Ok so about 2 weeks ago my XJ was running beautifully. It was running better than it ever has since I got it. I just replaced my cracked exhaust manifold, and replaced my cap in rotor and spark plug wires.

Well about 2 weeks ago leaving work I raced my xj onto the freeway. Didn't go above 65mph or over 5k rpm. It drove fine all the way until I hit the off ramp. When I came to a stop my idle was horrible. So I went home and parked it. I also noticed the exhaust sounded like it was leaking by the muffler. Next day it starts and I go to take it to work I get down the street and it's idleing horrible. Look at my dash and I have a CEL. So I drive it to Autozone to check the codes. Still idling horrible but seems to drive well. So I checked and I have codes P0300 and P0301. Random Multiple Miss and Cyl 1 Miss.

So I got a hold of my own scanner so I could test things. I tried unplugging Fuel Injector one to see if it would change and it did started running worse. However now I am getting code P0201 Injector Circuit Cyl 1 Now even after clearing codes. That wasn't there before but now wont go away. Also getting pending code P0302 for Cyl 2 Missfire.

I hooked up an inline tester to the spark plug on cyl 1. It's getting spark. I did the screwdriver test on the injector and its firing. Not sure what else to try.

What I do know. I used seafoam in the tank a day before this happened. Maybe something clogged the injector? Last August I did replace my CPS with an Autozone one. Yea I know its AZ totally could be the sensor. However how would driving fast ruin the sensor? I also have a flex plate knock. I wonder if I cracked it worse/more? I took off the inspection over however it looks fine. Also my cat converter has split it seams and is leaking exhaust out the side. This didn't happened until it started idling rough.

So yea kinda lost right now. I suck at diagnosing so this is driving me crazy. Anything you guys can think of to test or try? Thanks

Ok so I tested Ohms on the Fuel Injector, its the same as the rest of them 15ohms. So I tested my CPS and it was showing 18ohms. Now its showing infinit but jumping to 18ohms randomly. So maybe my CPS is to blame? I cleared my codes and now just P0300 and P0301.

 

Do a compression check on #1 cylinder, and a compression loss check on that cylinder. Doing the compression loss check requires a soruce of compressed air, applied to the cylinder (80-90 psi).

With air applied, listen for air escaping the TB (intake valve problem), air escaping the tail pipe (exhaust valve problem), air escaping the oil fiiller port on the valve cover (rings).

Normally the injector resistance is 12 Ohms, at room temp.

 

Ok well I have somewhere to start checking. My Injectors when I tested them were nice and warm from the sun and running. So I guess that would explain the higher reading.

Also one other thing. A couple of times the CEL has turned off and I was reading no codes. The two codes end up coming back, it's just weird it would go away for a bit.

 

The PCM works its wonders in mysterious ways.