Dr. Jimbo

So I'm driving home Friday night and my engine all of a sudden starts misfiring, like I'm running on 3 cylinders. I was about 1 1/2 quart low on oil (this thing's been thirsty lately and I didn't realize how low it got). Topped it off and had it towed home and did a compression check today. Now I've had a check engine light on for quite a while (typical misfire codes) which I attribute to a leak between cylinders 1 and 2 as I found out with a leak-down test a while back . I'm not spewing any white smoke, but apparently there is a leak between the two cylinders. When I was pulling the spark plugs, there was a little oil in the #2 chamber where the coil pack sits and the #3 and #4 were full of oil (#4 being the worst). I did a compression check and got these #'s:

Cyl. 1=120
Cyl. 2=120
Cyl. 3=250
Cyl. 4=300

Now I realize that cylinder 1 and 2 are feeding into each other and I figured the high cylinder 4 # is due to the amount of oil that poured back into the combustion chamber after I pulled the spark plug out. I put the plugs back in and it's still misfiring (probably should have cleaned the coil packs with electrical cleaner before reinstalling them).

I've got 122k miles on the motor and I know that I need to pull the head and figure out the cylinder 1 and 2 leak. Anyone have any ideas on what's going on and why I would have such a proliferation of oil in the spark plug chambers/sleeves above the plugs? When I replaced the plugs and did a valve adjustment at 70k, I replaced all of the seals. Could a plugged PCV cause a build up of pressure under the valve cover and cause the oil to seep into the sleeves that the coil packs sit in? I can't imagine all of the seals failing at the same time. I guess a bad exhaust valve guide could lead to excess pressure under the valve cover too.

This one's got me scratchin' my head.

Looks like I'm driving the '91 Toyota pickup with 260k miles on the clock for a while.

realblag

There is no "excessive pressure" problem under your valve cover. Your tube seals are damaged and/or installed wrong.

Billman250

I second the tube seals, guaranteed.

You cylinders are not feeding each other. All you need to do is replace thew tube seals in the valve cover.

Your high comp readings are likely due to the excess oil that poured into the cylinder when you removed the spark plugs.

do this:

Remove VC, replace tube seals, remove spark plugs/coil packs and wipe all oil off, put it back together. Run it to three bars to burn off excess oil.

Then re-check your compression, you may find all your numbers even out.

Dr. Jimbo

Thanks for your input. Last year I kept throwing the CEL with cyl. 1 & 2 and random and multiple misfire codes. I did a leak down test and I had a major leak on cyl. 1 & 2. I listened for the hissing at the tail pipe and intake manifold. Nothing there. I heard it coming up from the spark plug tube. Testing cyl. 1, I heard the hissing coming from cyl. 2 spark plug tube and vice versa. I figured that there is a leak in the head gasket or a cracked head between #1 and #2. Not blowing any white clouds of smoke nor do I have chocolate milkshake coolant.

Dr. Jimbo

I found this on line regarding the leak down test:

Air escaping at the following locations indicates a potential problem:

1. Oil dipstick tube indicates pressure escaping from the cylinder into the oil jacket. This usually indicates stuck, burned or worn rings or cylinder walls.

2. Radiator filler opening bubbles or sound indicates pressure escaping into the coolant jacket. This can indicate cracked cylinder walls or damaged head gasket. In case of a damaged head gasket, often two or more adjacent cylinders will show the same problem.

3. Adjacent cylinder indicates a damaged head gasket.

4. Tail pipe indicates burned, stuck or worn exhaust valve.

5. Carburetor or fuel injector intake indicates stuck, burned or worn intake valve.

Dr. Jimbo

So I got new spark plug tube seals and put them in yesterday. The old ones looked fine. No cracks or splits. They were installed correctly and not inverted. Cleaned everything up with Electro-Cleaner. PCV was plugged, so I cleaned it up and it rattles now. Plugs look good. The S is still firing on 3 cylinders. I think I might have fried a coil pack when it was drenched in the oil. I get the same misfire codes I did before but now the CEL is flashing as it was when it started running on 3 cylinders.

Doing a google search on this, I didn't realize how many other S owners have had the oil leak into the spark plug tube. I thought it was so random that no one else would have had that problem, so my apologies about not searching before I posted.