idle rate is being a whore

[Chubs87Accord]

ok when my car is sitting there and running sometimes my idle rate start goin up to where the needles hittin 2.. but ill tap the gas to rev it and it goes down to a normal rate.. anyone know what this may be.. and please god dont let it cost a lot :bow: :help:

[A20A1]

you may have a vacuum leak.

[A20A1]

Or it has something to do with vacuum.

Anywho if vacuum is leaking then the idler will put more pressure on the throttle. The idle diaphragm needs vacuum to control throttle, with low or no vacuum the spring presses the idle diaphragm out and the throttle opens increasing the engine rpm.
When vacuum is high the diaphragm pulls inwards, the throttle closes under the tension of the throttle return spring, and engine rpm drops.

What i think is going on is:
after a period of time when the car is sitting still the vacuum drops somewhere in the idle circuit, so the idle diaphragm compensates by opening the throttle.
Since the vacuum leak is small, basic engine rpm doesn't drop, but the idle diaphragm is losing vacuum so you get a rpm surge.
When you press the gas vacuum drops to 0 or gets very low... when you let go of the gas the throttle snaps closed creating a sudden restriction which casues high vacuum and the idle diaphragm goes back to normal.

[A20A1]

I suggest testing the idle diaphragm with a vacuum pump to see if it hold vacuum. if the diaphragm is ok then test the vacuum lines... I'm not sure where the idle connect to since I don't have a stock carb set up to look at.


it also could be the choke

[1988starter]

When I replaced all my vacume tubes my car was much smoother.

[Chubs87Accord]

well.. honestly i have no idea how to test that stuff.. if it is how much would it cost to replace the tubes and stuff?

[A20A1]

buy a couple of feet of 5/32 rubber Vacuum line.
Sometimes they lable it as Windshield washer / Vacuum tubing

You'll need a hand vacuum pump to test the diaphragm... I don't know how much it is to replace the diaphragm, but the vacuum lines are cheap... 5.00 for 4' - 6' something like that.

[startersgirl]

For my 88 LXi it took almost 20 feet of 4 mm tubing.