RudeXJ

So I feel like I'm nearing the end of my XJ initiation...well I hope so.

It all started with a tick that made me itch, so the head came off, lifters changed and gave it a whole general head job.

Everything back together and within a few miles developed a devilish exhaust leak...but against the head, almost like a warp. On closer inspection it turned out I had a 0630 head on a 2000 XJ and when I took the manifold off I realised the exhaust ports were way too small and the only option was a new ex manifold.

After a heap of back and forth, in and out of scrapyards, I found a second hand one in decent condition and after battling to put that bastard on myself, realised the exhaust downpipe didn't match up.

So after all that I had to have it towed to an exhaust shop anyway to match up the pipes.
Finally after all was hooked up and the moment had come, at long last, to hear that 4.0 purring perfectly, she started up and jumped straight to 4000RPM like a bat outa hell and wouldn't come down.

Ive checked all vacuum leaks, there are none. The manifold is on perfectly and everything is hooked up and have reset the ECU numerous times.
I did slip up and discovered I had forgotten that very important ground (fibre) cable that connects to the intake, thought that was my golden ticket, but didn't do anything (could this have been the cause....please say no)

I blocked up the IAC hole in the intake with a rag and the idle dropped down to 1500RPM so I'm pretty sure thats the issue. I took it out and cleaned it up...nothing. Is there any way to test it? Can anyone confirm this would be it?

I took a risk in the end put it in reverse, it wheelspun off the ramp and dropped idle down to 1700RPM, managed to drive it home, nearly died as I burned out the brakes and it wouldn't stop, literally a 4.0 without a leash!

The motor sounds amazing, I'm just stuck with this final issue...if anyone has any comments that would be greatly appreciated.
*I have read up on high idle threads, but couldn't find one that idles this high

OldTires

High chance of it being a leak at intake manifold gasket. What parts did you use and what gasket?

Any pics?

RudeXJ

I used the fiber gasket. It was missing one hole for the dowel pins the intake sits on so I had to make a hole - I then checked all the holes were indeed there.

Intake is sitting on those pins, pins are flush, not popping out.
Im 99% sure the intake is on properly, would a gasket leak really cause it to rev that high and if it's not on properly wouldn't I hear an exhaust leak too?

MonacaYankee

Should have bought this https://jeepexhaustadapter.com

cruiser54

The intake manifold is not seated against the head. Probably hung up on a locating pin.

RudeXJ

Can someone tell me how far the pins on the head protrude through the intake?
When I set it finally, the pins were just about flush with the intake, not popping through.

When I seated the intake I had to do it 3 times before I got it right...or at least I think I did.

97grand4.0

Man you go out on a thin limb when swapping manifolds around. Sorry to hear all that but I think Cruiser likely nailed it.
Hey at least the head doesn't have to come back off.

RudeXJ

Ok first things first, can someone tell me unequivocally wether the intake pins sit flush or wether they pop through when fitting against the head.

Secondly does an 00 intake fit together with a 0630 head exhaust manifold!!!??? I just assumed it would!!

Thirdly F&$#%ck

nujeepguy

i think there was a recent thread on the 00/630 mismatch in ports. look for it recent.

RudeXJ

I looked at that adaptor, besides the fact that I live in South Africa and shipping would take months, I really didn't want to restrict the flow. Having seen how much larger the ex ports are in the 0630 head, I thought it would be silly to try force it down the 00 ex header...really don't want to lose those horses.
When I drove it home from the exhaust shop, granted I nearly died, the motor had SIGNIFICANTLY more power than with previous setup.

RudeXJ

So you guys were right about it being an intake leak, but I was also right about fitting it correctly. Well we were all right, the f&@%¥ing gasket was wrong.

Check out the massive gap under intake port on C1



I saw on NAXJA that this head swap does work with old exhaust + 00 intake but has anyone experienced this issue with the gasket? I have a feeling that I just got a ****ty gasket. It did look way low when it was siting on the head.

kcdt58

I'd say you got a bad gasket. I have a 2000 intake manifold on an 0630 head with no issues. I used the fiber gasket as well.

RudeXJ

Ok well that's a relief, I'm going to have to find the person that made that gasket and punch him in the *****.

OldTires

It's probably a machine, but I feel your pain.

Glad you found it. Good luck doing the job all over again.

cruiser54

Are you using the gasket for the head you are using or the one for the manifolds you're using?