2004 Ford Ranger - Lugging/Low Power

At 212 k miles, there is a low grade lugging, like a random misfire, most noticeable at 60 mph. I’ve replaced plugs, wires, coil pack, fuel filter. Fuel pressure is good, injectors are firing.

Is a check engine light on? Have you run a compression test on it? With that many miles, could just be worn rings and valves. A compression test will show that.

Have you solved this problem yet?
I’m having a similar problem, but usually at lower speeds especially when cold.
It’s been getting worse the last year, but still no check engine light… and only 320K miles

First step is a compression check; other than connecting a vacuum gauge that is. A vacuum gauge could certainly let you know whether or not to proceed with a compression test.

An engine in good mechanical condition should show 20 to 21" with a rock steady needle although a bit lower is fine if at altitude, etc. Much lower and/or a wobbly needle means it’s compression check time and based on the high miles I would not be surprised to see a mechanical fault or two.

what motor is in truck? 3.0? 4.0?

The vacuum has been 20+ since I put the gauge on at about 100K miles.
The compression was around 150 on all cylinders as of about 10K miles ago.

It’s got the 4.0

The compression numbers are on their way down at 150 but for 320k miles that’s very good., Iff the vacuum gauge needle is at 20 and holding rock steady with NO fluttering that is also good.

Plugs, wires, and so on good? One possibility is that one or more injectors may have clogged screens and are not allowing sufficient gasoline to pass through when the injector opens. The fuel tank sock in the tank catches the larger debris, the fuel filter strains it on down, and the tiny screens inside the injectors are the final filter. The only way of cleaning those is by removal and reverse flushing. That is cost prohibitive.

Since you have a vacuum gauge do you know how to read it for a partially obstructed converter, etc?

Plugs (iridium) were replaced when the compression check was done. The wires are original, but all test within specs. I had the injectors rebuilt at around 250K, although they said they didn’t need to be as they were still ‘good enough’.

The converter has also been checked and is good.

I’m beginning to think it’s an wiring issue as a few times lately when I hit a particular bridge expansion joint it seems to also stutter…but wiring can’t be chaffed after only 22 years and 320K miles, can it? LOL