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  #1  
Old 10-18-2011, 12:57 PM
AJN AJN is offline
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Default Any risks in driving with lost compression?

Hi All,

I am a new member hoping to receive some advice from an experienced Volvo driver. We have a 1994 Wagon with 250,000 miles and we would like to continue driving it, however it was recently diagnosed with lost compression in one cylinder. The car idles somewhat roughly, but is smooth at most driving speeds. We have been told everything from "you should think about a replacement car now" to " if you can put up with the rough running and it doesn't get worse, don't worry". Does anyone have any experience, advice or suggestions? Thank you!

AJN
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  #2  
Old 10-18-2011, 03:28 PM
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Loss compression is kinda broad but does mean one thing for sure, the motor has a serious mechanical problem. What is the compression on that one cylinder? Is the car turbo or NA? You either have a bad piston or bad valves on that cylinder. If the problem is valves, you can get that fixed cheaper than a bad piston. A head is easier to replace than the entire motor.

The car is likely missing on that cylinder. Do you have a CEL? It probably is missing all the time, at idle and driving at 2,000 rpm's. The difference is that you can't feel it as much when the motor is reved. The 5 cylinder is one of the smoothes motor ever made and if only one cylinder is missing, you simply don't feel it as much as you would in a 4 or 6 cylinder car. You can keep driving it until you throw a rod or something. But if it's a valve that's bad, you may be able to get it fixed for under $900 (having the head rebuilt or a couple of valves replaced). That's just a guess on the cost, maybe someone else here can give a more realistic price.

A compression test can tell you weather it's the valve or piston. Some kind of leak down test they do.
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  #3  
Old 10-18-2011, 08:36 PM
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You could also have stuck rings. It's a condition where crud builds up and jams the piston rings in place where they can't follow the cylinder wall and you get massive blowby.
People can do leak down tests where they send compressed air into the offending cylinder and they use their ear at the intake, exhaust and oil fill to determine where it's leaking into.
If it's valves there isn't any "mechanic in a can". If it's rings you can try pouring a solvent or something into the cylinder to let it soak and hopefully free up the rings. It's the same idea if a vehicle has sat for years and locked up.
On the positive side, you are basically driving a four and a half cylinder. The other four are trying to make up for that weak one. In most cases you can drive and drive and drive it but it's going to run rough and you won't have the best gas mileage as you're wasting part of that fifth cylinder. Hopefully you are not in a northern climate as it will be harder to start the further you get below zero as that one cylinder isn't giving it its all. I drove a Cavalier (out of necessity) on three for over a year. My fourth was totally dead and knocking. I was amazed every day it made it home.
The other thing to watch is the catalytic converter. Since it is firing it's burning the gas but as compression lessons it's not as efficient. My cylinder was dead so all the fuel was being dumped into the cat and it never overheated or plugged but ..... it is a possiblity.
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Last edited by Kiss4aFrog; 10-19-2011 at 12:06 PM. Reason: spelling
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  #4  
Old 10-19-2011, 03:03 PM
AJN AJN is offline
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Default Thanks for the information and advice

Thank you very much rspi and Kiss4afrog. It always helps a lot to receive additional advice from the experts so I appreciate the time you took to reply.

I will definitely know what to ask the mechanic next time I take the car in ( it has had very regular maintenance ), and if they are able to give a more accurate picture of the exact symptoms, I should at least know the options by taking your suggestions and advice into consideration.

The engine is not turbo and I was told there was no compression at all on the problem cylinder. The one suggestion they did make was to NOT replace the head as that could potentially cause other problems to the older components.

We were warned about the catalytic converter too, and we have noticed a decrease in the mileage so we are experiencing everything you are saying. I am posting from Victoria, B.C. which has the same climate as Seattle ( Summer 50 degrees, winter 40 degrees ) but we do make the odd trip to a local ski hill, so we'll have to think twice about subjecting the car to sub-30 temps. Our wagon is no different than any other 17 year old volvo .... she is part of the family and we can't imagine life without her!

Thanks again.

AJN
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  #5  
Old 10-20-2011, 08:36 AM
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Quote:
Originally Posted by Kiss4aFrog View Post
If it's valves there isn't any "mechanic in a can". If it's rings you can try pouring a solvent or something into the cylinder to let it soak and hopefully free up the rings.
You may want to try a Seafoam treatment. Some in the oil and the rest sucked through a vacuum port with the engine running. Seafoam is made for issues like this. (Provided you dont have a physically damages component)
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  #6  
Old 10-20-2011, 07:25 PM
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One thing, did it all of a sudden start running rough or was it gradual?

On the seafoam, the other thing to try if it is stuck rings is toss a quarter to half a can down the spark plug hole so it saturates the rings. Let it sit for a couple hours or even a day or two. You can try it a couple times as you can't do any harm doing this. You wouldn't even need to change the oil as seafoam is an oil additive and any that leaks past the rings and into the oil pan won't do any harm.
What you have to remember is it might not all seep past the rings so before you try to start it you'd want to turn it over a few times (spark plug out) to push any liquid out. It might be a bit messy but you'd need to do it as if the liquid is left in there when you try to start it the engine can't compress the liquid and will lock up. I've done this to a few older engines I've worked on where they were locked up and it usually will loosen them up so they can be started. If you don't have a compression tester some auto parts stores loan them out so you can actually check it yourself.
The thing to do is find a friend, neighbor or mechanic who can pressurize that cylinder and determine if it's rings or valves. With air going into the cylinder what you would hear is a hissing at the oil fill. If you can hear it coming out the intake or the exhaust it's a valve and you can only fix that by taking the head off that I know of. It could also be a bad head gasket but in that case you'd have overheating and coolant loss issues that you haven't mentioned so far.

