I'll be upfront in that I'm not nearly experienced with 850 and FWD Volvos as I am with a 200/700/900 RWD Volvo. A friend of mine bought this particular car pretty cheap and was hoping that I could fix it for him (I take care of his 3 other 240 wagons for him).

The car: a '93 850 GLT (non-turbo), 193,000 miles and the last timing belt was at 79,000. The previous owner did a nice job of neglecting it and I spent the better part of today catching up on the neglected service items: clogged air filter, flame trap and PCV cleaning, oil change, fouled spark plugs, plug wires not spaced correctly (arcing between themselves), etc, etc.

On the first test drive the car ran better than when the owner brought it home, but still rough with a noticeable miss. A quick compression check yeilded the following numbers:

#1 = 152 psi
#2 = 155 psi
#3 = 155 psi
#4 = 0 psi
#5 = 135 psi

I've confirmed that the #4 cylinder does indeed have spark, power to the injector, and the injector gets louder when plugged in (usually indicates it's functional). Disconnecting or re-connecting the #4 injector does not yeild any change to the car's RPMs or the noticeable miss.

When compression checking the #4, the engine free-wheeled (during cranking) with no resistance, which leads me to believe that a valve might be stuck open. I poured enough oil into the cylinder to be sure to overfill the dished piston and saturate the rings, and then rotated the engine a few times. A re-check of compression yeilded another zero psi. I would have used fogging oil, but none was available and the local stores are closed at this hour.

I then took the car for a 15 minute test drive, in first gear, and keeping the RPMs between 4,000 and 6,000 (redline) in hopes of freeing what I suspect is a stuck valve. -this was an effort to mimic the procedure used to free stuck valves on a 960, where you would drive the car at 5,000 rpms for an extended duration and allow the synthetic oil to clean out the valve stem. Unfortunately, this car only has fresh conventional motor oil in it, and I'm not sure if that procedure will work on an 850 engine. Anyone out there have success with it? I had no improvement with the 15 minute test drive.

I'm wondering if the timing belt may have slipped a notch or two, thus causing the low pressure in the rest of the cylinders (and possibly a bent valve in #4). I'm also wondering if anybody out there has had sticking valves before on this engine. -or any thoughts on why the cylinder is dead (blown head gasket?)

Your thoughts, comments, advice, and prayers are welcome and appreciated.
God bless,
Fitz Fitzgerald.