor tips down and back toward the firewall, coolant has a very nice path to follow and can hit all the plug wells on the driver's side. Number 5 was soaking and number 6 had a little coolant around the boot - but not all the way down the boot toward the plug. 7 & 8 were fine with only some coolant on the top of the boot seal. None in the plug wells.

Anyhow I blew the plug wells dry, inserted a new COP in every cylinder, and went on my way. As luck would have it, I still have a friggin flutter as described in my first paragraph. Granted the miss/flutter/tap isn't nearly as bad as it was before I changed the COPs and sealed up the thermostat housing, I still sense something isn't right.

So my final thought is that one plug must be fouled. Logic dictates that if anyone is bad, it must be #5. I pulled that this morning and replaced w/ spare and here's what it looked like:









What do you guys think? The problem seemed to lessen with a replacement plug - but only marginally. Should I pull number 6? Logically, if #5 received the grunt of the coolant and was part of my missfire, #6 might be fouled as well since it received a little coolant too? I did drive around and put +/- 150 miles on the truck with the miss before changing all the COPs so I'm wondering if driving with the miss for that long wreaked havoc on the plugs due to the coolant leak? I'm guessing that as the plugs get hot along with the engine, the carbon build up doesn't have as much of an effect and therefore can fire better?

Thanks

 

What do I think? I think that I'm flabbergasted that someone would go through all of that work to change all of the COPs and not change all of the plugs at the same time.

 

I didn't because the plugs have only 5k on them. I'll admit that during the process I didn't think the plugs would have been affected that much so I didn't pull them.

 

With only 5K on them I can understand why you might not change them, but at the very least they should've come out to be inspected and cleaned. There might be a second cylinder that is misfiring and a blackened plug would've tipped you off. Hopefully it's just the #6 plug giving you the balance of the problem so that you don't have to pull the rest back out.

 

You are correct. I should have pulled them to inspect them all while I was there. So far I have replaced #6 as of 15 minutes ago. 6 looked exactly like 5 did in the photos. A little white but no black. Since #6 is easy enough to swap plugs in without too much disassembly, I replaced it with a spare I had. It was pretty clean and the gap was good so it's there as an experiment. I'm hoping that cures it. When I started it, it felt pretty smooth even when I dropped it in gear. I'm going to take it for a good drive tonight so I'm crossing my fingers I lucked out.

My gut feeling is if its one of the cylinders, it's going to be on the driver's side since the coolant leak was there at the housing. It ran fine until that leak developed so I'm going in order for cylinders.

 

it could be the spare plugs just get some new motorcraft plugs