97 Dakota 3.9 automatic 4X4 with 250038 miles. 235/75R15 LT tires.bought with 198K on it and only history I know of is the trans was replaced. full tune up at 215k. I keep the oil changed lose 1/2-1 quart in 5k miles, injector cleaner 1/2 dozen times a year.not a power house to begin with but she suddenly became a dog. the cat converted had gone to rattling, and on the way home pulling our 1500 lb pop up she could hardly maintain 65 mph on flat ground, rough idle but no smoking or overheating. 1 code came up, bank one lean.cat pulled (its shot)and run with open exaust and theres no upper end power.put in a test pipe and she still falls short....almost like the throttle body is not opening all the way up...(it is) the idle is alittle rough no smoke and will spin the tires aliitle on take off but just flat on the upper end. Will be doing a compression check this afternoon. I know some can be from the lack of the converter, also wonder about the timing chain causing issues....no noise that I hear.any other things to look for?
Thanks Darrin

 

If you're running no cat on one side, it'll give the computer fits. Can't say for sure, but it might have gone into limp mode maybe? Not sure if the pre-00's have 2 O2 sensors or not, but if it gets the same reading from the pre-cat and post-cat, the computer's gonna tune things down. Not having that backpressure probably isnt helping either, maybe? (granted some users here are cat-delete)

 

1) 125/140
2) 120/140
3) 130/145
4) 100/120
5) 95/110
6) 110/120
dry /wet reading, warm and throttle open
It has only single exuast and an o2 sensor post converter
Darrin

 

far as I'm concerned, not too bad for a quarter million miles. Our racecar only has 160 or so and we just built it with 14:1 compression. So I say it's right in line. (Camshaft makes the big difference)

 

Cam does make a differance....that why I wonder about a stretched chain and retarded cam timing as part of the problem.....Darrin

 

At that mileage, timing chain has to be stretched some. Worn cam lobes also come to mind, but looking at your compression it may not be a neccesity YET. However at 250K a rebuild might be a wise economical decision. In the meantime, get that cat replaced and get 2 new O2 sensors. You will pull your hair out battling 2, 3 or 4 issues while trying to diagnose it.

As far as the idle being a little rough, well, it's a 3.9. You're never going to get rid of that.

 

Plugs look good. lt tan/white with very little carbon....new plug wires....broke 5 of 6 comming off. idles better but still slack. converter on order, and well see how that goes.

 

well new converter and muffler, and once it got warm it started acting up and kicked 2 codes 0132 o2 sensor hi
and 0171 bank 1 lean...
seems the more I fix the worse it gets.
any ideas where to look next?
TIA