Hi all.

I'm new to the forum, so hope I am following the right protocols.
Getting straight to the point over the past number of months my xk8 started with the odd intermittent random missfire, engine light would come on and error codes suggested random missfire but generally point to cyl 2 and 6, sometimes other cylinders. I reset these a few times after recording and notifying my mechanic. As it got worse to a point that i put the car in the garage and asked mechanic what to do.
Little history.this mechanic put in a reconditioned engine in this car for me a year ago. So he was well familiar with the car.
He dropped by with a new coil. But couldn't reproduce missfire while he was there. And suggested it may have been bad fuel?
Anyhow within days the misfire was back but now it was persistent rough idle, and had a rattle. So I quickly turned it off. Hesitantly I started it a couple of hours later but no rattle just rough idle.
So I dropped it at garage. Mechanic has had it for 5 weeks. He has replaced 3 coils, all spark plugs and 2 fuel injectors. Checked fuel pressure, wiring loom and tried even swapping the ECU with a spare. We were in contact throughout , so I'm giving the shortened version here. On a couple of occasions he said he had pressure tested the cylinders but all cylinders were fine. Now he called me to say that he redid pressure test cold and pressure was fine. Then he did the pressure test hot, I..e after running the engine for sometime and cylinder 6 was down at 130 while all other cylinders were at 190. So now he suggests the engine needs to be stripped back to see what's causing low pressure? So far I'm in for a lot of dough and not sure whether I can stomack going further? All along mechanic believed problem was electric due to fact the engine light was coming on? When I quizzed this he said he believes the knock sensor is over cylinder 6 and this was activating the random missfire error.
Any suggestions, thoughts. Would really like a professional second opinion.
Was looking at Amteck restore as an inexpensive trial, but thought maybe check in the forum first.
Really appreciate any feedback.
Thanks

 

Sounds like almost exactly what I just went through with mine. First I swapped coils between cylinders, replaced all plugs, replaced a fuel injector, sent ECU out to be tested, swapped ignition modules etc. Same problem. Even eventually got a noise. Turns out replacing ALL the coils fixed it. The noise was coming from inside one of the coils arcing internally. If your car has all the original Denso coils that could be the problem. Thats why swapping one or 2 makes no difference because there are multiple bad ones. And that seems to confuse the ECU and it doesn't list all the bad ones especially if some don't fail until after warm up. My car was out of commission for 2 months over this crap.
Does the low cylinder stay low if a little oil is added to it and the test repeated?

Here is the thread on my car...


Oh and Welcome to the Forum and if I don't someone else will ask to please tell us more about yourself in the New Member Intro section here.


Dave

 

Reconditioned engine and rattle stands out to me. You have a 2002, many of which where after the secondary tensioner upgrade, but what is the vintage of your reconditoned engine? If the state of the timing tensioners is not known, they should be inspected and the cam alignment checked. Your camshaft could have skipped a tooth.

 

Thanks for input guys.
I was assured that the recon engine was same vintage and it had the latest metal tensioners.
Hmmmm. I'll follow your treads and take it from there.
Thanks again.
Much appreciated.