Pug 306 low compression in one cyl

dougguk

dougguk

dougguk

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Joined
7 Mar 2006
Posts
136
Hi everyone

I'm having a problem with my 306 xsi P reg(97). The car was running fine and all the sudden started running like a pig over night. The car lost its normal power and seem to be really struggling when accelerating kinda sounding like it was missing a heart as it jumps abit when accelerating.

I'm a complete amateur when it comes to cars. But after doing some trouble shooting with a friend I came to the conclusion that the car could be on running on 3 cylinders. I change the spark plugs but this didn’t change anything, Also changed all the leads still no change. Using a timing tool it seemed that cylinder 2 wasn’t firing which I then thought it could be the Ignition coil. After replacing this still had the same problem. From what i have been told and heard it does sound like the car is running on 3 cylinders but this should be caused by an electric fault.

I have had a compression test done and it seems that cylinder two has 5psi where the rest have 10. Could be down to a cracked piston ring or faulty cylinder I believe.

Is there anything else that could be causing this problem or anything I have missed. Please please any suggestion would be great
 
For someone who says they are noob with cars you seem to know your way around an engine and where to source parts for it. If you still can't fix it take it to a garage, with the expense you have gone to with extra bits and bobs you have bought it wouldn't exactly be expensive to take it to a mechanic.
 
Squirt some oil into the cylinder, do the compression test (even 10psi sounds incredibly low, but I could well be wrong) again. If it increases then it sounds like a piston ring, if it stays the same then look at the valves.

Edit - Yeah, 10psi is way, way too low. You should be getting around 180psi I believe. Also check the head gasket.
 
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Failing that, it could well be that the head gasket has blown. What mileage has the car currently got? Check for the usual signs PLUS get the engine upto running temperature with the radiator cap off and try and spot if any air bubbles come out.

If its not the headgasket, something else is worn / damaged! As you're probably aware a cylinder shouldnt have low compression for no reason... Its not consumables that cause a low compression either :(
 
He probably means 5 and 10 bar. This would make sense.

Sounds like either a valve or piston ring issue. Try a wet and dry comp test and see if there is any difference. Is it burning oil?
 
The only reason i sound like i know a lot is because of a friend showing me all the bits and piece's while trouble shooting(i dont know anything else really other then what i have posted :D ). I think thats right about the pressure gauge being on 10 bar on 3 of the cyclinders and only 5 on one of them. Its a bit worrying if thats low on all of them :eek:

Its been a real pain as the car was so nice really great to drive havent had it long and this happened. I'm not sure how much its gonna cost to fix any ideals :confused:
 
ci_newman said:
Failing that, it could well be that the head gasket has blown. What mileage has the car currently got? Check for the usual signs PLUS get the engine upto running temperature with the radiator cap off and try and spot if any air bubbles come out.

If its not the headgasket, something else is worn / damaged! As you're probably aware a cylinder shouldnt have low compression for no reason... Its not consumables that cause a low compression either :(
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The cars done 100k cambelt changed at 80k. Service history is full but is needing a service now. But i dont think that a service would change anything like that :p. It just driving me crazy the fact the car was fine and then this happened. I guessing that it could just be sod's law at the end of the day.

If the headgasket has gone wouldnt i notice like a grey colour in the oil as the oil in the car is fine. Any thing else it could be. cheers for the help so far
 
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