donbryce

Does anyone know how the A/C causes the idle to increase when on?

If the air conditioning is on, shift in P or N, it idles fine, steady at about 700rpm. If it's in D, A/C on, like at a stop light, the idle surges 700 - 900 or so, up and down. If the A/C is off, it idles steady in any gear, around 700.

The shop manual says it should be 700rpm, A/C on or off. So, something is amiss when the air is on, sending the ECU I presume to raise the rpm's, then lower them, then raise....etc. I'm not looking at the IAC or IACV, since it idles perfectly when the air is off.

...or is this 'normal' engine behavior for this car? I've only had it about 1 1/2 months, and the A/C works fine.

capnfred

The idle speed is controlled by the ecu...a signal from the AC tells the computer to give it a bit more idle speed..... your IAC my need cleaning not too hard.... good luck..

capn

sbristow84

iTrader: (1)

I have this same problem. Found this on youtube. It is for a 1999 Camry but it still has the 1MZFE motor in it.

Gonna try it next paycheck

http://www.youtube.com/watch?v=i82s4ZfR2js

sbristow84

iTrader: (1)

I did it and it works a little better now. Still kinda surges when I first turn it on. But after that it works fine.

brandoe91

iTrader: (1)

He has the 3vz-fe though but should be similar .

donbryce

I just got my 2 volume service manuals, and it looks like the IAC valve is on the side of the throttle body (3Vz-FE engine). It may be accessable through that 'port/opening' though, just not in the same place. However, if the IAC is dirty, why would the idle be perfect unless the A/C is on? I'd think it would be rough under all conditions. Anyway, when time permits, it shouldn't hurt to try cleaning either on the car as in the video, or at the bench, as long as I don't disassemble the valve itself.

donbryce

I tried spraying throttle body cleaner into the intake, of course with the rubber hose off, and lots of cleaner around the IAC. After, the idle went way up and stayed there, about 1200. I guessed that I might have gummed things up worse, so I removed the bugger and thoroughly cleaned the plunger section.
I did the tests recommended in the shop manual, and got readings of 59/60 ohms across the plug pins B1 - S1/S3 and B2 - S2/S4. The book says it should be 10 - 30 ohms. When I did the check to make the motor pull/push the plunger, it worked fine.
Now, back on the car, after several starts/stops, the idling seemed to settle in at 500 - 700. I was happy until the car got warmed up, then the idle returned to 1000 or so.
It doesn't 'hunt' anymore, the reason for my original post, A/C on or off....but I'll need time to see if it goes down to 700 and stays there, warm or cold.
Anyone care to explain why the measured resistance of 60 ohms is so high? Were there several versions of this valve?
Here's a good pictorial of the units insides. I left the 'motor' part alone. http://www.toyotanation.com/forum/sh...ad.php?t=86540

donbryce

Well, one ****** up after another. I had the multitester on the wrong scale, so the re-test indicates the resistance is not 60 but 28 or so, well within spec. I removed and inspected the unit again, found nothing wrong, put the rotator in a slightly higher position on re-assembly (a 1/4 ccw turn). On the car, it idled great until it warmed up, now consistently 1000 - 1200 and stays there in 'P' or 'N'.
I'm starting to think that it may have idled right when it was dirty/partly clogged, but the valve was open too far, thus aproximately the right flow of air. Cleaned, still open too far, or some other air leak, it now gets too much air and idles high.
I'll look at other things now that could cause the valve too be opened too much, or other sources of air like a leak or throttle plate not closed fully.
Anyone care to comment on this diagnosis? It's very frustrating that it did idle fine with the air off before I STUPIDLY shot a bunch of cleaner into the intake.
After a lot of searching, I found many complaints of high idle after TB cleaning, and quite a few were solved by adjusting or replacing the TPS. That will be tomorrow's job.

donbryce

(This is a RARE follow-up post, here anyway, on the outcome of this job. Thanks to all who contributed).
I bought a 'refurbished' IAC off EBay, about $80.00 delivered, just in case I had messed mine up. While waiting for it to arrive, I pulled the throttle body and gave it a thorough cleaning , careful to avoid spraying into the throttle position sensor.
As it was easy to do on the bench, I tested the TPS per the manual instruction, and the 2 ohm readings across the IDL contact were off. That seemed to indicate that I may have changed something during the initial cleaning, or the original 'hunting' at idle (reason for starting this thread) was related to this. I'll never know.
To reset the TPS, I followed the manual instruction, after scribing a sharp line across the housing/plastic case of the TPS, so I'd know where it was originally. The adjustment to ohms spec. had it rotated about .5mm counterclockwise. I seem to recall that this is the direction to lower idle speed.
After putting the throttle body back on, the idle speed was better, but still higher than it should've been, around 1000 - 1100 in park, 800 - 900 in gear (A/C on or off, and a slight increase with A/c on).
As luck would have it, the postman arrived shortly after with my EBay IAC, which I promptly installed. That brought it down more, and after driving around for a few trips, it's now nearly perfect, around 750, slightly lower in park or N.
Lessons learned here:
1. Take the time to remove and clean the TB and IAC ON THE BENCH, NOT SPRAYING INTO IT AND SCRUBBING ON THE CAR! All my woes started right after doing this. The TB can be removed in 1/2 hour or less.
2. Don't disassemble the IAC for cleaning, just remove from TB and spray/air blow the valve section on the bench. If the gasket is bad, make your own from stock sheet or buy one.
3. Follow the manual test procedures for both TPS and IAC before coming to any conclusions on what the problem is. They aren't hard to follow.
BTW, none of the posts on TPS testing mention using vacuum to pull off the throttle opener during testing. And, the 4 contacts are accessible with the TPS on the car. I used a couple of small spade lug clips with wires attached.

peshwa

Thanks a lot for these tips. I am in the same boat. I kept thinking that the newer throttle body gasket I put in has created a vacuum leak and is not sealing right. Like a mad man I went on tightening the bolts till one of them sheared badly. Luckily I had coated the sheared off bolt with anti-seize so it can be extracted easily.
I think I too may have actually unsettled the TPS in the process and I am having an erratic problem right now.
I just feel so stupid and idiotic right now. I am playing with my IACv to adjust the idle and it seems to have helped some. Hope I am not required to buy anything new....already put in a grand in this car :-(