Originally Posted by kr98664

https://www.youtube.com/watch?v=1IPPn9t6dyE


In the kindest, gentlest manner possible, I'd have more confidence if you had successfully rebuilt this type of engine 10 times, and those 10 vehicles are out driving around with no issues. Unfortunately, all we have at the moment is you've torn down and reassembled this particular example 10 times. For all we know, there's some unforeseen issue causing a problem, and this same oversight has been repeated 10 times.

I'm not very familiar with this engine, but I can offer an example from a different type of engine. On older engines with conventional timing marks on the crankshaft pulley/harmonic balancer, it's possible for the inner rubber core to slip. This causes the timing marks to be inaccurate relative to the crankshaft, but this is not obvious at first. On other forums I frequent, I've seen this trip up many people, regardless of their experience level.

The low compression across all cylinders makes me wonder. There are many variables that can skew a compression test to read low. For example, a low battery or a tired starter reduces the cranking speed, which can give misleadingly low numbers. As an aside, I've been taught never to condemn an engine solely on a cranking compression test, but to run a cylinder leakdown test for confirmation. The cranking compression test is relatively quick to do, and if it passes, you're good there. But if not, spend more time with the slower leakdown test to be sure.

However, another possibility for low cranking compression is incorrect valve timing. The cylinders aren't able to breathe and compress the air properly if the valves open or close at the wrong time. This is one of those things that make me go, "Hmmm". Just thinking out loud here, but what if you had replaced the timing chains and the marks were inaccurate? You could repeat the assembly process 10 times, and consistently get the same erroneous results. I'm not sure how the cams are timed relative to the crankshaft, but is it via special marks on the chains?

While you're stewing on that possibility, I highly suspect you've got more than one fault active. The one that really grabs my attention is code P0355. See the explanation here, on page 35:

http://www.jagrepair.com/images/Auto...tos/P20003.PDF

This isn't just a generic misfire code, i.e. low power has been sensed from a particular cylinder. Those are codes P0301 through P0308. This is the computer saying I'm not happy with coil #5. This could be a wiring problem, but the most likely culprit, in my over-inflated opinion, is a bad coil.

Please note such a code would be totally separate from any possible compression issues. Even if your poor engine has zero compression but eight good coils, you should not have that P0355 code. You mentioned swapping coils around for troubleshooting, but did you move that one?

And just to be sure, please see page 3 at the same link above for cylinder numbering.


For giggles, please see this thread on an XJ8. The original poster had a long laundry list of fault codes, but one was P0355. He replaced that coil and all was good:

https://www.jaguarforums.com/forum/x...99-xj8-226755/

Important detail: The cylinder numbering shown in that thread does NOT apply to your car.