idle up and down when warm

[hornett22]

any ideas? looked for vacuum and intake leaks.only found one around the throttle shaft at base of carb.i changed that and it didn't help.thanks,steve

[ARCHINSTL]

Steve -
Check out some of my posts about RPM cycling between 1900 and 2300 (but only when warm). While different from your idle cycling, the cause may be the same. This persisted before and after all vac lines and the carb were replaced, plus the HIC, PCV, and TVSV gizzies.
I was able to make this cyling cease by unplugging the vac line to switch "A". However, a downside is that the revs stay a bit up between shifts, leading to a higher fuel consumption than normal.
It obviously has something to do with the temperature rise in the coolant, but that is tied into so many other switches/valves/gizmos that I am at a loss.
Every switch seems to check out, per the wonderful FSM. I am almost at an opinion that the ECU, while primitive, may be at fault.
I have written the Mothership in CA and am waiting for an reply. If an answer is received, I will certainly post it.
It does seem odd that apparently no one else has experienced this phenomenon.
Tom M.

[Mickey_D]

Oh, mine does it as well.

But as the British say, I just can't be arsed to fix it!!

My particular Terc just isn't worth spending ANY money on.......

[hornett22]

no good.i will get it in again and take another look at it.i have some ideas.it's only since rebuilding the carb.i wondering if i got the two middle screws that hold the throttle plate housing on the bottom of the carb backwards.one has a hole through it,the other does not.seems like i have a intake leak at the throttle shaft still.weird.

[xirdneh]

no good.i will get it in again and take another look at it.i have some ideas.it's only since rebuilding the carb.i wondering if i got the two middle screws that hold the throttle plate housing on the bottom of the carb backwards.one has a hole through it,the other does not.seems like i have a intake leak at the throttle shaft still.weird.

i'm assuming you are spraying carb cleaner or something around the base of the carb to determime where the leaks are. its normal for the car to rev up a bit when you spray the throttle shaft at the base of the carb. the shaft does not have a seal so some air will be sucted in.
as the guy before me recommended i would try dissconnecting the "a" vacuum switch first. if that does nothing i would try the "b" switch. if that does not work try checking the accelerator cable. it may be to tight.
next double check the vacuum hoses. maybee a hose is connected to the wrong spot

then i would look at a possible mistake in rhe carb rebuild

[Paul]

My Terc seems to do this when it's warming up, but stops when it reaches normal operating temp. I did some poking around and found it related to the clicking of the VSV valve. When temporarily disconnected, the cycling stopped. This thing is part of the fuel evaporative emission control (EVAP) system, which receives some input from vacuum switch A and one of the coolant temp switches. Check page EC-9 in the manual. In my case, I think the charcoal canister needs replaced.

[ARCHINSTL]

Paul -
You know, I thought at first that the VSV was the culprit, because of the tie-in to "A", the coolant temp switch, and the canister (Evap system) - rather than the function of "A" in the deceleration fuel cut-off relationship, which I detailed in the previous post. Especially because the FSM states the VSV is negated when the decel cut-off function is on (bottom of EC-9).
I cleaned/tested all of the above in the Evap system per the FSM with no results - all supposedly OK. This testing was before the new carb/solenoids, though. However, I did not think to unplug anything until I hooked up with "A" by itself.
I think I will try leaving "A" unplugged, as it stops the higher RPM cycling when warm and first try unhooking the canister and then the VSV to see if it halts the "running on" between shifts.
When it stops raining, though - no garage.
Thanks,
Tom M.

[hornett22]

checked everything you mentioned.no good.disconnecting vacuum switch does nothing.i'll pull the carb back off.i was using propane for the leaks.i did try carb cleaner as well.