Oh wise ones, I need some help, some wisdom.
That 97 4.0 has been running like a top ever since I got it. 300,000 miles, one owner, extremely well maintained, now 320, and I didn’t think to tune it up until I had a miss coming back from Ford nationals in June. Actually, I couldn’t really feel a miss, but I feel like I had a slight loss of power. It’s still runs very strong, but doesn’t seem to run as strong as before, but it might be in my mind.
When I got home, the left exhaust pipe was full of soot, and there was soot on the rear fenders on the left side. A lot.
When I pulled the plugs, the driver side front spark plug was actually loose, it was still in the threads, but it was loose enough to wiggle it and remove it with my fingers. When I pulled it out, it was covered with soot. I put the new spark plug in, and it tightened down like normal. I don’t remember ever having a loose plug in the last zillion miles on any of the dozens or hundreds of vehicles….
I put in new plugs and wires. I haven’t put in an I haven’t put in an PCV valve yet, but I find it hard to believe that would be the problem. After driving it a couple hundred miles at highway speeds and temps,, I still have some soot in that left pipe. Left compared to right, today.
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Last week, I ran the gas tank down to less than a quarter tank, and I put in a can of seafoam. I ran it long enough to make sure it was hot and all through the system, and then I parked it for a couple days. Then, when I was almost out of gas, I filled it with premium. I don’t think that made any difference. I have a few hundred miles at 70 mile an hour at highway speeds since changing the plugs.
It seems to be hitting on all cylinders, but it still seems to have a slight lack of power. Not a dramatic lack of power, just a little from the way it was running when I got it. I can’t tell if it’s got a miss at lower RPMs, but I do still believe there’s a lack of power. I’m not sure if the miss is in my mind.
Today I pulled that spark plug, and it looked fine.
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I’ve wondered off and on if it had a blown head gasket, but it just runs too well. For unrelated reasons, I took the top radiator hose off a couple times, and it always takes checking it after some miles a few times to get the radiator topped off. But I think that’s because there’s no good way to burp it, not because it is consuming radiator fluid. It was full when I checked it today after a couple hundred miles.
So here’s my need. What do I check next?
I’m going to buy the gizmo to do a compression check. It’s in the mail. Btw, it’s not using any oil I can notice.
Could I have fouled the catalytic converter on that side? That cat has less than 10,000 miles on it. I understand the science, and if I was feeding hydrocarbons into it when the spark plug was loose, once I fixed it, running at highway speeds and temps, shouldn’t it burn off the carbon off fairly quickly? Before, when I’ve had a cat that was plugged, the vehicle ran like absolute crap. It’s still running pretty good. ???
What else can I check short of pulling heads?