low compression in cylinder #4
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    1. #1
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      low compression in cylinder #4

      2005 v50, 97.6K miles. Starting a year or so ago, the CEL started coming on after a cold start~whole car shook.. Dealer mechanic said codes indicated all cylinders were misfiring. Replaced fuel pressure sensor (3 times), spark plugs (2 times). The CEL would stay off for a couple of weeks and then reappear. Tried several dealers....no luck. So I took it to independent Volvo mechanic who found that compression in cylinder 4 was low (came up very slowly to 135...other shot up immediately to 180). He said the problem was not the coils. Mechanic says that he has to open up, and possibly replace engine. But this is going to cost more than the car is worth. So he suggested that I just keep driving it because it is otherwise in great shape.

      Now, the CEL has started coming on after a couple of days and not necessarily after a cold start. Did an exhaust gas check in the radiator and no indication of head gasket leaks. Taking off oil filler cap- there is no blow by. Any ideas about what might be going on? I really love my car, but not sure whether it is worth spending the money to fix a 13-yr-old car (I bought it new). I have to have the car inspected, and as long as the CEL keeps coming on, it will fail. Soon I won't be able to drive it anymore.

      Thank you.

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    3. #2
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      I suppose you could ask your independent tech what he thinks of replacing the rings on that one piston, and the bearing on the connecting rod while he's in there, instead of replacing the entire engine with a used engine or rebuilding all of the one in the car.

      I'm just thinking how to save you some money, but he will probably say may as well do all cylinders while I'm in there. Even though the others don't absolutely need it since compression is fine on them. I wonder if he plans to rebuild the head with new valves and what not also.

    4. #3
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      A cylinder leakage test needs to be done to determine where the problem lies. But there won't be a cheap solution.

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    6. #4
      Global Moderator tmtalpey's Avatar
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      You should at least investigate the actual cause. It might be a valve, in which case replacing the head wouldn't be anywhere near as expensive. Even if it's a piston or cylinder sleeve, replacing the engine might still be a reasonable approach cost-wise. Did he try squirting oil in the cylinder to see if the compression improved (indicating rings/cylinder issue)? A borescope might give more information, as well.

      If you really love the car, and there aren't any other major issues, consider that even if the cost is more than it's "worth", the cost of replacing it is still going to be high. It can still make sense. Style-wise, these cars definitely age well, it's not like you're pouring cash into a Honda.
      2005 V50 T5 AWD 6MT w/Heico tune, Heico exhaust, Bell intercooler, IPD TCV, Viva Forge CBV, Elevate rear swaybar and torque mount, Snabb shift kit, etc.
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    7. #5
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      Hey that's not a very nice thing to say about Honda, Tmtalpey.

      Honda makes a great product and the resale prices are proof, not to mention, they have far less quality control issues than Volvo.

      Martaf, you could also ask your independent mechanic to perform a leak down test, which is different from a compression test. I think a leak down test gives indication on condition of the head but I can't remember for sure.

    8. #6
      Quote Originally Posted by Caspian3.2 View Post
      Hey that's not a very nice thing to say about Honda, Tmtalpey.

      Honda makes a great product and the resale prices are proof, not to mention, they have far less quality control issues than Volvo.

      Martaf, you could also ask your independent mechanic to perform a leak down test, which is different from a compression test. I think a leak down test gives indication on condition of the head but I can't remember for sure.
      +1. A leakdown test will give you an exact idea of the compression ring gap while cold and if the head has any large leaks in it. It will help determine if something is leaking somewhere, and if the walls aren't shiny.

      Just a question...you have 97k on this motor and your coils are all still good? Seems odd to me that the middle cylinder of all would have some sort of problem, especially since heat radiates outward through the block to it's corners rather than going towards the middle...especially when it's shut off and cooled down. These heads are usually pretty rock solid as long as oil changes have been consistent and normal.
      2006 Volvo S40 AWD T5 M66 - Dusty Rusty
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    9. #7
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      If you have a lot of misfires, I assume this is being diagnosed by codes? I'd think bad coils.
      The low compression could be a problem with the head gasket. Does the car use coolant? Has it been overheated or had a hose leak? I have a family member whose got a bad head gasket or crack in the engine somewhere. I tested for exhaust gases in the coolant but it never was positive. But the engine definitely has a problem. I visually saw coolant in the the #3 cylinder after I removed the spark plug. It only runs poorly at start up. I bought her a replacement motor but I haven't had time to replace it. It's been over a year and she just tops off the coolant and it drives around town fine for her.

