Rough idle/accel. No idea where to start...

[jprintz9]

This is for my 98 3.0 4x4 with 115,000 miles.

Driving home from work this morning I hard a loud clanking sound from the engine compartment while getting up to speed. The noise stopped and everything seemed ok. Then I noticed that in order to stay above 65 mph the truck needed to maintain 3k rpm or more. It would not shift. The acceleration became rough, shaking the truck rough. When I stopped at the light, it idled rough but did not cut out. It shifts fine at low speeds in town, just rough around the 50 mph mark.
I changed the plug and wires out about 4 months ago, oil level is good, and I have no CEL/no codes.
I've done all my own repairs on this truck but I'm not sure what direction to head on this one with no CEL. Could it be the distributor? Maybe a shotty injector?

Any feedback is much appreciated guys and gals.

Thanks!

[KnobbyTires]

I went through a similar self-destruction at 98K miles on my 2000 Ranger, 4.0L V-6. I took it in to a shop. They checked compression, charged me for one warped head and one cracked head, then gave it back in similar condition. Looking back, I should never have let them do any work without doing a "leak-down" test of each cylynder. The rings were overheated and would never go back to a normal set. I had lunched the engine, and they had eaten lunch with the money I spent.
- Replace the fuel filter
- Check for coil firing, spark at each cylinder
- Timing belt jumped teeth
- Battery with loose cells, shorting battery positive, any number of things
- Let them read the codes and go from there... good luck

[jprintz9]

I forgot I posted this!
It ended up being a few problems. The main reason was I some how managed to bend an exhaust valve which cut compression to the #3 cyl.
To make a long story short we ended up tearing off the heads, replacing them, cleaned up the valves, and put in new gaskets on the whole thing. it ended up being about 1k in parts, and it was a complete nightmare. Good news is that it's running like a champ again. 119k and running strong. The only issue I'm running into now is the "Off-Road" Suspension. 800 bucks in parts and you have to take out break/gas lines to get the upper ball joint assembly. Sad to say it but I'll be dumping the old danger ranger in a few months here.
Thanks for the reply!