alr37115

I have a '99 XJ Sport with a 4.0... it starts, runs, drives, doesn't stall, smoke or overheat, starts with an idle of around 1000 RPM and a stop light idle of 750 RPM.but I have a CEL that brings up a P1398 code. The CKP sensor fuse is good. I was driving home from school, hit a bump and the CEL lit up. I checked the electrical connection and it and the wires are good. Should I pop the - battery terminal, unplug the sensor, plug it back in to start with? If that doesn't solve it... what's next?

CCKen

P1398-MIS-FIRE ADAPTIVE NUMERATOR AT LIMIT

When Monitored: Under closed throttle decel with A/C off, ECT above 75, and more than 50 seconds after engine start.

Set Condition: One of the CKP sensor target windows has more than 2.86% variance from the reference window.

Possible causes:
POSSIBLE CAUSES
DAMAGED TONE WHEEL/FLEX PLATE (CRANKSHAFT)
SENSOR CONNECTOR/WIRING
CKP SENSOR CONNECTOR/WIRING
CRANKSHAFT POSITION SENSOR
IMPROPERLY INSTALLED/LOOSE CRANKSHAFT POSITION SENSOR

Some steps you can take to troubleshoot:

Visually inspect the related wire harness connectors. Look for broken, bent, pushed out, or corroded terminals.

Visually inspect the related wiring harness. Look for any chafed, pierced, pinched, or partially broken wires.

Note: Make sure the Camshaft Position Sensor and/or the Crankshaft
Position Sensor is tight.


Disconnect and remove the crankshaft position sensor.
Inspect the tone wheel/flexplate slots for damage, foreign material, or excessive movement.

alr37115

I'll update after school tomorrow. It's about 15 miles one way so if it's gonna act up it will on the way to class. I did find a loose wire on my distributor cap and reseated it. After all the tranny problems were fixed, it gets up and moves when needed. Climbs these Middle Tennessee hills with no issues. Still can't seem to get rid of the s#itty driver problem we have here in TN.

alr37115

Drove to school with no problems, and no CEL. So far... so good. Will continue to observe and monitor. Thank you for your time.