05 xc90 cracked wires from coilpack..

CainXC · Post by **CainXC** » 09 Oct 2014, 11:31

Already replaced plugs with new ones. And already swapped coils and problem stayed on 4. Did a compression test and got 120 on cyl 1&2 117 on 3 and 118 on 5. Cyl 4 I couldn't get a reading on. Just stayed at 0. There is exhaust coming from the oil dip stick tube. Could it be a clogged pcv valve? Would that mess with the compression?

Post by **rmmagow** » 09 Oct 2014, 12:12

Sounds like a bad valve, probably burnt. Best think about removing the head. I don't know if the valves are easy to get to but sometimes one can get to the valve, wedge a piece of metal tube on the top of the valve and gently wack it with a hammer to maybe jar a stuck valve loose, but burnt is more likely. Have a leak-down test run. Your car has a PCV system, not a valve.

Post by **jimmy57** » 09 Oct 2014, 12:19

No, crankcase breather system being plugged will not affect compression.
You have consistent flow out of the dispstick or definite strong pulses?
Strong pulses could mean cracked rings or something else deep inside.
I would suspect burnt valve as the more likely and historically predictable fault for no compression.
Put that piston at TDC valves closed. You can do this with a ping pong ball dropped into spark plug recess.
Crank engine over with a breaker bar and socket on crank nut and when the ping pong battle rattles the valves are closed. Even with a burnt valve the piston will push air enough to bounce the ball off the spark plug hole. Now use a long screwdriver doen in the hole and turn crank back and forth to determine TDC. turn the crank until the screw driver begins to fall and then reverse and find the same thing in the other direction. Split the distance and that will be TDC. Now you can apply air to the cylinder with something rigged up using the compression tester. When the cylinder is aired you should be able to listen and find where air rushes out.

CainXC · Post by **CainXC** » 09 Oct 2014, 12:55

It seems like a constant flow. I'll have to check again when I get home from work.

bruno12 · Post by **bruno12** » 11 Feb 2015, 15:12

Really interested to hear what you found! Chasing the same issue today on my '05 XC90 2.5T and I've even done the same as you, moving coils, plugs, etc. I haven't noticed cracked wires, but after a bad breather pipe, and oil everywhere, I wouldn't be surprised the insulation could be deteriorated.

So let us know what you ended up deciding on yours! I'll come back with mine if I ever find out. Testing compression and injectors tonight...