Ok. So i have a 1998 v70 wagon with turbo. 253,000 miles on it. The guy before me put a new turbo on it. It had slight blow by when i bOught it. I have driven it three weeks no issues. The other day it started to spit and sputter . Came up with a cylinder #4 miss fire. So i bought new cap and rotor and plugs and plug wires. I replaced the cap and rotor. I took the cover off of the engine and pulled the wires. There was oil pooled up in cylinder #2 and cylinder #3. I pulled the plugs and did a compression test while i was at it. I came up with from left (front of engine by pulley) to right. #1 140lbs #2 180lbs #3 100lbs #4 140lbs and #5 170lbs. That was dry. I read to spray oil in the cylinders to try it wet. I do not have a oil sprayer so i poured a little oil in each cylinder at a time and all of the cylinders stayed the same except #3 which went from the 100lbs to 270lbs. I have not installed the new plugs and plug wires yet. Can some one explain to me what these numbers mean and what should i do? Also how can i tell if i need to replace the pcv system? Would that have any reason to those numbers? Thanks

 

on the turbos 140-180 dry is normal so #3 looks low. When you put oil in the cylinder the oil helps the rings seal up. So if your wet compression goes up from say 100 to 180 - you have worn rings or scored cylinder walls. If the wet compression was the same as dry then you'd have a burnt valve. I'd retry the wet test - 270 sounds like a misread or you put way too much oil in for the wet test - it should have gone up to 180-190 or so... Worn rings is consistent with your blow by comment. I assume the car burns some oil (ie more than 1 quart per 1000 miles?). Was the plug for #3 black vs tan?

To test the PCV system, there's some simple tests to see if air is being pushed out - ie through the filler cap or the dip stick. Look for some posts on the 850 forum for the "rubber glove" tests where you look for positive crankcase pressure. If the PCV is clogged the pressure usually goes out the dip stick or the filler cap. Clogged oil traps won't impact your compression but it can create oil leaks and lead to other issues.

You may also want to start by replacing the gasket for the oil filler cap as those do get old - or somebody was slopping filling the oil a few times which is why it was pooled on the head.

 

Thank you for the reply. I know the filter cap is New. I hope to finish putting it back together today or tomorrow. Then i will do the "white glove test" i have a feeling that the trap is clogged. As for the low compression i think i will just drive it the way it is once the miss fire is fixed. Thanks

 

sounds like a good plan. PCV traps get clogged mostly due to infrequent oil changes - which also can do in the rings. There's some good vids on YouTube for the DIY procedure for replacing the PCV trap/hoses. FCP also sells a complete kit for like $150 or so.

once you get it running check the #3 plugs color after a few weeks of driving to get a sense of how much oil may be getting into the mix...