Just bought a 95 legacy sedan 5spd for cheap. everything works good on it except it runs on 3 cylinders. He says it started about 5 months ago and hasn't driven it much since. Its coming from the passenger side closest to the firewall. I took the plugs out and that one is all wet and looks like it doesn't fire at all. Judging from the gas appearing on the exhaust pipe the injector is at least firing, not sure if its clogged, or what. He said he replaced all the plugs, plug wires, fuel filter, air filter.

 

It basically runs on 3 cylinders as it shakes and sputters like its down one. I should probably go buy a compression gauge. What are the different possibilities of what it could be?

You need air, compression, fuel and spark to make it go bang.

 

Odds are it has no compression. Since subarus dont loose compression to rings often, I am going to say its a burned valve.

 

 

nipper

????? i would see of you are getting spark at that cylinder. just take out the plug and set it on metal to see the spark. you may have an issue withthe coil pack.

 

make sure you dont have spark before suspecting a burnt valve ?????

 

You need air, compression, fuel and spark to make it go bang.

 

Odds are it has no compression. Since subarus dont loose compression to rings often, I am going to say its a burned valve.

 

 

nipper

It's a wasted spark coil so you have to lose a whole bank - you can't lose just one cylinder with a wasted spark coil pack.

 

Run a compression test.

 

GD

It's a wasted spark coil so you have to lose a whole bank - you can't lose just one cylinder with a wasted spark coil pack.

 

Run a compression test.

 

GD

 

 

What he said.

 

i just took an educated guess

????? i would see of you are getting spark at that cylinder. just take out the plug and set it on metal to see the spark. you may have an issue withthe coil pack.

 

make sure you dont have spark before suspecting a burnt valve ?????

 

 

I pulled the leads off the coil one at a time while it was running. The cylinder in question didn't arc like the other 3. I tried a plug wire from another '95 subaru I have and that didn't help. I'm guessing its not getting spark because the plug is gas soaked from not firing? I pulled the plug out and it looks like it hasn't fired at all, looks brand new other than gas all over it.

 

So could a bad exhaust valve cause it not to fire, then in turn cause the plug to get wet from gas and not fire?

So could a bad exhaust valve cause it not to fire, then in turn cause the plug to get wet from gas and not fire?

 

 

I don't think so. Pull plug wire off existing spark plug. Attach another spark plug to end of plug wire, then ground it out, and see if that plug fires with good spark. I am thinking your problem is spark, not fuel, or exhaust valve.

 

Still, a good idea to run a compression test on that cylinder to learn if valves are okay.

so what is the long term effect of a working injector and a non firing plug???

so what is the long term effect of a working injector and a non firing plug???

 

A lot of gasoline in the oil and down the exhaust pipe!

A lot of gasoline in the oil and down the exhaust pipe!

 

Prolly a good idea to change the oil and oil filter, because it is contaminated with raw gas. The diluted oil is a bad lubricant for the engine. It doesn't happen often, but I have heard of gas fumes in the oil pan exploding, because of unburned gas droplets draining down into the oil pan, resulting from a misfiring plug.

just measured compression at 155 in the cylinder that's dead. I'll move a coil pack from another 95 I have and see if it works

Edited December 21, 200916 yr by destey

A lot of gasoline in the oil and down the exhaust pipe!

 

 

And a very pissed off catalytic converter.

 

 

nipper

The lack of spark could be a hairline crack inside the coil causing high resistance to that plug. Pretty common on old GM coil packs.

If you have a known good coil pack swap it in and see if it fixes it.

If that fails pull the spark plug out and wait a day or so to let that cylinder air out. Turn the key to the ON position to pressurize the fuel lines then smell/listen around the spark plug hole for gas fumes or a hissing sound from the injector being stuck open.

so what is the long term effect of a working injector and a non firing plug???

 

Fuel wash that can chew up the rings, thin out the oil leading to poor lubrication of bearings/other moving parts, burn out the cat. Fun stuff!

swapped in a the coil and it worked good as new! thx for advice guys. I also changed the oil, mixed with gas