Anytime I have any questions or concerns regarding my Jaguar. I always consult this site. Not sure why I've never signed up. I've had this car for 3 years now. And last winter it started misfiring when it was cold out and the check engine light would start flashing. Did a tune up and replaced the breather hose. Thought it fixed it but it just got warmer out. I read a few posts regarding the vacuum lines and the IMT seals. I started it this morning and it was doing the same thing so I grabbed the plastic vacuum connector and the IMT seals. Didn't seem to do anything. I shut it off. And then immediately pulled it in garage and then it was just fine. Also last winter I learned that if you start revving it up before the gages come on and hold the rpms high for 30-60 seconds it fixing the problem and I'd be able to drive. If anyone has any thoughts I'd really appreciate it.
Thanks
Shyla

 

Have you checked the codes when the check engine light is flashing? Misfires are P030x. A P0300 means random misfires detected, P0301 means misfires detected on Cylinder 1, P0302 is cyl 2, etc. If you don't have a code reader you should borrow or buy one so you can check the codes as soon as you see the check engine light. It sounds like your codes might clear by the time you get to a shop when the engine is warm so if you have it in hand when you first start the car you can catch the codes. I bought a generic bluetooth code reader for about $12 and use a free app on my phone (Torque Lite) to read the generic OBD codes.

 

I have seen so many with this problem and have even had it myself.

Here is what I had to do.

I replaced the vacuum line from the brake booster to the manifold.

I changed the IMT seals

I removed the intake manifold and the bottom of the intake manifold (there are gaskets on both sides) Relatively easy to do, I replaced all of the gaskets there.

I was still having an issue though bank 1 lean I think I was getting.

The brakes became difficult at times to push (usually in the cool morning and briefly), then they became hard to push most all of the time.

I replaced the Brake booster (not as easy as the manifold gaskets)

This seemed to fix it for me.

Now I have to change a catalytic converter and fuel pump but I am not mentally prepared for that yet

I think the brake booster was the biggest problem for me, but The IMT O-Rings did need replacing, The intake manifold gaskets upper and lower did need replacing.

The hose from the booster to the manifold was likely ok.

 

I’ve had this same problem since I’ve owned the car for well over a year now and I’ve replaced every single gasket and seal that has anything to do with vacuum and still haven’t got it resolved. I’ve even disconnected the vac line going to the brake booster and plugged it at the manifold the night before and still had the same issue. Myself I don’t think it’s vacuum related because I never have lean problems when checking the fuel trims. As far as codes goes it’s usually 300 and a mixture of 301-306 but usually at least 4 of the 6 cylinders misfiring randomly. Like you and many others the only work around is to start it up and keep it rev’ed up to about 1500 to 1800 for about a minute or so and then switch it off and restart it and all is fine usually. One thing my car doesn’t do and maybe it’s what the problem is but I have to figure out what makes it do it but mine won’t automatically raise its own rpms when it’s cold out. Like start it and it’s running at say 12-1400 rpm then slowly drop as it warms up.