I need some help. I am new on here and didnt know where to go. My 1990 chevy k1500 5.7 V8 isnt firing on numbers 3 and 4. I know it has a gas leak and it does drive just fine. It shoots gas out of the left pipe on the exaust. By the way its got dual exhaust on it. My guess is the spark isnt hitting on 3 and 4. The truck has 170,000 miles and is super clean. except for a little rust on the bottom. Any help is a apreciated.
i am gonna try to test the wires and plugs but just lookin for ideas.
Justin

 

? Drives fine on 6 cylinders? If you have gas coming out of the exhaust, I'd say you have a stuck or burned intake valve. Pull the spark plugs on those two, with a small borescope look at the valve faces/seats.

 

I heard it might be a stuck valve. I was hoping it wasn't, but that usually my luck. I dont have a borescope on hand but i will try that. thanks for the help.

 

And yes it drives fine on 6 cylinders. If you listen to the exhaust it sounds like it skips or the timing is off but besides that, it drives great. It's a chevy though what can I say. I am sure it would do fine on 3 cylinders to Ha.

 

I jus pulled spark plugs and they have oil on them. I am hoping its not a bad gasket or ring.
will a stuck valve cause that? I gotta have it fixed before the 20th. Should i replace it or just try to unstick the valve.

 

Compression test the cylinders. Record the psi for each cylinder. This will give you an idea of what you are looking at.

Have you pulled the valve covers and looked at the rocker arms? Is there oil sludge build up? Are the rocker arms moving in their full range of motion (remove spark plugs and have someone crank the engine)?

 

so it was only one that had oil. I didn’t get around to the rest due to time. I ran a compression test on the first 2 cylinders.

quick question do you remove all plugs and then check each one or does the engine need to run to check it. I ran it and checked it so don’t know if it’s accurate. I appreciate the help.

 

I didn’t not check the valves yet but will do that.

Thanks

 

Pull all plugs, squirt a tiny bit of engine oil in the cylinder. Test all 8, record what they are.

 

thanks will do