Hey folks, P5 with 168K. Noticed some pinging last 1000 miles. Checked for obvious vacuum leaks/cracked hoses, replaced the cruise control hose but made little difference (must've been barely leaking). Decided to go down the service manual list of things to check: ECTs are good, well under 241F, then check compression. Been running MP3 flash since I bought it, so it's had 93 gas all the time.
Compression numbers, with all plugs out, warm engine are: ~55, ~55, 115, ~117. When I bought this car with ~145K, the compression numbers were around 140. So 55 is ridiculously low--the car seems to be down on power a little, but not crazy much. Pinging under part throttle, sometimes under full throttle. Been running 93 and octane booster last 1000 miles or so (had some ski trips to drive on, heh, didn't realize the compression was this s***).
Poured a little oil into the low cylinders and it didn't change the compression readings, so I know it's not scoured piston walls. So it must be either valves or head gasket--perhaps blown head gasket in between cylinders?
The car is not overheating or running very poorly. I do get stumbly idle now and again, but nothing like "crap EGR" idle that I've had with P5s before.
ANy suggestions for next steps? Order a head gasket right away, or go have a leakdown test done to see if it's valves or HG?
Thanks!
Compression numbers, with all plugs out, warm engine are: ~55, ~55, 115, ~117. When I bought this car with ~145K, the compression numbers were around 140. So 55 is ridiculously low--the car seems to be down on power a little, but not crazy much. Pinging under part throttle, sometimes under full throttle. Been running 93 and octane booster last 1000 miles or so (had some ski trips to drive on, heh, didn't realize the compression was this s***).
Poured a little oil into the low cylinders and it didn't change the compression readings, so I know it's not scoured piston walls. So it must be either valves or head gasket--perhaps blown head gasket in between cylinders?
The car is not overheating or running very poorly. I do get stumbly idle now and again, but nothing like "crap EGR" idle that I've had with P5s before.
ANy suggestions for next steps? Order a head gasket right away, or go have a leakdown test done to see if it's valves or HG?
Thanks!