idle's great. wont rev 15-2000 rpm

So I just rebuilt the 4.0 in my 97 xj. went to start it up for the break in, and it ran great. until it went to closed loop. now it idles like a dream but any gas I give it makes it stutter, plus wont go past 1500 rpms. its also running super rich. I figured o2 or position sensor but no codes are being thrown. this is puzzling me, any help would be great.

Timing is correct ?

O2 sensors would be the likely place to start. Test sensor function, inspect sensor wire plug, test sensor wire harness, test sensor heater fuse.

Test Throttle Position Sensor.

I just thought about the timing after I closed up shop. I look at that tomorow.

The last time my O2 sensor was going bad on my 96 it didn't throw a code until the O2 sensor completely died. There was a period of weeks where I knew something was wrong, it progressively got worse and I had no code until it was completely dead.

After a couple/few minutes of warm up, it would chug, buck and miss anytime I tried to give it any throttle. I first swapped out the TPS, cleaned my MAP orifice and throttle body, no improvement. Swapped out the O2 sensor and all was right. Next step was going to be testing TPS, MAP and O2 wiring, glad it didn't get that far. Tearing into the harnesses is a last resort for me, I'm always afraid I'll do more harm than good, those connectors get brittle with age.

Make sure your O2 wiring is well away from the exhaust. I added a few cable ties, just to make sure. I also made sure the innards of my connectors were clean and oil free.

I checked the wires. I after the timing I was going to try a new o2 sensor.

i know its been a while. but finally got around to messing with ole green. finally got a code to throw. no crank correlation at pcm. so naturally I replaced the tps. that didn't fix it. so I think pcm. but wouldn't it just not run if the pcm was bad??

Exactly what Check Engine Light trouble codes (by the numbers) are or were present ?

Engine code p0320
Transmission code p1694.
I reset the p1694 and hasn't come back.

After messing with all the wires it is possible that a wire splice has failed, or that some wire insulation is chafed or damaged. A faulty sensor wire circuit or wire connector looks the same as a faulty sensor to the PCM.


P0320 - Crankshaft Position Sensor Malfunction

Possible causes

- Faulty Camshaft Pickup Sensor
- Faulty Crankshaft Position Sensor
- Ignition/Distributor engine speed sensor harness is open or shorted
- Ignition/Distributor engine speed sensor circuit poor electrical connection
- Low battery charge

When is the code detected?

The P0320 code is triggered when the Engine Control Module (ECM) detect an improper signal from the crankshaft position sensor.

Possible symptoms

- Check Engine Light ON
- Lack/Loss of Power
- The engine may be harder to start
- The engine may stumble or stall

I had this exact symptom. It turned out to be the CPS,