Mechanic changed the flexplate on my 2000 XJ last Thursday.
Truck has 137k miles and Jasper motor has 59k.
Saturday it started to throw misfire codes p0301 and po303 first.
Cleared them - the truck did not seem to be actually misfiring.
Two hours later codes for misfires cyl 1, 6 and random.
Cleared them and drove prob 50 miles on Sun - no codes.
Monday, today, heading to work got codes for misfires cyl 1,and 6 and random.
As this never happened before and now the truck has a new Jeep OEM flex plate, I can only assume that these things are related.... a buddy menti9oned something about the ECM having to "relearn" things related to the new flexplate.

Any input before I call the mechanic back??

Thanks.

Here's the cracked flexplate

 

UPDATE: I did some research and learned about what is referred to as "adaptive memory", i.e. that after changing parts, including the fly wheel I just did, the computer has to re-learn parameters using the new part. After having cleared probably 15-20 misfire codes post flywheel change, I performed what multiple sites and people said to do. That is re-set the adaptive memory. Remove the positive battery cable and touch it to a ground for 30 seconds or so. Put the cable back and turn key to ON position, turn headlights on briefly then off. Turn key off. Supposedly this drains the capacitors in the ECM with the lights being the final pull of current... this clears adaptive memory and the vehicle is back to factory pre-sets and re-learns with the new fly wheel in my case over the next 50 starting cycles. Since doing that 2 weeks back I have not had a misfire code at all when before it was not uncommon to have 4 a day. Is this smoke and mirrors? Works according to my experience here.

 

That method appears to be correct.
But have you ever experienced any actual misfires? Or is it just the codes coming up?

So many misfires from multiple/random cylinders, should be felt I'd reckon...

 

Thanks for the reply..... and no I have not felt what would certainly be present if multiple misfires. Previously once every 3-4 months or so it would start rough and stumble... throw a misfire code and I'd shut it down and it restarted fine. So I guess in this regard I would feel something similar if all the codes were actual misfires.

Just don't like to see the codes pop up... then I just have to clear em....
Works fine since the adaptive memory cleared though!!

 

Let us know if it returns. Might be worth looking into doing a tune-up (good maintenance anyway if not done recently), to have fresh parts and benchmark.

 

So far so good..... before I did this procedure I changed the plugs NGK's