Misfires, jumps and feels like maybe sensors?

[MobilJoe1]

So... I have a 1991 jeep Comanche 4.0HO AX-15. It idles excellent. I added ponies in neutral to 2500rpm and it runs excellent. Now I am in 2 gear (same as 3 gear) down the road and it jumps, misfires and about to die at around 2000rpms. When I added more go fast peddle to 3000rpms, it runs excellent. I have replaced thus far: cap and rotor, wires and new champions spark plugs. I have disconnected upstream O2 sensor and drove also and it is the same. I have gone through posts after posts on this site and plenty of youtube info and I got no where. Oh and also it is not my daily driver, I only go on off road trips with it. It sits for 3 week more or less depending on time. It has brand new engine (stock) and trans with about 30,000 grand on it. I am very much mechanically inclined. Kindly help of you can. Thank you, Joe. 

[224ftlb]

Could be as simple as cleaning grounds. Could be stale/watery gas. Could be a loose flywheel. Could be cam sensor. Could be timing chain. Could be cps. 

Get an old snap-on or otc scanner that reads live data so you can check it out as it's happening because I don't think these store codes and if they do they're pretty general. 

[MobilJoe1]

12 hours ago, 224ftlb said:

Could be as simple as cleaning grounds. Could be stale/watery gas. Could be a loose flywheel. Could be cam sensor. Could be timing chain. Could be cps. 

Get an old snap-on or otc scanner that reads live data so you can check it out as it's happening because I don't think these store codes and if they do they're pretty general. 

Thank you for the input, thus far, I changed 02 sensor, tps and tomorrow the famous crank sensor. I believe it is the crank but who knows. 

[Pete M]

be sure to test the sensors before replacing them

[gogmorgo]

Have you checked for trouble codes? The CEL only comes on when the fault is present, but codes are stored for at least a little while and can be accessed by cycling the key a few times. 

I would put money on it not being the crank sensor. Crank sensor is an all or nothing deal, not just a little stumble.

[MobilJoe1]

Ok. I have read all off your posts thus far and I have changed thus far: cap, rotor, new wires, new champ spark plugs, O2 sensor, crank sensor, throttle pos sensor, coolant sensor and went through thoroughly to make sure there is not vacuum lines leak. I have cycled 3 times ignition for getting some codes but nothing. It is still starting up and running just fine in idle but when I accelerate in first, dies. Back to the drawing board. 

[Ωhm]

19 minutes ago, MobilJoe1 said:

I have cycled 3 times ignition for getting some codes but nothing.

 

Shouldn't the vehicle show at least a PASS (12) code?

 

22 minutes ago, MobilJoe1 said:

It is still starting up and running just fine in idle but when I accelerate in first, dies.

 

Could vehicle be in "limp in" mode?

[MobilJoe1]

2 hours ago, Ωhm said:

 

Shouldn't the vehicle show at least a PASS (12) code?

 

 

Could vehicle be in "limp in" mode?

Yes, I would imagine so. Limp mode, yes. And yes it gave me code 12. 

 

[Ωhm]

With code 12 you're not in "limp in" mode. Problem could be 'Non-Monitored' circuits or systems. Fuel Systems/Issues are on the top of that list for things to check.

[gogmorgo]

When you changed distributor cap and rotor, did you check to see if there’s play in the distributor shaft?

I’ve been dealing with a similar stumble on my ZJ. Nothing under heavier throttle but gentle acceleration or parking lot speeds and it would cut out, super obnoxious with the five-speed. No codes, and looking at sensor data with my snap-on brick hasn’t revealed anything. The things I’ve done to it that have made a big difference though have been tightening the intake/exhaust manifold bolts which got me two months, then changing the intake/exhaust manifold gasket, which “solved” it for about six months and then about a year ago I changed out the distributor because the shaft had enough play it was leaking oil into the housing, and it’s been behaving ever since.

Changing any of the sensors out with known good ones never changed anything. The only measurable symptom I ever got was little up or down ticks in fuel pressure just before and after it would stumble. The sync sensor, sometimes called camshaft position sensor, lives in the distributor and is what determines injector timing. I suspect the wobble in the distributor shaft was screwing with the sensor readings but that’s just a guess. 
If you do go for a new distributor I’d recommend getting the ‘95 style. It’s got the sync sensor just under the rotor so you don’t need to pull and disassemble the whole thing if you ever need to change it. But I would try to swap in a known good one if you have access, no sense throwing out money on new parts you don’t know will fix the issue.