[gjgerhard]

I just learned something the hard way and I'm making an effort to tell people about it.

A little background: I bought my Honda Civic FE new in 1983 (the "FE" stands for "Fuel Efficient"). I have achieved over 50mpg in normal commuting. However, one of my techniques is what's called "forced stop," if I understand it correctly. I routinely switch off the engine when going down hill.

Just about everyone maintains that doing this is dangerous, but I take the arrogant position that it is dangerous for people who don't know what they are doing. The most obvious issue here is the steering lock. Cars have steering locks to prevent theft. I disabled mine so that it would not be a threat. Steering can get harder if the car has power steering. My little Civic does not. Yes, the brake booster looses effectiveness, but I have the ability to push the pedal as hard as it needs. This technique is for manual shift only. I always switch the ignition back on as soon as the engine stops and leave the transmission in the appropriate gear with the clutch depressed. Note that riding the clutch with the engine running will wear out your throw-out bearing, but has no effect at all when the crank has stopped.

However, I discovered that switching off the engine while in traffic can damage it, which is what happened to me. Twice.

Here's why: there are two ways to stop an engine that's not a diesel: you can switch off the ignition; you can shut off the fuel. If I ever go back to doing this, it will use the second method. What I was doing, and what caused the damage, is I would be driving along at elevated rpms, I would depress the clutch and switch off the ignition, and wait for the engine to stop turning.

While the engine is spinning down to stop, it continues to ingest a fuel/air mixture in the cylinder that is not getting burnt. Gasoline is horrible as a lubricant, and is actually quite effective for washing lubricants away. So what I was doing was washing away the thin layer of oil in my engine's cylinders, and eventually the rings started to complain.

The symptoms of this damage are a little unusual. What I first noticed was a small cloud of oil smoke when I leave a stoplight (having idled a bit). Once up to speed, there is no apparent smoke. Oil consumption is not radically up. There is no smoke when starting cold.

My son has a 1983 Civic, too. I rebuilt both of these engines recently; mine is bored .020 over, his got new pistons. I was driving his car while mine was in the shop getting painted, using my usual techniques. It developed the symptoms I described, except that his got so bad that it was fouling plugs.

I got my car back and it was only a couple of weeks before it started smoking, too. That was enough to convince me that my switching off the engine at medium revs was the culprit. Note that switching off an engine normally occurs while the thing is idling, so the potential to create problems is much reduced.

It is likely that making sure the engine is idling before switching it off would prevent the kind of damage I have encountered, but I'm just going to leave it idling from now on. If you use this technique and have a way to shut off the fuel, use that. I hope this will save somebody out there from ruining his rings, for what it's worth.

Greg in Seattle