Engine missing after 100 miles

[Prerun4fun13]

So I'm having an issue with my 94 explorer 4.0 auto 4wd.
Similar problem this guy is having https://www.explorerforum.com/forums/showthread.php?t=438737
but ambient temperature is not a factor, and the truck won't die unless sitting at idle. On the freeway it misses at any rpm under 3500. It also smells super rich.

I just replaced the computer thinking that was the problem but it did not help. I replaced the coolant temp sensor but i think i might change that again just in case. Now I'm thinking oxygen sensors?

 

[natenkiki2004]

Don't just throw parts at it, especially expensive parts. Do a search on this forum and find out how to do a KOEO and KOER test, see if that comes back with anything. If not, do a general tune-up with spark plugs, wires (you can ohm test these), coil pack ohm test, MAF & throttle body cleaning, etc.

If it almost wants to die, it could easily be a single bad spark plug wire. That will kill 2 cylinders. I had bought new premium spark plug wires and less than a year after, I had a substantial misfire that got so bad that I thought the engine would die at a stop sign. An ohm test showed no continuity on one of the wires. Replaced the set and it's been great since. So, you gotta start with the simple, cheap and easy things first.

 

[Prerun4fun13]

The plugs and wires were replaced within the last 5000 miles. To me the problem must be some sort of sensor since it only happens when the truck is driven for 100 miles non stop. Once it sits for a while it runs fine again.

 

[natenkiki2004]

Just to put it out there, I don't think my set even had 2,000 miles on them before one bit the dust. It's something to keep in mind. It's quick and easy (and free) to check wires with a multimeter.

When it starts misfiring, you can ohm test the coil pack and see if there's a heat-induced break/short in one of the windings.

 

[2stroke]

Replace the spark plugs and wires. Look at the old plugs and number them. It sounds like a bad fuel injector to me.

 

[Prerun4fun13]

Replace the spark plugs and wires. Look at the old plugs and number them. It sounds like a bad fuel injector to me.

Ya good call I'll pull the plugs and see what they look like.. I'll post back if I find something that doesn't look good.

 

[malohnes]

If you run the engine rich long enough it will foul the O2 sensor so it would not be a bad call to replace this as well.