Idle surging/revving

[Elvis]

How funny - I've been telling this for many years but nobody gave a sh..

I asked people to help to search for the root cause but all I got was to be blamed not to help :-(


My guess is that the bearing is worn and the reacts on the vacuum on the throttle plates
or
the spring has lost force.

solution is to bend the spring at the throttle plates a bit and give it a bit more kick.
That worked for my car and two others I had here.

All the other here will tell you something different - therefore - this is my solution,
it works perfectly for >10 years now, I never had to use the new butterfly unit I
bought in Houston back then.

Well the problem is back but I’ve found (hopefully?) the answer:
the throttle is sticking and not activating the idle micro switch.

I had tested this several times with the engine not running and it always check out fine. I could hear the click from the switch every time I let my foot off the gas pedal. Well today it acted up (2,500 RPM in park, no lower than about 1,700 in Drive) and I pulled over, popped the engine cover, and pressed on the idle micro switch. Immediately the idle dropped way down. Took my finger off, idle surged back up.

So, I’m going to try just lubing the cable, spool, spring, etc before I make any adjustments. Any recommendations for lube?

[CFI]

solution is to bend the spring at the throttle plates a bit and give it a bit more kick.
That worked for my car and two others I had here.

The springs are all greased up. I’ll bend the throttle plate spring next. Thanks.

[David T]

The throttle system has 3 springs. Two are in the throttle spool and one is on the throttle body. (There are also 2 springs, one each on each decel valve but that has noting to do with getting the throttle arm all the way back to idle). Even if you tighten up the throttle spool springs, and/or the throttle body spring, it is not always enough to get the throttle arm to trip the idle micro if you have a lot of play (looseness) in the quadrant link ends. My quick fix is to lengthen the quadrant link but it does mean more lost motion in the throttle pedal. Remember the quadrant link has a left-hand AND a right-hand thread for precise adjustment and it also has the little clips like the door struts to prevent the ends from popping off.

[CFI]

My quick fix is to lengthen the quadrant link but it does mean more lost motion in the throttle pedal. Remember the quadrant link has a left-hand AND a right-hand thread for precise adjustment and it also has the little clips like the door struts to prevent the ends from popping off.

Wouldn’t you want to shorten the quadrant link? Seems like lengthening it would push the bottom of that rocker arm and create a wider gap between the idle micro switch and the adjustment screw that trips it.

Between greasing everything up and making slight adjustment on the idle micro switch adjustment screw everything seems to be working normally. Thanks everyone for the advice.