    10. #8
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      Quote Originally Posted by Caspian3.2 View Post
      Hey that's not a very nice thing to say about Honda, Tmtalpey.

      Honda makes a great product and the resale prices are proof, not to mention, they have far less quality control issues than Volvo.

      Martaf, you could also ask your independent mechanic to perform a leak down test, which is different from a compression test. I think a leak down test gives indication on condition of the head but I can't remember for sure.
      Every car has their share of problems.

      A leak down test determines where compression is leaking (valves, rings or cooling system)

    11. #9
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      (2005 v50 AWD,T5, 97.6K miles) Thank you for all your helpful suggestions. You are convincing me to push for a little more diagnosis before I throw in the towel. So, I will take all the suggestions and go over them with the tech and see what he thinks and proposes.
      BTW: The codes it throws are : p0300 to p0305 and also 3100, 3110, 3120, 3130, 3140, 3150.
      I will also add that it has been my impression that the problem is much worse when the outside temperature is above 75F. But being, Houston, that's about 9 months of the year

      Please keep sharing any helpfull suggestions.

      PS. I will add that the car has never been over-heated; I have done all the routine maintenance/oil changes from day 1, it is not using up coolant or oil, and gas consumption is the same as it was 13 years ago (I keep a record).
      Last edited by martaf; 09-30-2018 at 08:57 AM.

    12. #10
      Global Moderator tmtalpey's Avatar
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      Those codes sure make it sound like a coil issue, and worse in hot weather, too. But coils can't cause low compression. Keep digging.

      It would be worth it to pull the Volvo DTCs instead of generic codes. Did any of your dealer visits do that? Did they tell you what they were (maybe on the invoice)?
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    13. #11
      Quote Originally Posted by tmtalpey View Post
      Those codes sure make it sound like a coil issue, and worse in hot weather, too. But coils can't cause low compression. Keep digging.

      It would be worth it to pull the Volvo DTCs instead of generic codes. Did any of your dealer visits do that? Did they tell you what they were (maybe on the invoice)?
      +1 On this. I literally had those codes (For Cyl 3) going home on Thursday and had to swap out a coil as it was going bad. Cleared it up. When I bought the car though ALL the coils had to be replaced because they were ALL misfiring under the last 60% of throttle and they were all the same codes as you have now.

      Also the low compression is still a concern so figuring that out is important. The other stuff should be pretty easy.
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    14. #12
      Global Moderator tmtalpey's Avatar
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      Ya know, now I think about it, a bum coil could have been causing a bum spark and therefore a dirty cylinder. A dirty cylinder also means a dirty valve, which might not seal properly.

      So, if your cylinder inspection indicates (only) a valve issue, and you do identify a bad coil, do the coil first!
      2005 V50 T5 AWD 6MT w/Heico tune, Heico exhaust, Bell intercooler, IPD TCV, Viva Forge CBV, Elevate rear swaybar and torque mount, Snabb shift kit, etc.
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    15. #13
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      Just so that I have some idea, can someone give me a rough estimate of parts and labor for rebuilding and installing a head.

    16. #14
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      You should determine if it's piston or valve leakage first. Replacing or rebuilding a working head could be ineffective.
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    17. #15
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      Quote Originally Posted by martaf View Post
      Just so that I have some idea, can someone give me a rough estimate of parts and labor for rebuilding and installing a head.
      Agree with the poster above that you'll want to make sure of what the issue is.

      For your reference though, I am replacing the head on my 2009 s40 now. The parts are costing me roughly $950. This includes:

      Rebuilt head: $600.
      Head gasket kit: $160
      Timing belt kit: $150
      Cylinder head bolts: $25

      I'm doing all of the install/removal labor myself, though. I imagine labor would probably double the cost (or more) depending on hourly costs in Houston. If you did the labor yourself, you'd also need to purchase some other tools as well for the job (or you could make your own depending on ability).

    18. #16
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      Thank you for your input. Quick update ....I know I always want to know what happened in the end
      After clearing the CEL on Saturday, I let the car sit overnight, and first thing Sunday morning took her through a drive cycle; let her sit all day and at 10 pm took her through a second drive cycle. The CEL never went on, and she ran very smoothly; did about 50 miles in total. Monday, I took her to get inspected, and she PASSED The temperature in Houston has been cool, and the CEL has yet to come on.

      So now, I am going to take her to the tech, and armed with all the information you have given me, I will discuss whether they can make a better diagnosis. I will also do the 95k service. If the weather stays cool and she continues to run as she has been, I will definitely keep her for a while.

      Will post when if I find out anything more.

