Hmmn, got a bit of a head-scratcher here. 93 XJ6, 4.0 I6, 88,000 miles running like a champ on the way to the restaurant, turned into a 4 cylinder on way home.

When running I can pull the plug leads off cylinders 1 & 2 with no change in idle. Pulling 3,4,5, or 6 has a dramatic decrease in rpm & smoothness.

Took the fuel rail off tonight, good fuel pressure. Swapped the injectors from good cylinders to bad cylinders but trouble still with 1 & 2. Checked plug leads to 1 & 2 with timing light and they're firing. Put a spare plug in both leads and get a juicy spark. Plugs are wet so fuel is getting in there. No mechanical sounds from engine, in fact incredibly smooth.

Am I missing something? What on earth could shut down 1 & 2?

Oh and oil change was recently done and oil is still clean as a whistle, no signs of water in oil.

Help!

 

Just a shot in the dark, but try replugging/cleaning the multi-pin connector near the coil, sometimes they work loose! (mine did!)

 

It does sound like electrical. Maybe the plug wires have a break and are working intermittently? Good luck

 

Compression test to check for blown gasket between cylinders?????????????????

bob gauff

 

I'm riding the bike down to Tennessee for a long weekend. I don't want to do a compression test before I go and then be thinking about blown gaskets while on vacation. I'll take another look after I get back and post the results.

 

Don't worry it will still be there when you get back.
90% chance its a head gasket, take motorcarmans advice.

 

I waited a few weeks, hoping that if I ignore it that it might miraculously fix itself. Well it didn't so....
Cylinder # 6 = 180psi
Cylinder # 5 = 180psi
Cylinder # 4 = 180psi
Cylinder # 3 = 180psi
Cylinder # 2 = 0psi
Cylinder # 1 = 0psi

Strangely enough (or so it seems to me), no oil in the water or vice versa, so the gasket is gone just between cylinders 1 & 2. Once off idle, it runs lovely with no temperature issues and only a slight increase in fuel consumption.

So I'm on ebay now looking for a head gasket kit.

Out of interest, has anyone on here done a head gasket on a 1993 XJ4.0? Ay advice? It's only done 89k miles, but it did sit for a few years before I got it. Will the head likely need skimming or does the new gasket typically fix it proper?

Also, how long should it take me?

Any advice would be much appreciated.

Thanks!

 

I had the same problem on my 92 with cylinders 4 and 5. I pulled the head (the Haynes manual wasn't too bad - if you need it I can pm it to you) and took it to a local jag mechanic. They took the head apart, cleaned it, skimmed it (it had been scored enough that they felt it wouldn't seal well once it was back together) and replaced the guides when they put it together. I think the total came to around $700.

The only real problem I ran into related to the studs for the exhaust manifolds. Had to replace two of them. The head gasket kit has everything you need in it. There is a housing on the drivers side near the timing chain that does not have a gasket - I used RTV sealant on it and it has been fine since.

My father came out when the head was ready to come out. Was easier to have an extra set of hands to keep things out of the way and manage the timing chain while I pulled the head out. I got a new appreciation for how wide the car is when reaching over the fender to lift the head...

This was my head gasket

 

New gasket, even an aftermarket fits perfect. Two people is advisable for this job, as noted above. Many of us have done it, keep us posted if you plan on doing it yourself we can assist with questions during the process.

 

Who said Jaguars are gas guzzlers What an eco friendly car you have , it automatically deactivates some cylinders so that you emit lesser Co2
Al Gore would be pleased to see that

Excuse me OP , I mean no harm if you feel this message is off the line please use report button so that forum team can delete it

I wanna thank you who have helped you so far on this issue as well

 

Well, 4 months later and she's finally running again. Let me just say that anything that could have gone wrong, went wrong.

Pulled the head and sure enough, no gasket material between cylinders 1 & 2, totally burnt away. Both block and head looked OK, but I figure let's get it checked before I put it back. Took the head to a local engineering firm, who shall remain nameless at this point, to check for flatness. I get a call the next day saying they're going to skim it and that the exhaust valves looked a bit iffy. I figured that it would be a false economy to take shortcuts, so I had them replace all 24 valves and skim it for just shy of $600. Got the head back a week later and with my new gasket kit, set about the install. It was cold and I left some knuckle skin in various places, but I got everything back in place.

As soon as I cranked it, it was obvious that something was wrong. Sounded like the plugs were out. I did a compression test and had absolutely no compression in any cylinder. Now I'm second guessing myself. Did I miss anything? I was certain I had the valve timing right, but the doubts forced me to pay to have a mechanic drag her away to double-check everything. All my work proved to be right, so I became Alice in Wonderland's Queen of Hearts, "Off with her head"!

With the head off, I found that none of the inlet valves were fully closing. The valves and seats looked good, but with the cam lobe pointing to the sky, you could see a ring of light around all the inlet valves.

My visit to the, as yet unnamed, local engineering shop started out not as I expected. Instead of profusely apologizing, I was told that I should have set the valve lash myself. that was not part of a "head-job". I counter argued that I paid to have the head reworked in its entirety. I was again told that I should have set the lash when I installed the cams. Gotcha! They installed the cams. Point to me and they agreed to set the valve lash on all 24 valves that very afternoon.

Meanwhile, my attempts to purchase a head gasket ran into a whole different set of problems. Autoparts.titan1 on eBay had gaskets for $48 shipped, a great price. However despite having good quality gaskets and very quick shipping, these folks don't seem to be able to pack a head gasket. I have 2 brand new gaskets here all folded up nicely. Thanks USPS! Eventually, my local CARQUEST ordered one for me, but at $90.

So re-reworked head, new head gasket and I'm ready to go. Installation went well. A friend came up to help me and we knocked it out in no time. Incidentally, read the instructions before doing this job. I've done a few heads before and I figure just yank out the distributor and then set the timing when you put it back. Nope! Timing is adjusted by the ECU. You're supposed to mark it with paint when you take it out to insure it goes back exactly where it was. Thankfully the bolt had left a good clean mark and so it went back in as it should.

Upon start-up it was very apparent that one valve was tapping, quite loudly. Great job local engineering shop. I did an oil change which showcased the second problem. My buddy hadn't reinstalled the oil filler into the block. A quart of Valvoline's finest got poured down the side of the engine. I fixed that and finished the oil change. Now for the test drive.

She hadn't moved since early last October, so she complained a bit, but once the rust was scraped off the rotors, she drove fine. Right up to the point that the top hose blew off. OK so my buddy forgot to tighten the hose clamps. Hose clamps tightened, I set off to see how she goes. She was a bit lumpy and on came the 'check engine' light. Turned out to be a Fuel44 so I put in some fresh gas and gave her some right foot. Once cleared out the code has, so far, stayed away. She seems to drive nice again, except for that tapping.

I'll go visit the local engineering company next week and ask them if they'd be happy with the tapping valve after all I've been through and paid out. I don't hold out much hope and if they aren't prepared to do anything I'll spread their name like wildfire. I have a lot of petrol-head friends, word will get around. But with the cam needing to come out to do the valve, that means new head bolts and a couple of hours' work, I am not expecting them to fix it.

It'll be a bit disappointing, but at least she's back on the road again.