I was gifted my dads old XJ about a year ago and I’ve replaced almost every major component in an attempt to make it a reliable road trip car, he said this has been happening since he got the car and nothings ever changed it, but the problem I’m having is after driving the car at 70-80 MPH for an extended time let’s say 25-30 mins I’ll begin to get a bucking/lurching with the car then it will start with the flashing CEL and throw me a bunch of codes and start missing, but the second you shut it off and restart it it will run fine again like nothing happened until you start pushing the car again at high RPMs or higher speeds , it also won’t let me clear the codes even when the car is running fine again

Codes Given:

PO353

300

303

304

442

455

Mind you this has happened many times in the past, I’ve replaced the ignition coil, spark plugs, IAC TPS MAF, Cam sensor and crank sensor with all mopar and NTK parts, also brand new cats and o2 sensors, fairly new fuel injectors, brand new fuel pump, I’m stumped I’ve put lots of money into my XJ and would like to be able to use it for anything faster than 60-65 mph on the Highway, the only thing I could think of is the PCM, car has 238k miles on it, any help is greatly appreciated

 

Have you looked up the codes?

What year is it? A prior post of yours suggests it a 2000.

P0353 - Ignition Coil 3 Circuit

P0300 - Misfire random cylinders

P0303 - Misfire #3 cylinder

P0304 - Misfire Cylinder #4

P0442 - Evap leak - small

P0455 - Evap leak - large

 

it’s a 2000 sport

I’ve known about the Evap codes for awhile, but I keep getting the same problem no matter how many times I swap a different ignition coil, my dad said he tried to fix it but he never could figure it out and eventually it would happen again, I’ve heard that it could either be a speed sensor or PCM I’m not sure though

 

So there is a solenoid in the evaporative control system, that if it plays up will cause the exact symptoms you describe, hard to track down, as most dont believe this could be the cause

(Ignoring misfire codes) I though the 2000 model has a wasted spark design with multiple coils ?

 

interesting, I’ll hop on rock auto and see if it resolves it, nope i have a singular coil pack/ ignition coil,

 

ok changed solenoid, repaired a cracked fuel vent hose in the rear and new gas cap then disconnected the battery and reconnected as I couldn’t clear the codes, drove the car about 150 miles in the past 2-3 days and CEL hasn’t came back on, I still have my problem unfortunately, after extended high speed or use it will start to buck on the highway at about 70-75 MPH or so then I’ll get a occasional slight miss that after about a half hour or so it will get a little worse and run a little rougher also feel like it may lose a bit of it’s “peppyness” only two things I could think of it possibly a malfunctioning computer or Speed sensor, kinda at a loss here

a list of all that’s been replaced,
Cam Sensor NTK
crank sensor Mopar
IAC Standard motor products
Maf NTK
TPS NTK
O2 Sensors NTK
Both Catalytics ( Cali emission car )
Emission Solenoid Standard Motor Products
Ignition coil NTK
Spark Plugs NTK
Delphi Fuel Pump
Filler and vent hoses
Gas cap
fuel emission vent line

 

Its a tricky one, are you saying you could not clear any codes with an OBD2 reader ?

 

Yeow! That's a lot of parts. (Double Yeow for the CARB Cat!!)

Does your OBD reader show live data? Does it record it?

Did you replace the spark plugs wires as well?

 

No plug wires on a 2000-2001. How about checking and cleaning ALL the grounds.

 

displaying my ignorance, but the OP says he has a single coil, but I thought 2000-2001 had a coil rail, coil over plug arrangement ?

 

That's what I thought too. The P0353 would suggest that. He said "singular" but perhaps he meant it's one unit, not individual coils like on other vehicles.

 

3 and 4 share a coil in the coil rail, so that's a good place to start.

 

It does have a coil rail over all 6. It is a way spark system so it is sharing the 3 coils over the 6 cylinders and yes the center coil on the rail handles 3&4. You can use a spark tester to see if 3&4 are firing. Pretty quick and easy way to check if it is good. Spark testers are pretty cheap too. You do unfortunately have to replace the whole rail even if just one coil is bad. RIPP does make a coil pack with wires that I hear is nice but still this would be one unit. I think MSD also makes a higher output coil rail. I think the stock style from the parts store is 80 bucks give or take. I haven't used higher output coils before but I have a friend that put one on his jk and thought it ran better.