My mechanic just told me I have one of my six cylinders that has a compression rate of only 25. I am weeping as I continue to pay my car loan 
Can someone tell me if this can be repaired vs. putting in a replacement engine? I’ve been told this is a $4000.00 repair. Please help!
First, Are you having a particular problem that caused him to need to check the compression in the first place ?
To answer the ‘‘repair or replace’’ question requires a certain amount of labor invested in taking things apart to see if it’s a valve or rings issue.
yes, I was getting a tune up and the check engine light is on. He checked the compression and said that the one cylinder is bad.
Low compression can be a valve or head gasket problem. Get a leak down test to verify the actual problem.
Yes…find out why an engine of this late vintage is suffering from this condition. Could be a stuck valve…a burnt or broken valve…a damaged valve seat…head gasket issues…etc . I would seriously doubt its the piston rings…Unless this engine was severely abused via Late or NO oil changes that sort of thing… Methinks its a valve issue before anything else.
I use my compression tester with the gauge removed to test this. You rotate the engine until its on the COMPRESSION stroke of the affected cylinder… Then screw in the compression tester into the plug hole…and THEN…attach an air line to the other end of the testers line …the pressure needs to be regulated DOWN to about 15-20 psi… and then just let the air flow… If it rotates the engine…turn down the pressure so you can get the air to constantly flow… At that time you try to determine where the air is going…it will either go up the intake and out the throttle body…or it will go out the tailpipe… You can figure out which one with some diligence. I bet you get airflow out the tail pipe…and thus…find the bad exhaust valve or seat.
This would involve removing the head to repair the problem… Not that bad really.
I’ve gotten lucky a few times by removing the valve cover and finding excessive gap in one of the exhaust valves…I tapped the valve with a light hammer to free it up…and got it to bounce back properly to each of my hammer blows… after that…she ran perfect. I’ve found this condition on enough engines to mention it. So… Who knows.
Blackbird
What are the compression numbers on the other cylinders? If those are excellent then more than likely there is a valve issue on the low cylinder.
If so, you could probably get by with the repair of one cylinder head.
Are they saying 4 grand for another engine or 4 grand to fix the problem on one cylinder?