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Discussion Starter · #1 ·
All right guys I'm pretty dejected and am looking for help and ideas.

I did a quick tuneup on our 04 LJ. I flushed the radiator and refilled it with Zerex GO5. Changed the oil and filter with Mobil 10-30 high mileage, replaced the plugs with APP985, changed the air filter, and topped off the front and rear differentials.

Prior to the work everything was running smooth and strong, not so much now.

The Jeep now has a rough idle with a slight bounce in RPMs, acceleration from a stop is sluggish and it feels like the Jeep is lurching/surging with RPMs bouncing. Once I accelerate to around 50 mph it gets a rough shake. Coming off of the gas smoothes everything out.

I changed the new plugs back to the old ones and no improvements. I left the battery unhooked over night to reset the computer and no improvements.

I basically spent an entire day to turn a nice running LJ into something I'm afraid to drive over 40 mph. :(
 

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I've seen this happen when the battery was left on when removing coil rail or the rail was smashed up or soiled when pulling it out.

Check that the rail is clean, unharmed, and test it.

https://youtu.be/krFtcmViyBY

You're symptoms sound like the rail isnt firing properly. Assuming the plugs are gapped to spec, you used dielectric grease and didn't push any dirt into the cylinders.
 

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I changed my radiator fluid yesterday and did not realize I had to bleed the air out, never had to do that on any other truck I've ever owned. Anyway after I changed the fluid same problem it would barely start and almost choke out I read you have to bleed the air out, I took the radiator cap off and let it idle for about 20 minutes then it was fine.
 

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Discussion Starter · #4 ·
You're symptoms sound like the rail isnt firing properly. Assuming the plugs are gapped to spec, you used dielectric grease and didn't push any dirt into the cylinders.
Thanks. I'll check the rail today.

I checked all my gaps at .035 and put a dab of dielectric on the plugs. I had given the engine a general cleaning in the morning but didn't blow out each plug as shown in the video. Hopefully I didn't knock trash in.

I changed my radiator fluid yesterday and did not realize I had to bleed the air out, never had to do that on any other truck I've ever owned. Anyway after I changed the fluid same problem it would barely start and almost choke out I read you have to bleed the air out, I took the radiator cap off and let it idle for about 20 minutes then it was fine.
I tried to bleed the air out of the radiator for about the same time frame.
 

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You might have a D.O.A. plug. I have had a few over the years with boats, and cars.

Also check your plug wires. I had one go bad on me in my old 500SEL Benz after I changed e plugs. It was corroded inside and moving the cable broke the wire.
 

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Discussion Starter · #7 ·
Mystery solved!!!

It was a plug connection spring from the coil rail.



Put a new rail in and the Jeep is running great.
 

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You would think he would get a CEL with a code for a miss in the cylinder with no spark


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