Fluctuating Idle - Carbed '87 Accord

[Lester Lugnut]

Found one thread with a similar title as mine, but it pertained to a fuel injected Accord. Mine is carburetted.

Once the vehicle is fully warmed up and idling in P or D, the rpms will fluctuate up and down.

Have looked all over for loose/cut/disconnected vacuum hoses - none found.

I realize there are about a million vacuum valves on this beast.

Anyone have an idea where to go from here?

Thanks.

[SiR]

Might be anyone of the (3?) idle control diaphram. The lines going to them might be alright, the diaphram, in a lot of cases, are leaking. In your case, you got the tranny, A/C, and might be some main idle diaphram. Hopefully someone else with pics and more indepth about carbs are here to help you.

[A20A1]

A drop in vacuum to the diaphragm itself will cause the idle to raise, then when vacuum is returned to the diaphragm it pulls away and the idle drops. Something is causing the diaphragm to recieve a fluctuation vacuum signal. Worn or broken Gaskets, vacuum lines, diaphragm, and valves / solenoids can cause vacuum problems.

Bad sensors can cause solenoids and valves to behave differently.
Low coolant level can cause thermovalves to respond slower or not work right at all. But I doubt this is your problem since your idle is still good after your car warms up, it's just unstable.

Have you checked for leaks with the carb cleaner method?
Besides a leak, Ignition problems can cause loss of vacuum.

You might want to remove your PCV valve and see if it rattles. Replace it if it doesn't rattle.

You can check your fuel system along with electrical and also the float level if you run out of ideas.

[Lester Lugnut]

Made a discovery tonight while working this issue. Refer to the URL at the bottom of this post.

Item 41 in the photo is the TA sensor assembly. I think the TA refers to temperature. Not far from item 41 is item 22 and 23. Both are listed as air intake sensors.

When I removed the white electrical connector that was attached to item 41, the fluctuating idle disappeared.

It's late and I'll pursue some more tomorrow night. I also want to experiment with plugging the vacuum lines that attach to item 22 and item 23.

Don't want to rush out and buy these as they are all approx. $50.00 each.

Will update this post when I know more.

http://www.slhondaparts.com/browse.a...ViewParts=true

[Lester Lugnut]

Reviewed Ch. 11 of the '87 Accord factory service manual.

The ECU or control section starting on page 11-80 listed the following as being the most likely to be involved in a fast idle/surging scenario:

- Frequency Solenoid Valve C
- Idle Boost Slenoid Valve
- A/C Idle Boost Solenoid Valve
- Frequency Solenoid Valve A
- Frequent Solenoid Valve B

Checking these requires a vacuum gauge and voltage-ohm meter. Access to the ECU under the drivers seat is also required in some cases in order to test voltage at specific pins.

Before tackling this, I decided to give the carb-adjustment section of Ch. 11 one more pass.

I ended up readjusting the adj. screws on both the left and right side of carb, the black throttle stop screw in the back and the a/c idle boost screw adjustment screw on rear of carb.

High idle and wild surging are now gone.

[Lester Lugnut]

Back to the drawing board. Ran great for 3 days - the best it's run in a long time.

Last night the idle started jumping up and down and the car would die when brought to a stop.

Someday.