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Discussion Starter #1
Whenever the engine is warm and the A/C is turned on, the idle fluctuates between around 675 and 950 RPM. Without the A/C on it idles great at about 750! Any ideas?
Also I'm going to do a smoke test soon to test for vacuum/intake leaks, but I've never done it before and don't know where to put the smoke into!
 

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1998 Rav4, manual transmission, 2WD, JDM engine installed in 2013
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Weird idle with the A/C switch on is a symptom of a bad A/C system circuit (like a short somewhere). See page 20 of the attached diagnostic service manual section. I am looking for the relevant wiring diagram and the A/C service manual section.

What bothers me a little is that you just cleaned the IAC valve and throttle body, to address the engine dying at idle, right? The coincidence of today's problem with the problem just a few days ago (presumed resolved via cleaning the IAC valve and throttle body) is a bit troubling.
 

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Discussion Starter #3
I do believe that it is a problem with the A/C and not the IACV because the problem I just described was present before I cleaned the valve :) and it only occurs when the A/C is on (I believe). And oddly enough, I'm having trouble finding the A/C service manual section as well
 

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I am looking at what I think is the equivalent A/C service manual section for a 1998 Camry, and the check is just a continuity check of the switch when on and off. I think maybe the more prudent troubleshooting approach is to look at the a/c control switch on the electrical diagram. See PDF pages 158-159 of the attachment. (I think the 1996 Rav4 is the same as the 1998 Rav4 for the a/c switch troubleshooting et cetera.) Notice how the A/C control switch sends (or receives?) signals to the computer.

In my experience, when there is an electrical problem, the first candidate for failure is a switch. In this case, the "switch" is pretty complicated. It has a few diodes and resistors inside it and I presume a circuit board. I would be inclined to go to my local salvage yard and buy a used replacement A/C switch and see if this fixes the problem.

Alternatively, I would be checking for grounds in the A/C switch wiring. Prior to checking for grounds, I would take some care to disconnect the wires at the engine computer in particular.

I am also checking this site and toyotanation.com for reports of replacing the switch in response to idle problems. So far I am not turning up much.

Of course, the problem could be other components in the A/C switch circuit.
 

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Does the idle speed change when the A/C is on correspond to when the compressor is running and when it is idle? With my vehicle the idle speed increases when the compressor is actually running - evidenced by colder air coming from vents when the compressor is running. But your idle speed fluctuation range is somewhat greater than might be expected.
 
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Discussion Starter #7
Interesting... I’ll poke around the engine bay and update if I find anything, but if not I’ll just assume it’s normal enough!
 

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I do not use my Rav's a/c much when driving around town. But today with the outside temperature where I am at about 80 degrees F; with the engine fully warmed up; and while running errands I ran some tests. When I came to a stoplight, I put the cabin fan on low and pressed the a/c button. The idle went from a steady 700 RPM up to around 1100 rpm and then declined in a few seconds to about 900 RPM. It held steady at about 900 RPM. After a few several minute stops (doing errands), I tried the a/c again at a stoplight. This time the idle RPM went from 700 RPM to about 900 RPM and held steady at 900 RPM.
 

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Discussion Starter #9
Interesting, I use mine a lot (florida weather), and the RPM cycles happen about every 15 seconds. It does sound like it corresponds to something in the engine bay engaging, so it’s probably just the compressor.

On a totally different note, the steering started being weird! Whenever going straight down a road, I have to hold the steering wheel about 15-20 degrees to the right
And when turning left, there seems to be a point in which the amount of steering input does less than it does normally if that makes any sense.
Whenever I get the chance I’m going to check things out under there, tighten up the steering rack, see what’s out of place. Any suggestions off the top of your head?
 

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-- I attach part of the HVAC service manual section for a 1999 Toyota Rav4. From this section, and like Blogson and Mick noted:
"[Checking the] IDLE AIR CONTROL (IAC) VALVE
Start engine and bring to normal operating temperature. Turn A/C switch on, set blower switch to high position and adjust temperature control lever to maximum cooling. Ensure compressor clutch is engaged. Using tachometer, ensure when compressor clutch engages, idle RPM increases 100-200 RPM and decreases a similar amount when clutch is disengaged. If idle does not react as specified, check IAC valve and air intake system."

-- Regarding the steering problems, are you hearing noise, as in air in the power steering system? Here are the checks I would do: Check the air pressure in the tires. Check the tires for uneven wear. Check the power steering fluid level in the reservoir. Check for signs of the (well-known) leak described in this thread DIY: Replace Power Steering Rack Seal (Pinion Valve... . I would drain the PS fluid; flush the system a bit; and replace the PS fluid. I would have an alignment done.
 

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Discussion Starter #13 (Edited)
Update on the steering issue: the rubber piece (bushing) that goes between the bracket and the steering rack has moved out of place so I’m gonna try to get it back with minimal disassembly
This bushing is right behind the boot on the steering rack

*Update to the update - you can do it without removing anything except the passenger side wheel!

Undo the bolt on top of the bracket and bend the bracket a bit outwards,

push the brake caliper towards your left (facing the passenger side of the car) to get the rack to move upwards a bit,

shove the bushing in, use pliers to bend the bracket back, and tighten that bolt back up!
 
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