91RN81

Hey guys got a issue with my 91 toyota truck 22re. When i turn on the a/c it will occasionally at a stoplight start surging idle wise. It seems to surge at least 300-400 rpm and then stop after about 20-30 seconds. Only happens when the a/c is on. You can definetly feel it inside the cab but not too bad. A/C blows ice cold though. What could be the problem and how can i fix it? thanks!

seaflea

the AC idle up valve needs to be adjusted. check out
www.4crawler.com for the causes and corrections. or you can PM him.I woulld try yo explain right not now but I'm not sre how long I will have power.......

91RN81

I dont see any information about this on 4crawler.com??

seaflea

Sorry about that. I had sporatic power yesterday.
The AC idle up valve is located on the intake plenum (around the middle)
and can be adjusted.
The problem, it seems is that youre idle with the ac on is at or around 1200 rpm. That is the magic # to turn the AC compressor on. if it falls below that it will kick off. And the reverse will turn it on, causing it to surge. The answer to this is to turn the Idle valve up some and keep it from going below 1200 RPM.

PS I'm not sure which way to turn it to make it change.

Good luck and let me know how it turns out.Feel free to PM me if needed.

4Crawler

iTrader: (3)

You have the A/C fast idle set too high and this is causing you to hit the ECU's fuel cut RPM when you apply the brakes, see this recent Toyota Trails Truck Tech column Q&A:

http://www.4crawler.com/4x4/TLCA_Tru...ech.04.09.html

Note: I can exactly duplicate this on my '85 if I crank up the A/C fast idle setting too high. If I turn the fast idle down the problem goes away.

seaflea

Thanks Roger

JamesD

Clean your throttle body. Then try it. Clean the living crap out of it.

James

Gatz101

I have a similar issue. I can only get an increase in RPMs during a cold start. For example, when I crank the truck after it has been sitting for hours the RPMs reach 1200 or so and levels out after 10 mins to approximately 750. If during that cold start I turn on the AC the RPMs go to approximately 1400. I also hear the compressor and maybe a relay kick in. While the RPMs are leveling off with the AC on the RPMs drop to 500, sometimes lower to the point where the engine sounds like it might stall or turn off but recovers. (erratic idling) The engine runs erratic for the first part of the drive and recovers when I reach a certain speed or RPM. If during the cold start I leave the AC off (and during the drive) the RPMs stay at 750 when idling. Now, I have gotten to the point where I choose to leave the AC off knowing that the engine will run smoother and accelerate better. I have seen older posts on the internet that mention older cars and the need to increase the idle speed in order to run smoother with the AC on. All I know is that in the two years I have owned it I have been able to change the idle with the idle screw but now the idle screw does almost nothing (with the ac off of course) to the RPMs at idle. When it does the ECU seems to correct for the adjustment after driving it several miles. I have adjusted the knob in back of the glove box and then had to adjust it back since S.Texas is so hot and my kids were baking at red lights. Any ideas? Do I need to fiddle with the ac idle valve, knob behind the glove box, and idle screw in unison? Help would be much appreciated.
By the way, I have cleaned my throttle body but never removed it. It looks clean. I did notice carbon build up at the bottom of the idle adjustment screw when I was inspecting it a couple months ago. I cleaned it off but still no change. The idle screw had an O ring that I hadn't seen in any of the literature. It was flush with the screw's body and was sort of a hard plastic. I removed the plastic and added the correct size O ring and still no change in the idle.

4Crawler

iTrader: (3)

Yes, set the A/C idle-up valve to just bump up the idle a bit over normal with the A/C on, to keep the engine from bogging down and to keep the A/C blowing reasonably cold at idle.
Then the adjustment on the A/C amplifier box under the dash should be set at just a bit below normal idle RPM. That's there to cut the A/C off if the engine is bogging down with the A/C on.

briholt

I'm aware of the plastic star knob in the engine compartment but there is another knob under the dash?

4Crawler

iTrader: (3)

Yes, that's for the A/C amplifier.
Where it is:
https://www.4crawler.com/4x4/CheapTr...ne_Pix/20.html
Description of how it works:
https://www.4crawler.com/4x4/CheapTr...html#Alternate

briholt

Thanks crawler...I read that post but I guess I'm just not seeing an obvious "knob"...I'm seeing how you jumped that low pressure switch..and a little black nipple thing near by, below and to the right ..is that it?

4Crawler

iTrader: (3)

I don't think it's quite visible in the photo but it's just above those connectors. I recall it's a small black box with a light colored knob w/ screw slot and an arrow showing which direction increases the setting.

briholt

Well, I don't think I'll need it because dropping the idle was enough.

I was about to tear into the idle air control valve after checking the brake booster but I think this was it. I've got a 91 and I don't drive it much but I seem to recall chasing the solution each season...that when it gets cold I'll have the surge again.

THank you much for this thread, these recent answers, and 4crawlers history of help.