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’94 850 N/A with 105,000 miles.
I don’t know what to think about this engine. It’s got a slightly lumpy idle and miss at low RPM pulling, say at 2000 RPM and pulling a hill. It also burns about a quart of oil every 500 miles. No real leaks, a few seeps around the cam sensor and distributor, but nothing major. Several months ago I checked compression. I know had one cylinder with low compression, about 120 PSI in #5 AFAIR. A teaspoon of oil helped. Vacuum was good with a steady needle, so it seemed the rings in #5 were worn/broken/or scored cylinder. No codes.
Today I changed oil and checked compression again. Compression today was
165/168/171/180/165 hot. A teaspoon of oil raised them all by about 5 PSI. Vacuum is still a steady needle at 18" idle, 20" at 2000 rpm. WOT, the vacuum dropped to 0, and recovered to 23“. Plugs looked good, two maybe a bit lean, but none with oil fouling. I've still got a slightly lumpy idle, and still burn a quart every 500 miles. No leaks, but the seeps remain. No oil on a piece of cardboard under the engine overnight, after running the prior day. PCV hoses and oil trap were done about 5000 miles ago. Flame arrestor has been removed. How's the oil getting burned? Why do I have a lumpy idle? Plug wires are only about 2 years old, as is the dizzy cap and rotor. No carbon tracking in the cap or on the rotor. Plugs are Volvo branded, no excessive wear. Still no codes.
Any ideas?
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UPDATE!
I changed the oil and added the Auto Rx treatment about a week ago. I drove the car a lot this week, added 800 miles. So far I've burned less than 1/2 of a quart of oil, which is a big improvement. What does this say? Too soon to tell. It may be the Auto-Rx really works and cleaned off sticky oil rings like I hope is the only problem, it may be the car doesn't burn as much oil on the highway, or that simply fresher oil does not burn as fast as dirty oil. Time will tell. I'll get to add another 350 miles this weekend.
I haven't had a chance to follow Klaus' advice on cleaning the small hose to the PCV, and the car still idles a bit rough. I'm hoping that will fix it. I'll also add a bottle of Techron to the gas this weekend to see if I can clean up the injectors a bit, see if that helps.
I'll keep everyone posted.
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If you are going to run the AutoRx much longer, I suggest replacing the filter now. It could be filling up with some good crud. The filter replacement means adding about 1 quart of oil back in.
If the oil separator was gummed up, causing a lot of crankcase pressure, and the AutoRx cleaned it out a little, that will help the consumption of oil you had.
When you dump the dirty oil, replace it with synthetic to keep the engine clean.
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My name is Klaus and I am a Volvoholic.
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The oil seperator is only a few thousand miles old, it was one of the first things I tried when the oil burning became bad. It was clogged. I got the kit from FCP Groton, that included all the hoses and seals.
When I did that job, I was able to peer inside the block at that point, and it wasn't bad. Neither was it bad under the oil fill, nor did I get much sludge when I put my pinkie finger in the oil drain plug hole. Still, when I return home tomorrow, I'll change filters and top up the oil.
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posted by
someone claiming to be gwen
on
Sat Feb 21 04:14 CST 2009 [ RELATED]
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The problems with your engine make it seem like it has 268,000 miles on it instead of the 100K...
You can have good compression and still have oil leaking past the rings or you can have worn valve guides that will allow oil to pass and burn. 500 miles/quart wouldn't cause much blue smoke.
Haynes says compression should be between 185 and 213psi with no more than 28psi difference between cylinders....your a bit low, but not out of the ballpark.
Haynes lists the folling items that could cause bad idle......
1...worn timing belt
2..plugged pvc valve or leaking egr valve
3...faulty fuel pump not delivering enough fuel (pressure test the rail) 4.39psi
4....leaking head gasket (pressure test the engine
5...worn lobes on camshaft
6...vacuum leaks
In any case, it sounds like your going to need a new car or engine soon...
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The weeping cam seal still bothers me. Check the small vacuum hose that goes to the PCV, It might be clogged farther up than just at the end. Your vacuum pressure readings are too high at 2000 rpm.
If the cam seal is leaking, it will not leak after engine shutdown - no pressure then. It will only leak when driving, and 500 miles/quart is not a huge leak.
What's your gas mileage these days? It should be very good.
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My name is Klaus and I am a Volvoholic.
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Hmm, OK I'll check that hose. I *think* I checked it at the PCV replacement time.
Yeah, Mileage is good, 24 overall mix, 30-31 on the road.
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With the mpg that good, I would suspect that 1 or 2 injectors may not be delivering enough gasoline (dirt). You could get them cleaned or live with a slightly lean engine :)
But, still check out the small vacuum hose and replace the rear cam seal.
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My name is Klaus and I am a Volvoholic.
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I'll check teh vacuum hose for sure. You seem to concerned that teh cam seal is really, realy bad, beyond losing a drop or two of oil. And either you missed that the dizzy also has a bit of seepage, or you don't see that as problematic, so I am a bit confused.
I guess I'll mosey over to Bay 13 and see what's involved with cam and dizzy seal replacement.
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A leaking cam seal will push oil all over the place. My real concern is that the crankcase is not venting properly. I would just replace the small line from the PCV to the vacuum tree, making sure the hole in the tree is not clogged either.
