AC idle boost solenoid valve location not found - 86LXi

[AC439]

Hi there, long time no post. Hope everybody doing fine.

I just found out my 86LXi (AT) will no longer boost engine rpm when AC is on during idle. I read the FSM to page 12-40 and the picture show about the valve. But when I went to look for it, its not found. Instead there is a little black rectangular box to the side of the air filter housing that connects between the AC idle boost valve and the Idle control solenoid valve. This black box doesn't have any electrical wired connects to it. As you can see from the pics, there is nothing to the right of the idle control solenoid valve (page 12-40 shows the AC idle boost solenoid to the right of this valve). Then there is this mystery box bolted to the side of the air filter box sits between the AC idle boost valve and the Idle control solenoid valve. On page 12-42 left side middle diagram, it does show the mystery box to the side of the air filter housing and in the same diagram, it does not show the AC idle boost solenoid. Am I missing something or the FSM is inconsistent ? Thanks.

[Dr_Snooz]

Not sure about the '86s, but the LX-i's don't have an AC boost solenoid. It was integrated into the IACV.

Yeah... good luck with that.

[AC439]

Not sure about the '86s, but the LX-i's don't have an AC boost solenoid. It was integrated into the IACV.

Yeah... good luck with that.

Thanks, I will look more into IACV.

[AC439]

I'm resurrecting my thread. After get the paint done, I'm back to mechanical. Still having this issue with A/C idle intermittently not boosting (actually 90% of time not boosting).

Today I took apart the vacuum box, got down to the two solenoids inside. I yanked them out and tested them both with a 12V power supply. The A/C idle boost one seems to give me click sound when I applied 12v. Hose #19 connects to the A/C idle boost valve (on intake plenum) holding vacuum without leak. The other solenoid is dead (Ignition Control solenold valve) - this is the one applies vacuum to the outer port of vacuum advance to give an additional 4 degree advance when car is cold, no big deal on this one). I checked the check valve between there as well and its fine.

I then took out the A/C idle boost valve from the intake plenum and cleaned it well with throttle body cleaner spray. Put everything back and volva ! I have A/C idle boost back ! Adjusted the screw on the valve to get the right amount of boost. I was happy.......then later this evening went out for shopping, it worked at first and then I got no idle boost on my way home !

I'm thinking its mostly likely the solenoid. Its a moving part and 31 years old. If it happens again, I'm going to vacuum test the A/C boost valve to make sure it gives a boost. If this is the case, I will probably need to replace the solenoid. I don't think there is any more parts available or even junk yards don't have our cars anymore. I have to buy after market, mount them separately and rewired everything.