Compression problems on a 2001 ls v8?

[highmiles]

Hey, I'd hate to start a new thread but I haven't been able to find much information in any of the other ones. I have a 2001 Lincoln ls v8. the car does have 292,000 kms. that being said the other day I was driving it and noticed it started dumping blue smoke out the exhaust.
a code check said 3 cylinders were miss firing and 3 ig. coils were off to but i had just replaced all 8 coils and changed the oil when i got the car.
I think I've narrowed it down to a piston ring problem and found a few cylinders around the 40-50psi range.

Does anyone know what the reading should be on a perfect running ls and if you can drop the pistons out of the bottom? as well as anything else i could look into?
I realize its a high mileage car but id really like to get this running well again as ive had it for less then a month :L

 

[joegr]

The minimum is 100 PSI, but it should be higher. Ideally, all compression readings should be within 10% of each other, but they must be within 25% of each other if you want it to run right.

 

[04_Sport_LS]

Are all of the cylinders that are reading low compression, the same ones that showed a misfire? Are all of these cylinders on the same bank, (head)? If so, you may have had a cam chain slip, and one, or both of the camshafts on that bank have jumped time. This seems to be a common issue with these engines. Especially 2000-2002. I don't have the actual spec in front of me, but most, (not all), engines today run 160-180 psi per cylinder. I'd guess the 3.9 runs closr to 190-200 psi. Google for the cylinder compression on this engine, and you will probably find your spec. Someone else may chime in too, that knows more than I.

 

[highmiles]

The lowest two were cylinder 4 and 8 running at 40-45psi. I changed the spark plugs as they were brutally old and upon start up the exhaust seems to be running extremely rich. I think the piston problem is just small leaks due to the highmileage so I'm going to try one of those engine restore oil additives and look into problems with the fuel system. Thanks for the good info I was unable to find anything on google for these cars other then people selling parts.

 

[SteveSC]

No amount of engine treatment is going to fix 40 to 45psi compression. You are wasting your time. Either the timing chain jumped or you have other issues. I suspect the tensioner let the chain slip and you have improper timing on the valves. It is also possible the chain slipped enough for the pistons to have hit the valves and bent them. You need to take the engine cover off and check the alignment. If you're lucky you will just need to replace the tensioners and set the timing chain up. If you are unlucky you will need a moajor engine overhaul. I would suggest just replacing the engine with a used one as a rebuild will be much more expensive.

 

[hite337]

40-45 psi on cylinders that aren't next to each other means the piston rings are bad on those cylinders . If they are next to eachother it would probly be a bad head gasket. Mine sits at 185-200 psi on all cylinders.

 

[scjmc]

You can pour engine oil onto the piston through the spark plug hole. Check the compression again and if it improves piston rings are probably the culprit. If it does not improve then it is probably valve train related.

 

[hite337]

You can pour engine oil onto the piston through the spark plug hole. Check the compression again and if it improves piston rings are probably the culprit. If it does not improve then it is probably valve train related.

I forgot to say that too. Good info

 

[scjmc]

hite337 I guess you are right too. If it is valve train all four cylinders in that bank would be low.

 

[Telco]

hite337 I guess you are right too. If it is valve train all four cylinders in that bank would be low.

Individual valves can fail to seal on their own for whatever reason. If all four cylinders were low it might point towards a cam/timing issue, but if even one cylinder has good pressure then it would be a valve, valve seat or valve seal issue.