I just got my truck back from the shop with a new motor and everything is pretty good except when I turn on the a/c, the idle will start to surge. When the a/c is off, it idles fine. I had this problem before, and I think I fixed it by turning the idle screw in some. I also noticed a little white knob on top of the intake that looks like it may be related to the idle. Any ideas?

 

that's the a/c idle up valve, it's purpose is to raise the idle speed when the a/c is turned on.
now, by 'surge' what do you mean? it just revs up to a higher rpm, or fluctuates up and down?

 

The adjuster on the intake with the big spring under it is the AC idle up. Turn it in a bit so the idle is not so high with the ac on.

 

it revs up then it's like someone turned the key off then back on again just before it dies. it does about one cycle a second.



with the surge up and down which way should i go with it?

 

Well don't know if you have the 3.0 (I do on my 93 pickup) and had a similar problem with my idle and AC once I got it back from the shop (had a new compressor installed.....to damn hot here in Texas). Anyways I was searching and reading up as much as possible on the forum for the least expensive troubleshoots. I solved my problem by replacing the PCV valve (about $4 at your local Toyota dealership) and adjusting the idle screw to get the idle back down to 800 RPM (was at 1100 RPM....don't know how it got there). Prior to doing this my truck would surge from 1100 RPM to 1500 RPM and then would stay at 1500 RPM and surge again from 1500 to 1750 RPMs with or without the AC on and every time I was coming to a stop or at a red light. After adjusting the idle and replacing the PCV valve no more problems.....I just drove it 500 miles back to South Texas and it works great.


But there's my .02 worth and relatively cheap and easy. Give it a try if you haven't done so yet.

John

 

are you sure that your ac system is fully charged? if its low it would cause your compressor to kick on and off frequently.. which might do something like you described?

 

is the AC blowing cold still?

sounds like maybe just the idle-up valve is out of adjustment like mentioned...

with the truck running and the AC on (assuming the compressor's kicking on and blowing cold air), face the motor from the from of the truck. Looking at the intake, on the right side about right in the middle is the idle-up valve; has one large hose connected to it from the throttle body, and 2-3 little hoses (depending if you have PS) coming off it going over the valve cover.

Two of the little hoses go to the solenoid furthest to the front mounted on the valve cover, and if you have a 3rd one, it goes over to the PS pump.

On top of the valve pointing up should be what looks like a white plastic screw; six sided with a slot for a philips head screwdriver.

Turn it clockwise; in other words tighten it down a little at a time. The idle should steady and level out; I've set mine about 200 RPMs above normal idle with the AC off.

Of coarse, all this is assuming you have the 22re... I have no idea if you have the 3.0

 

Yes, just turn down the fast idle speed with the A/C idle up valve.

 

If your idle is to high when the throttle plate is closed (idle) the computer will force a bouncing idle that you describe. Get your idle down and it will go away. You must have an idle under 1000rpm or you will have this condition.

 

Yes, I have the 22RE. As soon as it's light in the morning I'm going to go out and try this.

 

So maybe the a/c idle valve is forcing it above 1000rpm which then causes this only when the a/c is on. I'm gonna try iamsuperbleeder's suggestion in the morning.

 

Well, now it won't do it. Guess next time I go somewhere, I'll have to pull over somewhere and try it.

 

the search is a wonderful thing

I found this thread and this https://www.yotatech.com/forums/f16/...-idle-c-67437/