J. Stovall wrote:
>
> Hey all,
> I got the battery back today and dropped it in. I then tried my
> timing light again, and it worked! After, I played with the carbs and got
> it real tuned up. Now, it's just-amazing.
> Okay, you knew it was coming: I have a question! When I start the
> car, it idles at about 1200. This is good. When I rev it, it likes to idle
> at some high point it chooses itslef. I know it probably has to do with the
> carbs, but what do I do to stop it?
> SNIP
> Good luck and thanks!
>
> Jeff Stovall
> jstovall@earthlink.net
> "I'm God's gift to humility."
> 1966 Triumph GT6 mk1
Jeff
I had a similar problem with a ZS 175 CD carb in my Stag. My symptoms
were as follows;
1) When I started the car it would idle nicely at 800 RPM.
2) After a minute or so it would suddenly jump up to roughly 2000 RPM and
the left side carb would be flowing a lot more air and fuel.
3) If I revved the car up when it was a slow idle it would stay at the
faster idle setting.
4) At high idle, if I momentarily placed my hand over the left side air
intake and choked off the flow through the offending carb the idle would
temporarily return to 800 RPM after I removed my hand.
5) The problem would persist even if I adjusted the idle screw so that
the throttle plate was completely closed.
6) The problem didn't go away or even get a bit better when I did the
required voodoo dance.
I had just rebuilt the carbs and everything was new. I spoke to a number
of supposed carb experts (this was before I was on the list) who gave me
a large number of dumb answers. I finally got the right answer from a
fellow named Joe Curto in College Point NY, 718-762-7878.
For me the problem was a bypass diaphragm on the side of the carb which
allows air to bypass the throttle plate and enter the engine when the
throttle is closed quickly. In my case the diaphragm was initially
closed when I first started the engine but for some reason would
eventually open up allowing substantially more fuel and air into the
engine (around the closed throttle plate) and thus the fast idle.
Previous to my conversation with Joe I had suspected the bypass unit and
had replaced the internal diaphragm (note this did not come in my rebuild
kit, I had to order it separately) and even switched the entire bypass
unit from the right side carb to the left side with the problem staying
on the left side. Joe told me to take off the left side bypass unit and
place duct tape over the two holes. Sure enough this solved the problem.
At this point instead of trying to figure out what was the root of the
problem, Joe suggested that I adjust the internal screw in the bypass
unit so that the diaphragm was permanently held closed (he said that it
was just a minor emmissions device and was not needed for normal
operation). I did this and have not had any problems with high idle
since.
I don'y know if your carb has a similar device. If it does I hope that
this information helps, if it doesn't..... never mind.
Good Luck
Dan Pruzan
71 Stag
Santa Clara, Ca
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