I purchased a 1996 850 Turbo with about 212K miles in Oct 2011 (odometer has been broken for years). The engine runs great and pulls very strong. Recently, the engine began to "die" for a split second (blink of an eye) while driving, like the ignition or fuel was cut-off and then all was good again. Now while idling at a light, periodically, the engine may stumble a bit, pick up rpm's and then level out, then drop, then level out. It is not like the engine is mis-firing, just trying to shut down. Once I get going, the engine is fine, except for a slight stumble. I am also getting an occasional P0103 (MAF) code. I replaced the MAF 4 months ago. The car does not smoke while idling or cruising, but when coming off boost, there is about 2 seconds of gray/black smoke. I have already performed all the routine maintenance items, plugs, cap, rotor, wires, air filter, oil & filter, etc. I do not have excessive crank pressure. All vac lines are good, induction pipes have no holes/leaks, wiring and connectors appear to be in good condition. Compression is: 115/110/130/132/130. This seems low to me. I did add oil to the low cyl's and the numbers went up about 10 psi. In-tank pump is working, but I have not checked fuel pressure or the regulator yet. No gasoline leaks or smell anywhere. Help! I love this car! Classic red, looks great and fun to drive. Lost on this one...any help would be appreciated. Not sure if my pic uploaded.
https://www.facebook.com/photo.php?fbid=3052425422159&set=o.286104214215&type=1&

You mention in your post that you are now using premium fuel.

When your car senses pre ignition it adds fuel to cool the cylinders - changing the timing like most people assume will not work as it is already firing before the ignition system fires.

This might account for some of your better mileage and decreasing of smoke.

Hang in there on your compression - I purchased a 744 TI with 153k miles - its compression was poor in three cylinders - after 50k miles of 3k oil changes, two of the bad cylinders were up to snuff and the third was half way there.

My compression checks were done by Volvo techs.
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'96 855R,'64 PV544 driver, '67 P1800 basket case, '95 855, '95 854, the first three are mine, heh, heh, 485,000 miles put on 9 bricks

James,

Thank you for your input.

Apparently, it was the MAF causing the increased fuel "dumping" upon deceleration (stupid MAF!). I made the serious error of buying an aftermarket MAF (not OEM-BOSCH) and it failed in 4 months!

After replacing the aftermarket, NOT with a new one, but one I scavaneged from a 1998 V70 in a junkyard for $30, it is now running better than ever!

LESSON LEARNED: ALWAYS REPLACE SENSORS WITH OEM!

Greg

Well, nobody answered my problem, so I continued to look for issues on my own.

The stumbling turned out to be the MAF.

I made the (stupid) mistake of buying an aftermarket unit for less $$$ and simply got more headache.

Lesson to be learned...WHEN IT COMES TO SENSORS, BUY OEM! (or better)

The engine runs fantastic now. The low compression will have to monitored.

Sorry I missed your post! I would not have gotten the answer right, as you already stated that you replaced the MAF. I am going to have to start asking where the parts come from - like O2 sensors, etc.

As to the low compression, they are all TOO low. Check the compression again, but this time do it when the engine is warmed up a bit. If you check it cold and you leave the injectors turned on, you wind up washing the cylinders with gasoline and washing the oil off the rings. A cold piston and rings also will not have expanded enough to give you a good reading.

Find someone with VADIS to read the mileage on your car and then fix the Odo. I don't want you to wind up with a broken timing belt.

Klaus
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My name is Klaus and I am a V ♂ lv ♂ holic

One more thing...the engine always ran okay, but felt like it had a lot more to give.

I was curious about low cost performance add-ons, so I built and installed a manual boost controller and calibrated it on my workbench at 11 psi. Everything else on the car is completely stock. Running premium fuel now. WOW! What a difference! This has made a significant change in my SOP-ometer. Pulls like a freight train! Many more smiles while driving! After 250 miles, MPG is same or better. My friends can't believe this is "just" a 2.3L motor.

Are there any issues I should keep an eye out for? Is this safe for the engine long-term?

Note: I also installed a hidden ON/OFF BC bypass valve for when my wife or kids drive the car.

Thanks, Greg

If the boost gauge gets over 20psi, you could damage wrist pins.

Which dash light doesn't work? If you ever go into the dash again, using a pencil w/eraser in a drill works great at turning the odo. Sweet talking a dealer into reading the actual miles from the computer would be nice to know.

My 1995 would cause both front wheels to spin as soon as the speedo passed 25mph, when the tracks turns itself off. A little harry in the wet!!!

Klaus
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My name is Klaus and I am a V ♂ lv ♂ holic

Klaus,

The 4 upper gauge bulbs are fine. The lower-right LCD panel light will not work. The left one is ok. Funny how everything was fine until I installed a "new" light. I'll fix this sometime later when I have nothing to do.

Greg

Thank you for the reply, Klaus. When I bought the car, the odo was showing 137K, but with docs I found in the car and my friends statements, we determined the car had somewhere around 212K. I was informed the timing belt was replaced 1 year prior, but I bought one anyway to replace some upcoming weekend.

Since replacing the MAF with a BOSCH (spelled OEM) sensor, the "off boost" smoke has stopped. Can the MAF cause the ECU to signal additional fuel when the need is not there? I thought the turbo oil seals were shot, but maybe not.

Last weekend, I fixed the odo gear and left at 137K and also replaced the 6 lights, although none were burned out. Guess what? One of the "new" bulbs is not lighting!!! Arggh!!! Lesson learned: Turn on the lights BEFORE closing up the dash!

Thanks for all your input.

Greg