Fitz,

Just pulled the head on my son's '96 850 with the exact same conditions you indicate but in our case the dead cylinder was #1. Found a valve completely burnt. Car probably was running sub par for some time but finally just hit the end since the 5 cylinder is always a bit odd for most people.

I'll re do his since it only has 113K miles on it. In your case it is a toss up because it is a 93.

Good luck,
Tim

Today I spoke with the best Independant Volvo Mechanic in the area (4 years of Volvo School in Chicago, plus several years at the dealership until just recently). He more or less had the same diagnosis as the information that you fellow Brickboarders have listed here. He also confirmed the though that if one valve were bent, more of them should have been too. His over-the-phone diagnosis was suspecting a burnt valve, or a collapsed lifter which in turn left the valve extended and it got dinged by the piston as it came upwards. Either way, it means that valve work is required which also means tearing into a complex engine on a car that has a Blue Book value of $2,000 to $3,000. If it were a RWD red-block engine, I'd do it in a heartbeat. However I'm going to let the owner decide the best route to take. He may wish to part it out.

"It sounds more like you have got a burned valve than anything else...Doing it yourself is obviously considerably cheaper so long as your time is worth nothing."

Thanks, I appreciate the help. Unfortunately my time is not free on this project as it's for a client/friend rather than a personal vehicle. I will most likely defer to the local Indy Volvo mechanic on this one.

"I suppose you could always just unplug the #4 injector plug and have a four cylinder if you don't mind a little rough idle. Maybe even save a little gas?"

Thanks for the advice. Unfortunately for me, the extra air going through the system will throw off the O2 sensor as it thinks it's burning lean. It then enriches the mixture which causes the rest of the cylinders to run rich and foul the plugs. I pulled a set of very black plugs out before I preformed the compression test. On the other hand, I might disconnect the O2 sensor completely and let the car do it's best mixture assessment based only on the air temp and manifold pressure. -that would get it to burn a bit more accurately with a dead cylinder. The vibration goes away once you're above 2,500 rpms...

"The 1993 is not worth a great deal of money. Remember, many parts of the 1993 model are unique to that year and may be hard to come by."

Yeah, the thought had crossed my mind. I was able to identify the car over the phone by asking the owner if it had 4 or 5 lugnuts on the wheels when he couldn't remember the year. -I cringed when he said 4, as it means a lot of parts that aren't compatible with other model years.

"If a valve is stuck because of a bad valve guide, you would come out cheap. If it is a bent valve, which can happen when an electrode falls off a multi prong plug, then the head must come off...Removing the head is a non-trivial matter and gets expensive."

I'm fearing the worst here, and you're right, it may be more expensive to put the car back together than it's worth. I wonder how hard it would be to put a Red Block in there.....

"I would also check for a rear main seal leak."

I would suspect that it has a rear main seal leak even if I can't see it. Do you know what year was the final year for the bad rubber compounds in the White-Block rear main seals? I've had several friends that had to have theirs replaced on their 850s and S70s (at a cost of $800 each). I know the new rear crank seals have a new formula to them, but when did they stop making the bad ones?

Thanks again for the help and advice everybody.
God bless,
Fitz Fitzgerald.

Pull the head. It is a long and difficult job, but if you do it yourself it is practical. To pay a machanic is an iffy proposition. The car isn't worth a lot, and you'll spend $1,000 pretty fast.

An other option is to pull the head yourself and fix the problem, then pay a mechanic to re-assemble it, provided it is worth fixing. . Re-assembly is the tricky part. Taking it off is just labor, no really hard stuff.

The 1993 is not worth a great deal of money. Pulling the valve cover requires an expensive sealant to put back on, but that may be worth while. If a valve is stuck because of a bad valve guide, you would come out cheap. If it is a bent valve, which can happen when an electrode falls off a multi prong plug, then the head must come off.
Removing the head is a non-trivial matter and gets expensive. The timing belt cannot be 115K miles old without showing extreme signs of wear. I would also check for a rear main seal leak. Poor maint practices will lead to over pressured manifold gasses and cause seals to break.
A headgasket failure near #4 would create all sorts of other problems other than loosing total compression.
You won't know what is wrong until you take it apart, and the cost of putting it back together may be more than the whole car is worth. Remember, many parts of the 1993 model are unique to that year and may be hard to come by.
BTW, driving at 5000rpms is good for these engines. It causes the valves to rotate and free up.

Klaus
--
1975 164 w/174,800mi (Sold) 1995 850T w/91,000mi, 1998 V70R w/129,000mi

They all can be saved depending on how much $$$ you want to spend. Too bad the compression wasn't checked before you did all that other work. I suppose you could always just unplug the #4 injector plug and have a four cylinder if you don't mind a little rough idle. Maybe even save a little gas?

The Italian tune-up works on all white engines but it will not adress your problem. Your compression numbers are not that low and if your cam was off enough to bend one valve it would bend others as well. It sounds more like you have got a burned valve than anything else. The only other thing that I can think of to diagnose your problem aside from pulling the head is a cylinder leak down test. I have never used one of the el cheapo units from Harbor Freight but they do sell one and from time to time they put them on sale at blow out prices. Seeing as how the car is driveable you might want to drive it to the local independent and have them do it but it will probably be cheaper to buy the tool and do it yourself. If it is a burned valve as I suspect then it is time to either scrap the vehicle or pull the head and do a valve job. Depending upon what you find and how much the machine shop charges to make it all right it will typically set you back somewhere in excess of $1,000.00 to have it done in a shop. Doing it yourself is obviously considerably cheaper so long as your time is worth nothing.

Mark