skykingjeep

Hello all, I'm at the end of my rope... almost.
The long and short of it, 1995 4.0 straight six 155,000 miles:
When the engine is cold, it runs great. Floor it and it flys down the road without any problems.
However... let it warm up and when it's floored it starts missing around 2500-3000 RPM. Keep driving it and it will do the same thing under normal driving conditions going up a hill.

So... here's what I've replaced from the back forward:
Fuel pump
Fuel filter
O2 sensor
Throttle Position Sensor (TPS)
Cam sensor
Distributor rotor
Distributor cap
Ignition coil pack
Spark plugs
Spark plug wires

And maybe more that I can't think of.
It's not a transmission problem because it will misfire in park/neutral when it's warm enough to misbehave.

I've read about the cat being bad or a bad crank sensor. I'd sure like to get this figured out, any advice will be greatly appreciated!
Thanks

Bustedback

Could be a clogged catalytic converter. Have a muffler shop do a back pressure test. You can also check it with a vacuum gauge hooked to the intake manifold. You should have between 15-18 hg at idle, if you start to see pressure instead of vacuum once the cat gets hot it means the cat is clogged. A temp gun is also helpful in determining if the cat is bad.

skykingjeep

What temp would you expect to see if the cat was bad?

Bustedback

The cat would be way hotter at the front than the back. You may also have a rotten egg smell coming from it.

dave1123

My wife's Dodge K-car blew the EGR valve right off the manifold because of a plugged converter. After I took it off, lung pressure didn't get even the slightest flow thru it.

skykingjeep

Problem solved!!!!

Crankshaft Position Sensor...

Not fun to replace but it solved my misfire problem completely. Engine runs better in general.

I hope this helps someone else out, it's been a very frustrating and expensive problem to chase.

Take care.