Working on my 92lx coupe 5spd, bought it with a miss fire. did the usual, tune up, swap injectors, still acted the same. so i pulled the head off thinking i had a burnt valve (even though the head has recently been rebuilt from a snapped timing belt per the previous owner) and noticed some odd things in my block, cylinder 4 has some odd scoring, and the honing cross hatch is far more visible than in cylinders 1-3, which are pretty smooth. car has 236k miles on it... i also noticed the head has two different kinds of exhaust valves?

here's some pix, i'm disassembling this little by little each day.

head:


cylinder 4:


other cylinders:

 

I should add i have not cleaned the egr ports yet as i bought a f22a6 intake manifold, cam, and ecu from the jy and was going to clean that up and install it. If it turns out my block is bad or my head atleast um just going to get an f22b1 and swap it

 

did you test compression? get the right valves.

 

Ya, I woulda compression tested it before pulling the head. You could get a set of precision straight edges and check for warpage. That cylinder is prolly dead.

 

Yes i did actually i got an average of 125psi in 1-3 and 115 in cylinder 4. Car was as warm as i could make it wout driving it before i stopped breathing due to the exhaust being so stinky. Drove fine home minus the miss at idle just has bad tags

 

any one have any idea why the physical condition of cylinder 4 looks different?

and honestly, should i source another head?

 

sounds like your piston rings is about to go look for smoke. at first i thought my valve seals was gone cause of misfire and oil in exhaust port but i replaced and i had the same problem so that left the piston rings. tore it done and all 4 walls were scared but 3 n 4 the most.

 

It's likely the piston rings are bad if you are sure the compression test is good.

115 psi isn't something to be highly esteemed. I would swap out the engine for a jdm f22a

 

I have the same problem, #4 cylinder is running richer than the other 3. Over time it looks like that took a toll on the cylinder walls.

I'm thinking of having my injectors flow checked.