"The one suggestion they did make was to NOT replace the head as that could potentially cause other problems to the older components."

This I don't understand because to fix the problem it would be the only way to go in and do any kind of physical, mechanical repair.
For a customer wanting to pull some extra horsepower I'd warn people about putting in a better cam and new or remanufactured heads on an older engine because your are putting way more strain on the old rings and if they go after you've done that work the engine would have to come out to do the rings. But for a repair other than using something in the oil or pouring it into the cylinder you have to pull the head off.

I just had something sink in from your last post. I was thinking low compression. If the cylinder has no compression it's more likely a valve. There are usually two to four rings on each piston and to have all of them fail is pretty unlikely. They can break, do wear out and then can get stuck from sitting and or bad oil, poor change interval or ingesting some water. But for it to be just one cylinder doesn't make sense for rings. You can try the seafoam but I think it's more likely something with the valve train.
I'm pretty good with a wrench but I'm not an expert. My opinion is just one more in the chorus. This is my first Volvo.
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Last edited by Kiss4aFrog; 10-21-2011 at 10:58 AM. Reason: No compression
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  #7  
Old 10-21-2011, 06:35 PM
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@#%$&

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  #8  
Old 10-21-2011, 09:11 PM
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I just went through a similar situation over the last couple of weeks with my '94 N/A.

We had just gone through the fuel tank recall where they replaced the fuel tank. A few days later the car started to run like crap and according to my wife it was sudden. I need to temper that remark with the time she called and the car only had one lug bolt on and it was loose - that was sudden too.

Given that the gas tank and fuel system had been recently messed with I figured it was a fuel problem. The pressure checked OK so I started unplugging injectors. The #1 cylinder injector made no difference whatsoever when it was unplugged.

I dumped 1/3 of a can of Seafoam into the gas tank and after 100 miles or so it wasn't getting any better. I have 5 of these things and it is getting increasingly difficult to remember what I did to which car last so it dawned on me that I may not have changed the spark plugs in the last 50 or 60 thousand miles on that car and I run the dirt cheap Bosch coppers.

I changed the plugs but no joy. At that point I pulled out the compression gauge and found that cylinder 1 was only at 90 PSI - the rest were in the 160 PSI range and that number may or may not be good since it is a $20.00 Harbor Freight gauge. I do believe the gauge to be accurate in relative terms though.

Zero PSI tells me a valve problem but 90 PSI looked more like a ring problem.

I dumped another 1/3 of a can of Seafoam into the crankcase and then drove the car 40 or 50 miles round trip out to a NASCAR race but things didn't really get any better.

Last weekend I went ahead and yanked the fuel rail and drowned the injectors with carb cleaner. After I put things back together there was still no joy.

My wife had pretty much put the car into "time out" because she was mad at it which meant that she was driving my Plat to work and I used her car to go to the Quick Trip the next day - magically - the car was running like a top again. At that point I was so happy with it that I slurped Seafoam into the intake and let it rest for about 30 minutes. I have never seen a smoke cloud like that it my life after I restarted the car but I quickly left the neighborhood (My next door neighbor works for the EPA) and after fogging the nearest highway for 5 miles or so no more smoke and the car runs as well as it has since I bought it with 140k on a broken odometer. I'm over 260 k miles (on a fixed odometer) now.

I have not redone any compression checks so I don't know what the numbers are - my wife is happy so I am happy!

A really long story short (Executive Summary) - A Seafoam treatment might help but if your compression remains at zero I would just unplug the fuel injector electrical line to that cylinder if you are going to continue to drive it. There is no reason to dump fuel into a cylinder that it will never burn in and it can actually damage the catalytic converter.

...Lee
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Last edited by Ozark Lee; 10-22-2011 at 02:50 PM.
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  #9  
Old 10-21-2011, 11:44 PM
AJN AJN is offline
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Default Now I want to solve this mystery

Thanks all for the advice, suggestions and stories ..... now I don't feel that I'm the only one with this problem! It does sound more and more like it's a valve issue. There is no compression at all in the cylinder ( I don't recall which one ) and the problem built up over time. As far as going with a remanufactured head, we were told it would put strain on the old rings etc ( I may have got that wrong the first time ) but as you say, it probably has to come off at some point so we'll have to do something.

The leak down test sounds like the next step, and I'll look into removing the fuel injector electrical line if that will prevent fuel from being wasted and eventually causing catalytic converter problems.

We too have a dead odometer Ozark Lee, it stopped at 380,000km so I guess we'll never know when we hit 500,000! I have to ask another question: We are still on our original muffler, is this typical? We used to have a Volkswagen Jetta and it seemed we replaced the muffler every other oil change.

Thanks again for all of your input ....very much appreciated. I had no idea there were so many experts!!

AJN
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  #10  
Old 10-27-2011, 04:52 PM
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Quote:
Originally Posted by AJN View Post
We too have a dead odometer Ozark Lee, it stopped at 380,000km so I guess we'll never know when we hit 500,000!
As for the muffler, I can't believe it's the original but ...... I've never seen anything that wasn't stainless last past 100K and most go a lot sooner.

As for your true mileage the car keeps a record that you can pull out of the computer.
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Old 10-27-2011, 04:52 PM
 
 
 
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5th, 850, car, compression, compresson, cylinder, drive, driving, hasmloss, leak, loss, lost, s70, test, turbo, volvo


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