You guys have been awesome, thanks for all the help with this. So we're all up to speed with this:

-99 XJ, 174k, AW-4, NP-242, OEM spec everything.

-New everything: TPS, IAC, o2, ECM, Refreshed battery leads/ground, refreshed PDC harness and checked fuses/swapped relays, all grounds- oil dipstick, firewall to back of head (braided line), the one on the driver side wheel arch by ECM.

After discovering/replacing the broken dizzy cap it fired right up. Hadn't done this in a week and a half. No more rough idle, hesitation, no high end rpm's. Then, after 4 miles it threw the o2 sensor high circuit code.
Then I drove it more and I got this:

 

To be specific, the IAC was new a month ago and the IAC code was just today, never happened in the 5 years I've owned it. I unfortunately don't have a MM so I'm useless there.

 

Just refreshed it. I've been all over the wiring harnesses found a weak/exposed area and taped it up. This was a while ago. Worth more effort in actually fixing it I'm sure.

 

Aren't they fixed to motor housing?

 

So earlier it was running fine. Did you notice anything when it started throwing codes?

 

Yes, there are studs on the housing that pass through firewall. And to clarify, it was a 1991 XJ that I had taken apart to get to the heater core.

 

Before o2 high code (first code) it was hesitating while in 4th and trying to accelerate. The hesitation quickly turned to the rough idle with one stall. It hesitated under any throttle and would bog out if given too much throttle. Then after more driving I got all the misfire codes.

 

Figured it should be.

I've read here where replacing the heater cores in these XJ's is a chore. I tell you though I don't see how it could be any more than replacing the one in our '96 Blazer LS. Two man job.

 

Why does my low washer light come on when it is 3/4 full? I think that is a common thing just didn't want to search for a logical explanation.

 

Common thing. Come to think of it I haven't seen my light in a while.

 

Another random thought as I'm reading up on gauge accuracy and needing to confirm it, does anyone have a custom dash / gauge cluster?

 

No but I'm seriously considering installing an oil pressure gauge,trans temp gauge,and coolant temp gauge.

 

Things went downhill quick that's for sure. I'll do some searching to see what I can come up with. I'm figureing others will reply.

 

Mine does the same thing It's the ultimate idiot light. I unplugged the sensor on bottle.

 

anyone know if the overhead console from a zj will work in an xj?