bad idle and poor running

I am getting to my wits end with this jeep. I picked it up last year for $100 bucks from one of my buddies who couldn't figure it out either. The 4.0L was hydrolocked but then replaced with a long block. It idles really bad and shakes enough to loosen bolts on everthing attatched to the engine. I have gone through the Renix fuel injection manual a few times and every sensor tests out within spec. The TPS is adjusted correctly, I replaced all of the injectors with 19lb fords, and all ground wires are in good condition and I upgraded all battery cables and added additional grounds. Wires, cap, rotor and plugs are all new high quality parts. It also gets terrible gas mileage and runs really rich at times. I need this rig to be reliable since I have my other jeep undergoing a new round of mods. Am I missing something really obvious? Does anybody have suggestions? The nearest dealership that can scan the computer is 3 hours away and I don't want to drive the thing that far.
Some possibly relevant specs:
89 limited
4.0L
AW4
19lb injectors
cat back exhaust
CAI

CW how about you check timing. sounds like that's the problem if the engine was replaced.

jeepcomj said:

CW how about you check timing. sounds like that's the problem if the engine was replaced.

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Sounds like you may also have a bad O2 sensor as well, but check that distributor first for sure.

I pulled the distributor and put it back in myself to make sure it was done right. It's a factory cam so I hadn't even thought about indexing the distributor. I guess I'll try that. The O2 sensor is new so I know thats not it. Sometimes it's hard to resist the urge to just pull the stroker out of my wheeler.

Check obvious stuff like an arcing spark plug wire, chaffed wire(s) from all sensors, ECU, connectors, etc.

If all that falls then you might try swapping the computer. Get one from someone parting out their Jeep or if you know someone with a spare.

Are you sure you have the dist. index Right? That can be a real bugger some times!

TDC compression stroke, dist. pinned so that it is aligned and makes the dist rotor, and housing as one piece.

usually it requires a big flat bladed screw driver to turn the oil pump drive, so that when the dist lands flush, it's align with the retaining bolt hole.

Flash.

Bringing this back up. I pulled the timing cover and replaced the chain and sprockets and then indexed the disributor following the tsb instructions. I also replaced the O2 sensor and cleaned, painted, and checked every part I could find under the hood. I replaced any wiring that looked even somewhat questionable too. It runs smoother (but not smooth) and gas mileage improved to around 13 mpg on a long highway trip, but it is still knowwhere close to acceptable. Any other suggestions? I am running out of ideas on this thing. I think I'll pull the manifolds when I get another few days off and replace the gasket just to make sure I don't have any leaks causing this.

Computer, coil, arcing plug wires, EGR valve, fuel pressure regulator?

The coil tests good, plug wires are all new, the EGR system was gone when I got the jeep but I made sure all of the vaccume lines and everything were plugged (I've done this on two other jeeps with no ill effects). The FPR is was swaped for a known good one off of my wheeler. I would hate to just throw an ecm at this thing but I'm starting to think I should try it with a junkyard unit. This is irritating, I'm an ASE certified parts guy and I can't find the problem with this flippin thing.

Even though I've gone through numerous brands of wires, including OEM regular and OEM high performance sets, for some reason the plug wires on my XJ arc bad. Take a look at night where there's no light just to make sure your wires aren't arcing.

Sometimes you can get a computer for cheap at one of the yards, so certainly worth the effort. That's what I plan to do with my POS.

CW said:

This is irritating, I'm an ASE certified parts guy and I can't find the problem with this flippin thing.

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I have noticed that gremlins do not descriminate, they haunt even the best of us! Most Of what I am listing you already know, but sometimes it helps to back to the beging and retest even new items, so

Have you checked some things to make sure you did not get a bum engine, like checking the operation with a vacuum gauge? Is the distributor new? Did it come with the block.

New rotors can be defective!

I have found that a bad O2 sensor can be diagnoised (as far as rough running goes) by disconnecting it as a test, I doubt that will be your problem since you have a new one, but a trace of silicone from antifreeze or antisieze or silicone lube on the outside of a new can kill an O2 sensor (I am told my Bosch).

This is going to sound stupid, but make sure the TPS and O2 sensor connectors are attached backwards. I have an old wiring harness and I discovered the hard way (drove me nuts for weeks) that they could be attached backwards on the older renix harness once some of the plastic clip stuff breaks off. I made a post on this last year. It still ran with both attached backwards, but the gas mileage tanked and it ran rough.

My runs nice and smoth now and is a stable DD after two years and replacing everything but hthe engine, tranny and ECU and I am still getting about 11 mpg local and 13 to 15 mpg on a full tank with 80 plus percent highway driving. I got a 15 mpg rate once for the first time about 10 weeks ago, but last mostly highway tank full was only 13 mpg. I did just replace the mufler on mine (but you have a new exaust system as I recall reading) anyway I am changing my Cat next and hoping to see at least 16 to 18 highway by then, if not I am in the same boat as you running out of things to fix to get the mileage where it should be.

Have you checked/changed the CPS? Thats what is keeping mine off the roads right now, sounds similar. I have a 1988 limited. good luck