As you can see from the pics on Bay13, the rear cam seal isn't hard. The dizzy seal is a bit more involved, but not excessive.
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My name is Klaus and I am a Volvoholic.
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Oh, and Klaus, thank you for all your help!
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Those compression numbers are low, which is surprising. They should be 185-210 in a NA engine. I also don't like that the rear cam seal is leaking a little. Have you replaced the seal in the oil filler cap? And the O rings on the dipstick?
You vacuum readings are good.
It could be that the cylinders were washed with gasoline and the added oil helped seal the gaps. I would worry that one or more of the injectors was clogged and/or not spraying correctly.
Does this car get driven much? Is the gasoline any good?
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My name is Klaus and I am a Volvoholic.
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I was reminded by a friend that I should have had the throttle at WOT during the compression check. I knew that but forgot. I wonder how much difference that made? I'll re-test both with my gauge and another.
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I've not replaced the ring on the oil cap, there doesn't seem to be any seepage here, nor at the dipstick. When I speak of seepage, it's pretty minor: I can wipe it off and squirt the residue with either carb or brake cleaner, and by next oil change, it's a film with some dust in it. Maybe only a few drops, although it should be dry.
It's been my wife's car for the past few years, and was driven little, perhaps 5,000 miles a year. Occasional long trips to full warm it and all. In the last two months, it's become my primary car and gets driven 150-200 miles a week with some longer road trips. I probably drive 15,000-20,000 a year.
The compression test was before I changed the oil, I can't imagine that it would change just because of fresh oil, could it? I must say the the oil I drained was surprisingly black. I always use a Mann filter, but don't know what the prior owner did for maintenance. We got the car with 65,000 miles on the clock. I do have suspicions about the accuracy of this compression gauge. I dropped it hard once, and on one known good engine wouldn't read over 90 PSI. A few raps and it read normal pressures for that engine. Still, it may be bad, I'll borrow a friends and re-check.
This oil change, I added the Auto-Rx you suggested, though to the oil like they recommended. I emailed them about adding a bit to each cylinder, but their response was that it would not be beneficial, that it works slowly and would be burned off well before it would be of any benefit.
I'm still puzzled about how I can burn so much oil, yet the plugs are not oil fouled. And of course, that idle. My wife and all but motor-heads that ride in the car do not notice it...it's like one cylinder just is not up to snuff, but firing some. It's more a sound than a vibration at idle,very regular, but if almost lugging the engine, it becomes more obvious and can be felt. As far as injectors, that was one of my early thoughts, but a couple bottles of Techron did not change a thing, and that's when I first checked the compression.
Does any of this give you any more clues?
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The very black oil is an indicator of blowby at peak compression and ignition, ie. the exhaust pressure was too much for the rings and your rings are either stuck and/or there is scoring in the cylinder wall.
The early 850 NA engines do not have oil spray nozzles to coat the cylinder walls like the turbos, they rely on the crank splashing the oil. This means that the NA engine should be turning at least 2000 rpm for a good bathing.
Your wife and previous owner probably did very little in the way of spirited driving and mostly left the engine oil cold after short trips. There should be a lot of gunk on the bottom of the oil pan, so with the AutoRx be prepared to change the filter a couple of times. When changing the oil, make sure the oil is still warm, just don't burn you fingers!!
You may have to live with this problem. Removing the head is too costly to just look at the rings, and if the rings did score the cyl it would be time for a new block/car.
With the miles you now put on the car daily, you could try upping the viscosity and see if that helps.
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My name is Klaus and I am a Volvoholic.
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I was guessing that the black oil was due to blow-by. I've always encouraged my wife to let the engine rev to at least 3500 before shifting, and she usually goes to 4,000 or better. NOw if I can only stop her from using the clutch to hold herself at a hill....Married 15 years, and haven't succeeded yet...
I Just finished checking the compression again this time remembering to keep teh throttle open (duh) What a change, but also odd #1 went from 165 PSI to 187 (12 PSI) #2 went from 168 to 180 (12 PSI) #3 from 171 to 190 (19 PSI) #4 from 180 to 185 (5 PSI) and #5 from 165 to 182 (18 PSI).
While it is all still lower than you say it should be, it's not so bad. What is really odd is the difference between teh increases...from only 5PSI to 19 PSI. Both times the engine was hot, and no oil added.
I don't understand, but you are right about one thing: if I want to fix it, I guess I need a new engine...that is unless it's stuck rings and the Auto-Rx frees them.
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Fantastic!!! 187, 180, 190, 185, 182
Nothing wrong there, given the age of the engine. Do NOT take this head off, you won't find any problems. Maybe a little carbon buildup in #3, but not bad.
You could be burning a little oil through the valve seals, but it is cheaper to add a quart every 500 miles than it is to replace 20 seals.
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My name is Klaus and I am a Volvoholic.
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OK. We'll see what teh snake oil does. If it fixes it, I'm happy if not, I'll just deal with the oil consumption. What do you think about this odd idle? I only lug it to test, but pulling at low rpms it's almost a miss. Feels like a burnt valve, but my vacuum readings say 'no'.
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