2006 xc90 v8 misfire

[drosser]

[misfire video][/

Still chasing the misfire. Here’s what I’ve tried – swapped coils, no change.
Swapped injectors. No change.
All new plugs no change
Changed injector loom and fuel rail no change.

New FPR no change

New crank position sensor no change

Smoke test, no leaks.
Leaked down test, holds pressure.
Compression test- 190psi on cylinder 1

Suspecting it is valve stem seals, I put a can of motor oil saver in the crankcase. 28 miles later no change. I know the can says it takes 500 miles so still looking at that.

Grounds from pin three in the coil connections all have continuity with the valve cover, so all grounds seem good.


Any other thoughts? Maybe a loose wire that for some reason isn’t making connection at idle but otherwise does at higher revs?

Any other tests I can do?

[Krons]

Any codes?
(Sorry…didn’t take time to watch video!)

[Vova585]

It looks like #1 and #8 are on the opposite banks if the diagram I found online is correct. What is concerning is high misfire count on #1 in comparison to #8. I would probably try to check pindrag on the #1 coil connector. Use 5amp test light to see if the ground is intact. Same for the 12v side of the coil. I am not familiar with Yamaha v8 setup. Just questioning if there are any egr ports that can get clogged next to #1(using prius analogy). How many miles on engine? Valve seals is an interesting theory. However I would expect your spark plug #1 would be covered in oil deposits if such would be an issue. Psi also seems to be ok and leak down is amazing test. I assume spark plugs were OE or OEM from reputable source?

[drosser]

Still driving around with this problem. I added a second ground strap just in case the one in the valley was fraying- No change.

Plugs are all genuine Volvo. There is a discrepancy between the manual and the internet on the gap. Conventional wisdom says .44. That is what i have it at.

The only other news is that I can hear (and see in the dark) it arcing when it heats up. Very odd. Loud snapping and visible arc to the ground strap. Happens about every 20 seconds and is not regular.


Will try to pin drag the wires with the test light next.

However the presence of the arc seems to point to an unused charge and not that it isn’t getting enough.charge- almost like the computer is sending the wrong signal at cylinder 1 to the coil.

[ggleavitt]

V8 has an electrolytic capacitor in series with the coil pack ground path to body frame. Marked as 20/14 in the attachment. Doubtful that's your issue but worth omitting. Located by the rear motor lifting hook:

Capacitor XC90 V8.jpg (29.55 KiB) Viewed 360 times

Ignition Wiring_XC90_V8.pdf

(173.09 KiB) Downloaded 6 times