1 cylinder low compression
12-06-2008, 09:19 PM
#1
1 cylinder low compression I was wondering what some of you guys thoughts are on this.
If all cylinders are 170psi and one cylinder is 80psi do you think the car could still run good?
Right now the car is misfiring like a ****, popping, shaking, skipping, the whole nine yards.
I know that it must be fixed but what I dont know is if something else could be causing it to run like that?
It already has new plugs and wires and the EGR is working fine.
Im going to fix whatever is causing the low compression in the cylinder but Im not 100% sure that there is not something else causing the way it just started running. Car was just idling at a traffic light when it started doing this.
If all cylinders are 170psi and one cylinder is 80psi do you think the car could still run good?
Right now the car is misfiring like a ****, popping, shaking, skipping, the whole nine yards.
I know that it must be fixed but what I dont know is if something else could be causing it to run like that?
It already has new plugs and wires and the EGR is working fine.
Im going to fix whatever is causing the low compression in the cylinder but Im not 100% sure that there is not something else causing the way it just started running. Car was just idling at a traffic light when it started doing this.
12-07-2008, 12:23 AM
#7
Well tomorrow Im going to squirt some oil in the cylinder and retest to see if it goes up. If it does that should prove its rings, but since every cylinder except that one is fine Im betting its not rings.
Im thinking its a sealing issue with the valve or head gasket. I dont have a leakdown tester but I can get one. Im guessing I need to check that cylinder on the compression stroke with the leakdown tester to determine where the leakage is.
The fact that the adjacent cylinders are fine and there is no evidence of water in the oil and no pressure building in the radiator leads me to believe its not the head gasket.
I know there is a problem but what I want to know is if the car "could" run fine with it like that. Could that cylinder have been like that for a while and the issues it has now be something else?
Im thinking its a sealing issue with the valve or head gasket. I dont have a leakdown tester but I can get one. Im guessing I need to check that cylinder on the compression stroke with the leakdown tester to determine where the leakage is.
The fact that the adjacent cylinders are fine and there is no evidence of water in the oil and no pressure building in the radiator leads me to believe its not the head gasket.
I know there is a problem but what I want to know is if the car "could" run fine with it like that. Could that cylinder have been like that for a while and the issues it has now be something else?
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12-07-2008, 05:11 PM
#8
Launching!
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you have to have a min of 90 psi for combustion to occur. being below 90 makes me thank about other eng damage. if it is rings than how bad are you destroying the cyl wall/piston. i woudl find the problem before any more damage takes place.
12-07-2008, 05:45 PM
#10
the popping you mentioned makes me think its a valve.
you do not have too have a leak down tester.
remove the valve cover,rockers on that side pull the push rods on the bad cyl.
take a hard look at the springs and the other parts you removed. if you do not see the smoking gun use your compression gauge adapter to put compressed air in the cylinder
and find the air leak eg: TB, exhuast, oil fill cap.
you do not have too have a leak down tester.
remove the valve cover,rockers on that side pull the push rods on the bad cyl.
take a hard look at the springs and the other parts you removed. if you do not see the smoking gun use your compression gauge adapter to put compressed air in the cylinder
and find the air leak eg: TB, exhuast, oil fill cap.
12-08-2008, 12:21 AM
#11
wrencher
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Wow you can guess at it all day could be this could be that, do a leak down & you'll know. 
http://www.carcraft.com/techarticles...ter/index.html
http://en.wikipedia.org/wiki/Leak-down_tester
You can even just use a compression tester 'whip' with the schrader valve pulled out. Then induce air from a compressor w/ the valves closed 7 see where the air is escaping the cylinder.
It should be pretty obvious where w/ it @80psi cranking compression.
You can even do a running compression on it it will tell you the volumetric efficiency of that cylinder. It should do about half of the regular cranking compression @ idle. If not it's usually valve train related.
Cheap @$$ compression testers not real good for pinpoint testing BTW.
http://www.carcraft.com/techarticles...ter/index.html
http://en.wikipedia.org/wiki/Leak-down_tester
You can even just use a compression tester 'whip' with the schrader valve pulled out. Then induce air from a compressor w/ the valves closed 7 see where the air is escaping the cylinder.
It should be pretty obvious where w/ it @80psi cranking compression.
You can even do a running compression on it it will tell you the volumetric efficiency of that cylinder. It should do about half of the regular cranking compression @ idle. If not it's usually valve train related.
Cheap @$$ compression testers not real good for pinpoint testing BTW.
12-08-2008, 10:29 AM
#12
Yep a leak down will tell you everything you need to know. which valve int or ex. Or if its a ringland. Or you can go ahead and do what your going to have to anyways and pull the motor. That cylinder will have to be fixed so no need and beating around the bush about it.
