Low compression on no. 4 and 6 cyl's. Miss at idle. What would be the cause for this ? Engine has 150K miles. Previous owner says it is loading up with gas in cylinders? Could this be a blown head gasket on the passenger side bank ?

 

My first guess when two adjacent cylinders have low compression is a blown head gasket between the two.

 

That was my first thought. It was a blown head gasket on that bank. I had the new truck taken by Roll back to a garage. I am waiting to hear my mechanic's diagnosis on this. He works on vehicles on weekends. I can't wait to hear whether it is a problem that is 'repairable in the truck'---such as a blown head gasket or a burned valve----- or a new engine is going to be required. Waiting is excruciating.

 

Many moons ago, I had a K5 Blazer that blew the head gasket between two of the cylinders. Being young and dumb, I drove it about 50 miles that way before I could get to someplace that was safe to leave it overnight. When I took the head off, I saw that it has actually eroded the metal on both the head and the block, leaving a pretty significant groove in each. I had to tear down the whole engine so they could be welded up and re-machined. Hopefully, you don't have anything like that.

 

I am still thinking the problem with the low compression on cylinders no. 4 and 6 are a blown head gasket on that bank. To those with personal experience or personal knowledge about the 4.3 L V6, when you do a head gasket change out , do you just change the head gasket on the damaged side---bank no. 2, 4, and 6----or do you go ahead and replace both cyl. head gaskets ? What is the standard operating procedure ? When you do this tear down, what other things should you do while you are in this deep into the engine ? Since this is a 2003, it came from the factory with the new improved fuel injection spider set up. But how about the fuel regulator and other items hidden under the intake manifold ? Anything like that that needs to be looked at and replaced during this procedure? Some might say its a great time to do a valve job....on both cyl. heads. That would require removing both heads and replacing both gaskets.

 

Plan A was to sell my Blazer back to the insurance company, buy a 2003 Pick up, and have a guy with a backyard shop repair the pick-up engine. That engine had low compression on cylinders no. 4 and no 6. Sounded like a blown head gasket, right? Now the big and very bad news is the pick-up engine is 'burned up' and can't be repaired. Apparently the former owner ran the pick up when it was overheated. As a result, the engine was damaged severely. Suddenly I need a new engine quickly. I decided to put the engine out of my 2003 Blazer in it. I then got the Blazer back as a 'salvage' deal and therefore lost $500--insurance policy-- but got a 'known good engine'. Now all I have to do is to transport my Blazer to the mechanic's new shop in the country. Plan B is he will pull out the bad engine in the Pick-up and swap in the good Blazer engine with only 123, 850 miles all on full synthetic oil and the best oil filters available. Therefore, the outcome is the insurance will give me only $1750 for salvage of my old Blazer. I will have the engine and trans. pulled and then sell the rest of the body to a salvage yard. I have no idea what I will get for the wrecked shell minus the engine and trans. I also will incur 'roll back tow expenses' moving the Blazer to the shop and then later to the salvage yard for the final destination. This is my first experience with any auto insurance company and it has been an eye opener. If anyone has any advice on the best way to get through this maze of red tape and insurance procedures, PLEASE let me know. I would appreciate your help and advice. TIA, Jim

 

How does he know it is " burned up"? You are talking about a lot of labor to pull 2 drivetrains and reinstall 1. I bought a '97 4.3 not long ago with 110k miles that had a miss on #6. Guy threw the parts cannon on it. I had a feeling it was a bad valve. Did a leak down on all cylinders and #6 had almost 100% leak down and #4 had an amount that a misfire should of been picked up on the scanner. Grabbed another set of heads from a friend, re-gasketed the motor, popped out the freeze plugs and cleaned out the block, and has ran great.