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Unread 08-08-2013, 03:34 PM   #1
gunner_woody
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Fustrated and need help!

To start, my son has a 2000 XJ 4.0 with 3"lift and cut fenders. He bought it used and yes, it had the dreaded head that was cracked, so being a jeep lover, I replaced the head with a 0630 casting out of a junk yard 97 ZJ. The XJ ran rough and kept having a P0302 (misfire cylinder 2). I changed the plugs, coil rail and verified the timing. This did not work, so I did a cylinder pressure test, all were within tolerances but #2 was the lowest pressure so I changed the rings in all cylinders. Still idled bad and threw the P0302 code again. So I bought a remanufactured head from NC heads and just replaced it (again) no code (yet) but idles like crap almost like it is missing again. I tested the coil rail again with a Mac coil tested and the fuel injectors with a Mac fuel injector tester.

So to summarize, new head, new cylinder rings, new plugs, good coil rail, good injectors, timing is correct, no loose wiring, no cracked or leaking vacuum lines and no codes... Why is this idling rough?

I am at my wits end and out of ideas, can anyone help?

Woody

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Unread 08-08-2013, 05:32 PM   #2
gunner_woody
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Hello?
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Unread 08-08-2013, 06:58 PM   #3
wgirvine
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Hello?
Patience, grasshopper. Patience...
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Unread 08-08-2013, 07:01 PM   #4
wgirvine
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I am curious though...

Doesn't the 2000 4.0L have the coil rail that bolts to the head? How did you bolt the rail to the '97 ZJ head?

One more thing... I realize this will probably fall on deaf ears, but if your title was more descriptive of the actual problem, people might be more inclined to read your post. "Frustrated and need help" tells me nothing. "Misfire After Head Replacement" at least gives me an idea what your problem might be.
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Unread 08-08-2013, 07:29 PM   #5
gunner_woody
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Quote:
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I am curious though...

Doesn't the 2000 4.0L have the coil rail that bolts to the head? How did you bolt the rail to the '97 ZJ head?

One more thing... I realize this will probably fall on deaf ears, but if your title was more descriptive of the actual problem, people might be more inclined to read your post. "Frustrated and need help" tells me nothing. "Misfire After Head Replacement" at least gives me an idea what your problem might be.
Yeah, no deaf ears here on the title, I was about ready to kiss the XJ with my 12ga working end, so I was just venting...

The 0630 casting is not made for coil rails but I fabbed up some brackets that indexed off the valve cover and held the rail on.
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Unread 08-08-2013, 10:43 PM   #6
Holder350
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I would run a ground wire to the coil rail. Your brackets may not be making a good connection to the rail.

That's my only idea at the moment

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Unread 08-08-2013, 11:02 PM   #7
wgirvine
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I was thinking the same thing as Holder about a ground wire. You would think that a missing ground would affect all the cylinders but hey, you never know...

Make sure it's got a good ground.
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Unread 08-09-2013, 05:43 AM   #8
gunner_woody
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I would run a ground wire to the coil rail. Your brackets may not be making a good connection to the rail.

That's my only idea at the moment

Sent from my phone
I get what you are saying, what I am unsure of is where to attach the ground to. The coil rail is made from an ABS like substance, where the original mounting bolts went through the rail there is no metal, so how can I properly ground this? And would a loose or no ground cause a code, since I have no codes?
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Unread 08-09-2013, 05:50 AM   #9
Holder350
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Look at the underside and see if there is a metal boss where the coil rail mounted down to the head.

I'm not saying that I know that's your problem, but its just an idea and I should think it would be worth a shot.

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Unread 08-09-2013, 06:10 AM   #10
gunner_woody
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Any shot is more than what I have right now, I will look at that today.
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Unread 08-09-2013, 07:58 AM   #11
CCKen
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Quote:
Originally Posted by gunner_woody View Post
Any shot is more than what I have right now, I will look at that today.
According to the wiring diagrams, the coil rail is not grounded through its body.

Just curious: What gasket did you use to match up the 0331 head exhaust/intake pattern to the 0630 head pattern?
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Unread 08-09-2013, 08:54 AM   #12
gunner_woody
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Originally Posted by CCKen View Post
According to the wiring diagrams, the coil rail is not grounded through its body.

Just curious: What gasket did you use to match up the 0331 head exhaust/intake pattern to the 0630 head pattern?
As a temporary measure I used the gasket for th original 0331 head. The air intakes match up, it is the exaust manifold that is only slightly diffrent. As I said this is temporary and I will match the exaust manifold to the 0630 head when I redo the exaust system
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Unread 08-09-2013, 09:47 AM   #13
CCKen
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Quote:
Originally Posted by gunner_woody View Post
To start, my son has a 2000 XJ 4.0 with 3"lift and cut fenders. He bought it used and yes, it had the dreaded head that was cracked, so being a jeep lover, I replaced the head with a 0630 casting out of a junk yard 97 ZJ. The XJ ran rough and kept having a P0302 (misfire cylinder 2). I changed the plugs, coil rail and verified the timing. This did not work, so I did a cylinder pressure test, all were within tolerances but #2 was the lowest pressure so I changed the rings in all cylinders. Still idled bad and threw the P0302 code again. So I bought a remanufactured head from NC heads and just replaced it (again) no code (yet) but idles like crap almost like it is missing again. I tested the coil rail again with a Mac coil tested and the fuel injectors with a Mac fuel injector tester.

So to summarize, new head, new cylinder rings, new plugs, good coil rail, good injectors, timing is correct, no loose wiring, no cracked or leaking vacuum lines and no codes... Why is this idling rough?

I am at my wits end and out of ideas, can anyone help?

Woody
Before the head change, was the engine runnng rough like it is now?

I would expect the new head to have new valve springs. Did it?

I think the only thing that remained the same with the head juggling was the Rockers, pivots, bridges and push rods. Correct me if I'm wrong.

You may want to double check the rockers and pivots on #2 for excessive wear, the push rods on #2, and verify that the bridges aren't twisted. As a general practice, before torquing down the rocker capscrews, each respective cylinder should be at TDC compression to take the load off the bridges. Torqued, in steps, to 21 ft. lbs.

Even though you are not getting a fuel injector DTC, the injector for #2 may be clogged, or otherwise defective. Try swapping #2 injector with #3 and see if the problem follows. Ensure these injectors have new o-rings fitted before reinstalling.
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Unread 08-09-2013, 12:22 PM   #14
Holder350
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Might want to check for a flat cam lobe on #2 also

Sent from my phone
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95' XJ Country - Stock Skids - D30/D35 Limited Slip - 3" Lift - 31x10.50R15 - 4.0 HO - AX15 - NP231

98' XJ Classic - D30/C8.25 - 4.5" RC Lift - 33x12.50R15 - 4.0 HO - AW4 - NP231
Quote:
Originally Posted by Azzy View Post
You can tell the character of a person in how they treat someone who can do nothing for them.
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Unread 08-09-2013, 02:02 PM   #15
gunner_woody
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ok new development, while I was at work my son drove it to an interview. While he was driving it shook badly would not go over 55mph and now has codes P0300 (random misfire) P0302 (misfire cylinder #2) and P0305 (misfire cylinder #5). Back to the drawing board!
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