    19. #17
      Global Moderator tmtalpey's Avatar
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      Coil (or coils). No type of cylinder or valve issue would resolve itself like this.

      But, do try to understand the compression difference.
      2005 V50 T5 AWD 6MT w/Heico tune, Heico exhaust, Bell intercooler, IPD TCV, Viva Forge CBV, Elevate rear swaybar and torque mount, Snabb shift kit, etc.
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    20. #18
      Global Moderator tmtalpey's Avatar
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      One other thing. If you are on the original timing belt, absolutely positively plan to replace it soon, along with its tensioner and idler pulley. It's >10 years and if you're keeping it, don't delay.
      2005 V50 T5 AWD 6MT w/Heico tune, Heico exhaust, Bell intercooler, IPD TCV, Viva Forge CBV, Elevate rear swaybar and torque mount, Snabb shift kit, etc.
      2016 XC60 T6 AWD
      1956 PV444 complete, running
      1956 PV444 very original, very rough

    21. #19
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      Thank you. The timing belt was replaced about 2 years ago. I have also tried to make the point with the tech about the fact that it seems weird that the issue comes and goes depending on the temperature. But they clearly think that I am a nut case and know nothing about cars. I may not, but I am a scientist and am observant and accurate.

    22. #20
      Global Moderator tmtalpey's Avatar
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      It's very easy to replace the coils in these cars, all you need are a Torx tool and a socket wrench. At this point, personally, I'd buy 5 and replace them all, given the evidence. MHO anyway.
      2005 V50 T5 AWD 6MT w/Heico tune, Heico exhaust, Bell intercooler, IPD TCV, Viva Forge CBV, Elevate rear swaybar and torque mount, Snabb shift kit, etc.
      2016 XC60 T6 AWD
      1956 PV444 complete, running
      1956 PV444 very original, very rough

    23. #21
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      Update:
      Took car in for 97.5k service and had long discussion with tech. Apparently when they were trying to troubleshoot the problem and found the compression problem, they did switch out the coils, but this didn't cure the problem.
      Agreed that doing a leak down test would be helpful, but worth doing only if I then go on to fix it, and in his opinion, it will not be less than $3600. So, he repeated his advice which was to just keep driving it as is. The strange thing is that the CEL has not come back on again, and you would never know it had a problem-runs perfectly......but the weather has been cooler.

    24. #22
      Global Moderator tmtalpey's Avatar
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      Quote Originally Posted by martaf View Post
      they did switch out the coils, but this didn't cure the problem.

      What exactly does this mean? Did they put in 5 new ones, then take them out and put back your old ones, in the same cylinders? Or do you now have 5 brand new coils?
      2005 V50 T5 AWD 6MT w/Heico tune, Heico exhaust, Bell intercooler, IPD TCV, Viva Forge CBV, Elevate rear swaybar and torque mount, Snabb shift kit, etc.
      2016 XC60 T6 AWD
      1956 PV444 complete, running
      1956 PV444 very original, very rough

    25. #23
      Quote Originally Posted by martaf View Post
      Update:
      Took car in for 97.5k service and had long discussion with tech. Apparently when they were trying to troubleshoot the problem and found the compression problem, they did switch out the coils, but this didn't cure the problem.
      Agreed that doing a leak down test would be helpful, but worth doing only if I then go on to fix it, and in his opinion, it will not be less than $3600. So, he repeated his advice which was to just keep driving it as is. The strange thing is that the CEL has not come back on again, and you would never know it had a problem-runs perfectly......but the weather has been cooler.
      #1 - the fact that the tech thought switching coils would help a lack of compression is utterly terrifying to me in the first place.
      #2 - If it is in fact a lack of compression caused by a bad spark, there are three options at this stage: The first is to figure out if it's intake or exhaust or a groove in the cylinder. Dirty firing means an excess of unburned fuel in the cylinder which in the case of my harley ran STUPIDLY rich (thanks PO, running it untuned for 64,000 miles) to the point of several MM of carbon on the piston crown and valves. The valves beat the carbon into the valve seals and some pieces that had broken off decided to rub lines into the cylinder liners, causing lower compression than normal, the valves still sealed perfectly fine with all that carbon displacing the metal but the cylinders were the issue. So that would be a good visual inspection to start out with. can rotate the crankshaft and check out the valves + seals too. Then you can TDC it and pressurize it with air and check and see if you hear hissing from either the intake or the exhaust. Either way I agree with the $3600 estimate. A lot of work needs to be done to something. Hopefully it's just the head and not the block. But starting small will give you the idea of what needs to be done.
      2006 Volvo S40 AWD T5 M66 - Dusty Rusty
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