Oscillating sensor plate

[jjeffries]

Tony, you are one of the good guys. John in CT.

[gazzerr]

Wow Tony - that's awesome!

[ninelevenick]

There's a little metal dome shaped piece at the very top of the main bore that somehow gets damaged and dimpled. You should be able to see the top of that piece, and the dimple by looking through the center port that goes to the WUR. With a light source. Rather inaccessible for repair.

I took a look in that bore this evening. I didn't see any dimples.

[ninelevenick]

Another observation I made yesterday while I had the car running: when the sensor plate is doing its fluttering/oscillating thing, I pull down on the arm a bit, and the idle drops and steadies without the backfires. Now, if I unscrew the oil cap, the engine idle drops even more, but the sensor plate starts to flutter again after a few seconds. I cannot explain why it does this. It's interesting though because I really do not notice a change in idle when I pull the oil cap otherwise. I'm removing the FD tomorrow to investigate more.

[allaircooled]

I could be wrong but if you pull down on the arm, you are decreasing the amount of fuel to the injectors. Maybe you are running rich still, along with the oscillating sensor plate problem.

[ninelevenick]

When I push down a bit, it's as if the plate should be in that position.

I pulled the FD. Mr. Walker mentions a dimple on the top. The photo I took is bad, but there appears to be a little mushrooming on the very top of the bore. I'm not sure if this is the dimple that he refers to.

[ninelevenick]

I got the car running well today! The plunger moved freely in the chamber, but I liberally sprayed carb cleaner in the FD anyway. I installed the FD and fired up the engine. It ran backfire free during the cold start, but backfiring continued within ninety seconds after start. I played around with the mixture a bit. First I went lean. Little backfire through intake. Then, I went rich. The sensor plate fluttered at times during this process. Now, in the past I typically stopped turning the screw CW when backfires out the exhaust occurred at idle, but I decided to keep going. I think I finally turned it about 1/4 of a turn all at one time. I revved the engine and, guess what? No backfires throughout the rev range and at steady low range rpm and no sensor plate flutter. I drove the car about ten miles, and it ran like a dream. Right now I am very happy. I've been fiddling with this car for a while. Maybe good driving days are yet to come. So, for now, I'm going to hold off sending my FD to gracious Tony. Let's see how it does in its current setting.

[allaircooled]

Good, sounds like you are sorting it out. Keep us updated on how it is running and if the oscillation stopped permanently.