The oil in the Escort had not been changed since August 8, 2006. You see, the car burns oil; since I was putting in a fresh quart every 100 miles, I didn't see the point of doing an actual oil change. The oil, I figured, was getting "changed" often enough.
But I got to thinking about it and realized a) that the oil filter should still be changed, damn it, and b) God alone knows what the hell was accumulating in the oil that didn't burn.
So I decided to change it; and for oil that was not more than 400 miles old it was some of the blackest shit I ever saw come from an engine. Now I'm glad I did it.
Anyway, I checked the #4 spark plug, wire-wheeled it, and stuck it back in, and then checked the #3 for giggles. The carbon on it was white, indicating very lean running.
"Well, doofus," I told myself, "think about it: the #4 cylinder burns oil, so the O2 sensor sees a 'rich' condition; the ECM commands 'full lean' in an effort to get the fuel-to-air ratio correct."
Of course this ends up having a negative effect on fuel economy: I must use more throttle to get the car to accelerate and it takes longer, thus increasing the total amount of fuel burned. Hence a car that should get 36 MPG only gets 34. (The one cylinder which burns oil doesn't help, of course, but here it actually turns out to cause the whole problem.)
It could either be rings or valve guides. The ideal way to test this is to perform a leakdown test: get that cylinder to bottom dead center with the valves closed, and then pressurize it with air, and listen for leaks. If you only hear a small amount of air escaping, the rings and valves are sealing well and the oil is coming from the top end.
But I thought I could do this: buy a gasket and cylinder head bolt kit, and swap the head from the known good engine to the red car's engine. Install new spark plugs, run for a month or so, and then check the plugs for carbon. If the #4 is only as gunked up as the other plugs (ie normal amount of carbon) then it's a cylinder head problem: get the head rebuilt and throw it onto the spare engine. If the #4 plug still gums up as bad, it's rings, and the entire motor needs a rebuild, which is beyond the scope of what I'm willing to dump into the car.
This method would definitively show what the problem is with the red car's engine, but I don't think it's a step I wish to take.
Oh, why would I need to buy a set of cylinder head bolts? The bolts are "one use" bolts. You see, the block is iron and the cylinder head is aluminum; to keep the head gasket from blowing they use special bolts which are made to stretch a certain amount, in a certain way, so that there is always a certain amount of pressure on the gasket, hot or cold.
This works very well; but unfortunately once the bolts have been used and removed, they're no good anymore--they can't be re-torqued to spec again--and need to be replaced.
The set doesn't cost much, so it's not a huge issue.
...and yes, I thought of going to a boneyard and getting a cylinder head from there. Problem: what if it's not any better than the one it's replacing? And one place said a cylinder head for a '95 Escort was $300, which is about what it would cost me to have the one I have rebuilt, anyway.
* * *
And so once I'd taken the car for a bit of a test drive, I came home and cut the grass. That didn't take very long, and when I was done, I came in and went to the fridge for a drink.
I was going to grab a jug of Pepsi, but then I thought, "No, I'll drink some of this here Gatorade."
...and I drank the entire freaking quart of the stuff. I wasn't even feeling particularly thirsty, yet glug glug glug down it went.
Good thing I wasn't thirsty.
* * *
Besides the oil and plugs, I also added some stop-leak stuff to the radiator (to see if that'll fix the leak--I'm guessing "no", but it's a $2 gamble, and if it works, it saves me $90 for a new radiator) and topped up the coolant. It took most of a gallon jug of the "50-50" stuff (pre-diluted) to do it. And I finally got around to replacing the cracked and dry-rotted breather hose. I'd had duct tape on the thing to hold it together, but I had a bit of hose the right size from the green car, so I swapped that out.
It's really just psychosomatic, but the car feels better now.