I have taken compression readings and I am very confused.
90 VDP 91k

In order:

1 - 85
2 - 60
3 - 145
4 - 215
5 - 210
6 - 210

I need help, I am not sure what to do at this point.

 

could be a head gasket

 

Yes, it's looking that way. If it is blown between the cylinders that's why it doesn't show the obvious symptoms. This should be fun. I'll start on it tomorrow, if I could cam the job live here I would. But I will post pictures.

 

90 VDB Black
To say I am disappointed is an understatement. The black cat was my favorite of my 3. It was so quiet I never turned the stereo on, because it was purring. To have this happen has just left me broken hearted. I am debating whether to fix this or sell it. It is a big job. I'm not sure I will be able to tell anything by just removing the valve cover, which means the head needs to come off. Bottom line, it's a real bummer. I use to brag about this car daily! 92k on the Odometer, and virtually flawless on the inside and out. Heck the nitro cellulose on the wood in this car hasn't even cracked!

 

I'd have another test done. Just to be sure.

And have your coolant analyzed for hydrocarbons.

Sticky rings, sloppy valves could also affect your readings. If the valve isn't closing properly your comp test will be off.

I might have missed it, but is the car misbehaving?

 

Yes it is Richard. Perspective is the key to life, no doubt. The "misbehaving" was wonderful.
It had a fuel pump go, in which I replaced. 3 days after that felt funny, as if not running on all 6. I did the usual and it didn't correct it. I started digging deeper even pulling injectors and found 1 and 2 weren't firing in the cylinders. I then did a compression check. The readings are above. I tried that $60 head gasket stuff, just for grins and giggles to remedy a head gasket. It didn't work. She needs surgery. The "misbehaving" comment gave me incentive to fix it. So here I go.

 

Just pulled the head off mine this afternoon.
It was fun! Except for the bloody knuckles etc...
If you confirm that the hg is the problem have at it, especially if the rest of the car is in good shape.

 

@olivermc, I saw your pictures. I'm going to give it a try.

 

^Best of luck.

If you were nearer, I'd offer you a killer deal on my XJ40 and all you would need to do would be swap the engines.

+ none of that EGR gubbins to worry about.

Thinking, why don't you swap out the motor from one of the others and make a parts car?

 

I'm stuck in flux. I sold my white one, because my black vdp was running so good and I have the xjs v12 for summer. Then this happened. I drained all the fluids, there is no anti freeze in the oil. I tried the over the counter head gasket sealer, just to see if it changed how the car ran. It didn't do anything.
I took the valve cover off and started on the exhaust manifold. I then looked at the engine without the valve cover on, and stopped all work.
I do not think I have the mechanical aptitude to tackle taking that head off. And If I find out it's piston rings, I might as well have just gotten another motor.

I think I recall a post on here that someone had a similar issue, and it was a plugged up catalytic converter. So, I am going to put the fluids back in, disconnect the exhaust and start it. If by some miracle that is the issue I will be a happy man. If not I may sell it.

 

For those of you who said, "head gasket," you win!
There it is plain as day. All the things that can run through your mind about what the problem could be..etc. the only way too find out is to take that head off.

 

That's one that none of us wanted to win

You might want to replace the Oil Fill cap during your repairs, you would not want mice to get into the bottom end.

 

Good Idea!

 

As you can see, when you don't have a hoist you do what you have too.
Pics: New gasket on, putting the head back on.

Job is complete. It runs great. Gasket $58, beer for friends assistance $100

 

Good news, it always helps to have friends and beer!

 

Cool , good news . I honestly would prefer Jack Daniels lol