98 V70 T5 Crap Idle/Performance after engine is warmed up

[tryingbe]

Don't drive it until you get this problem solved. Excessive gas in oil will wipe the bearings and toast the engine very quickly.

[850n00b]

Just a thought...could a bad O2 sensor make it run like this, even though CEL? I'm not too familiar with Motronic Engine Management, but on the older Mazda OBD1 systems, the O2 sensor was ignored prior to closed-loop operation. Is this the same habit for Motronic 4.4? I haven't touched the car in over a week. Been dealing with getting a Saturn running for the wife since her Durango crapped the bed.

The O2 sensor I have installed is a Bosch unit and is about three months old. Since I already bought the CLT, that's going in this weekend. May pick up an NTK O2 sensor if I can find one on the cheap.

[850n00b]

Diagnosed burned valve. 185psi in all cylinders except #4, where it was 125. I have a head being prepped so I'll start tear down and head swap within the next week. Can't wait to get this monster back on the road.

[erikv11]

Ugh. But that's a curious result, because a burned valve should give essentially zero pressure in that cylinder. Exhaust valve? Maybe it is just the tiniest of chips. I guess you'll know for sure once the head is off.

[850n00b]

Yup, and the reportedly "good" head I picked up has a cracked cam girdle (or cam truss?
)...I'm going to check it out tomorrow, the head shop said it was at the back of the head. It also needs a valve grind. May scrap it and get my original head repaired.

Ugh this beginning to be a nightmare now when I thought there was light at the end of the tunnel.

[850n00b]

Bump to this soap opera again

So it seems that the cam boss/thrust area on the exhaust side (timing cover) was cracked about 1/4 down. That would have been found. Machinist at head shop turned over paper, found that the deck measured 5.060", just a literal hair under minimum thickness for the head. He grabbed his micrometer to measure again, 5.060 on the distributor side, 5.030" on the cam gear side.

The damn thing is at a slant. But hey, at least it's flat, right? Time to rip off the head of my wagon and get it done that way. Was trying to save some time and busted knuckles.

[Ozark Lee]

That stinks. Out of curiosity, where did the replacement head come from? Was it a local yard or one of the re-builders?

We have an ongoing thread on replacement head sources right now, particularly Clearwater Cylinder Heads, so your source of the busted head is valuable information.

...Lee