Did a thing and got pleasantly surprised but I'm trying to understand why.

I while back, right after I first bought the civic, I did a compression check. The numbers were a hair low but nothing out of the ordinary for an engine with nearly 230K on it. Cyl 1-152. 2-160. 3-165 4-155. Cyl two and three were a little higher due to a leaky valve cover gasket that filled up the spark plug holes with oil, essentially making those wet measurements.

Last week on a whim I bought a can of Engine Restore for it. It feels like a totally different car now. It's quieter but the biggest difference is in the idle quality. The thing has never had a nice even idle. Prior to the Restore it was very rough.

Pull up to a red light and it'd roughly idle somewhere between 5-10 seconds, then it'd have a big stumble, and really shake for a second or so then roughly idle steady for another 5-10 seconds and repeat until the light turns green. It would shake the steering wheel badly and the stupid wink rearview mirror was just a blur.

After the Engine Restore I almost can't even tell it's running. The steering wheel doesn't shake and the mirror only has a very slight vibration in it. I can actually see out of it. The stumble is still there but it's very subdued now.

So I'm happy about that but I got to wondering why. What could the Engine Restore have done to cause this?

Previous to the Engine restore, in an effort to help the idle issue I've checked everything for vacuum leaks, set the idle speed correctly per the FSM and attempted to set the timing. I have not been able to set the timing but it's only slightly advanced. I followed the FSM and many different techniques found online but nothing I have done makes any difference to the actual timing. I can turn the distributor all the way advanced or retarded and it makes no difference to the timing marks on the crank. Damned if I know. Unless my timing gun has stopped working correctly.

Anyway what could the Engine Restore done to so dramatically improve the idle quality?

What's in the kit?

Most engines will build up intake and injector deposits that will really alter the idle quality... But that would work if a big part of the kit was in the fuel.

In reply to alfadriver:

No, Engine Restore the oil additive. You know, the snake oil stuff.

Interesting.

Your wet numbers were giving you much higher readings than you realized. The restore sealed up some of the leaks and helped bring up the two cylinders to something closer to normal.

I have used that product in the past to by more time till I re built the motor and I found scratches in the cylinder walls that appeared to be filled in. I also found scratches in bearings that were filled in.

alfadriver wrote: Interesting.

Yeah, that's what I thought.

The product is made to increase compression by filling scratches and groves in the cylinder walls. That's really all they say it will do.

Given my compression readings and compensating for the two wet readings I don't see why or how using this product so dramatically improved idle quality.

I'm going to recheck the compression after around 1K miles as that's how long they say it will take to be in full effect.

But it was an immediate, night and day difference, and that's what I'm trying to figure out.

In reply to dean1484:

That's certainly a possibility. I didn't do actual wet readings as I didn't really have reliable dry readings.