I just picked up my second Protege, a 97 LX. The engine code is "P0304 - Cylinder 4 Misfire". Compression check shows 95psi on #4 and 150psi on1-3. This 5-speed has 108k and is in very good condition.

I've put about 300 miles on it and the oil is clean (no water), the original plugs are clean and the radiator does not indicate any oil residue.

What is the best way to determine if the head orthe rings are the problem? My dad used to talk about squirting motor oil in the cylinder to seal the rings just before the next compression check to see if the pressure jumps a little - if a significant jump, this would point at the rings.

Thoughts?

 

Hi -possible there arevalve with wrondadjustment\\
we were runningan air thru spark plug holes
put cylinder at Firing Posandhook up hose
- if air goes thru valves - bad valve
if doesn - Ring
Got it?

 

odds are that if the compression is low and the oil is clean, you are looking at either a bad ring or just a bad hone on the cylinder. there is the possibility of a bad valve, so do the above test before you rip anything apart. remember, any time that you swap out rings, it is always a good idea to re-hone the cylinders.

 

update: I pulled the head and had it cleaned, planed flatand vacuum checked, checked good. no scoring in the cylinders but a distinctly darker tint to the staining on the piston crown. popped them out and dropped the rings in the bad cylinder, gap is withing spec at .012" at upper and lower locations.the block deck checked flat too.I noticed a discoloration on the cylinder walls in #3 and #4 about 2 1/2" down. thinking it was a casting flaw, I dye checked and got an oh-so-faint indication in #4 only. it was repeatable. I rehoned the cylinders and re-dye checked, nothing shows. reassembled with new gaskets, compression still at 90 on #4 and 125 on #3, so no change.

bought a Jap used import engine and installed it to get back on the road, but I'm planning to figure this one out. next is to have the block bored oversize to true the cylinders. if there is a flaw in the block, it should reveal itself during machining.I'll also reseat the valves andput some dye check on it too.

what else could it be?

 

just go ahead with boring the cylinder. you will need new pistons then, but that will eliminate the problem if it is amplified by the piston. other than that, i don't know what to say. there aren't a lot of other things that could cause that.