2007 xc70 no power to coil No. 4 - 5 cyl turbo

[raquette]

compression 120 #.

Tested cylinder 4 misfire: the coil wires green/white has constant 12 v and the brown wire flashes, so coil is receiving power.

I am beginning to think cylinder 4 injector is casing the misfire, will look into that next.

Thanks Abscate for your input!

[vtl]

Compressions should be more like 150+ PSI. But you've probably tested it on a cold engine, which may explain it.

[raquette]

checked out the injector, all working,

so to recap have power to coil 4, constant 12v on green/, pulse on brown coil wire.

time to take it to the shop I guess.

[93SCMax]

I may have missed how the #4 coil and #4 injector were deemed good (not working mind you). If you have a new spark plug and known good voltage, you potentially have a coil, injector or compression issue. How do you eliminate each w/o going to the shop?

Did you swap a good coil with the suspect coil?
Are you comfortable with the compression reading?
Could the injector be clogged and just need cleaning?

Things to ponder before going to the shop. Your call.

[raquette]

yes - swapped coils from good firing cylinder(s), and with spare coils, issue stays with cylinder 4.

swapped injectors and issue stayed with cylinder 4

code no. 4 misfire

when removing coil 4 plug engine rpm does not noticeable change like other cylinders.

plug 4 is black but not wet

This thing is kicking my butt

I'm beginning to think it may be a valve issue although compression is 120#

[raquette]

update: blue spark on coil 4 when testing plug on the cylinder head. swapped injectors and cylinder misfire code stays with the cylinder 4.

pulse and constant 12 v to cylinder 4 injector.

engine running on 4 cylinders - misfire code comes on after up to 50 miles of driving, but misfire from the drivers seat is constant.

[abscate]

The misfire codes don’t set right away.

Can you pull the injector and see the pattern?

[raquette]

I have swapped injectors and misfire stays on 4.

I tried cleaning injector 4 with MAF cleaner and could not get suitable attachment to the aerosol to check the flow pattern with 12v battery.

[vtl]

Can you do a leakdown test in #4? I wonder if the valves are not sealing properly (cavities on exhaust valve's face, or not enough gap left between cam follower and the cam).

[raquette]

I ran the motor with no. 4 spark plug laying on the head (grounding) and have nice blue spark spark with the engine running. So I'm leaning towards potential mechanical issue in the valve train.

I'll double check the compression (had 120#), and also insert air into the cylinder and listed for air escaping out of the the exhaust pipe or intake.

listening to the exhaust pipe when running, hear a continual miss out the pipe.

no obvious intake leak found.