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Old 06-23-2009, 03:50 PM
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Low Compression

I got a '94 Saturn SL2 sitting around with no purpose in life. The only major issue - it has very low compression across all cylinders, other then that I dont think there are any problems with the car. What could be the cause? I am thinking bout either fixin it up or selling it, but before fixing it wanna try to see if its even worth the effort. Any likely reasons? (preferably fairly easy fixes) I originally thought it may just be a head gasket... what else could it be?

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Old 06-23-2009, 07:34 PM
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"very low compression across all cylinders"

There are two components that have to seal up to make a motor valid, valves and piston rings. Neither is a "fairly easy fix".

The cheapest fix may be to transplant another motor from the boneyard. Find a good compression, low mileage motor and swap it out yourself. I'd consider a swap in either case, whether you plan to keep it or to sell it.
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Old 06-23-2009, 07:45 PM
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How many miles are on it and has it been sitting? Squirt some oil into the cylinders and see if that will make a difference. If it has been sitting a long time, the cylinders made be dry as a bone and that can make a difference. Does it run at all?
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Old 06-23-2009, 08:39 PM
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What PSI to you is considered "Low compression"??
Have you looked it up? I wouldn`t think the compression ratio of this engine to be particularly great. Give each cylinder a shot of marvel mystery oil and let sit over night. Then redo your compression check with the throttle set at wide open and all the plugs out.
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Old 06-24-2009, 08:56 AM
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gages can be wrong. try with another gage.

the chances that all 4 cylinder have the same "low compression" from bad valves and rings is very low. Typically 1 or 2 will be low, but not all 4.

a timing chain with retarded timing will reduce cranking pressure on all cylinders.
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Old 06-24-2009, 05:16 PM
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The first thing I would do is pull the top of the timing cover off. There is a good chance that the timing chain slipped a tooth which would cause low cranking compression. See if all your timing marks line up. The tensioners are a common failure point in the 1.9 letting it slack enough that it jumps a tooth
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Old 06-25-2009, 05:37 PM
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Ok I will try... Thanks guys. Gives me something to do this weekend...

IF I am going to need to change the engine (or just decide to... cause 140 HP sounds so much better then the lame not 120 the Saturn got.), I got a KA24DE from a 2.4 L Altima . Would that fit, and work, or other components need to be changed too?

And, yes, the car does run. However it seems to have no power, really rough idle, and is louder then a jet. Which, as far as I remember would indicate low compression, if I am correct? Also, there is a buncha oil on the block, around where the gasket is.

Its got 186K miles on it and has not been driven for just over a month now.

Oh, and also, it has barely passed smog when it was still driven, near 2 months ago, if that has anything to do with it.

As for the compression, a mechanic checked it out. I think he is an idiot... I do not remember the numbers, but he said something along the lines of 100 and some psi as opposed to damn near 200 it is supposed to be at... If that was to be true, would the car even run...? and 200 psi sounds like a bit too much for this car.
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Old 06-25-2009, 05:53 PM
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a car like that should have like 150 PSI max.. I don't have books on saturns, but I'd guess, 135 PSI across all cylinders would be good
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