When A/C is on, idle wonky...

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HypocriticalHippie

HypocriticalHippie

10 Year
Joined
Jul 9, 2011
Threads
13
Messages
74
Location
Phoenix, AZ
When A/C is on, idle wonky... !!!FIXED!!!

For lack of better terms, when the A/C is on in my '94, the idle will start to die over the course of about 7-10 seconds. Sometimes it pops back up to normal, other times it dies. When it does pop back to normal, it will do the same thing again within 20-30 seconds.

I have recently changed the O2 sensors and wiped the ECU. The truck has since had about 20 starts and 60-70 miles.

The only thing that I know it might be is the throttle is stiff and I haven't isolated if it is the throttle cable or kickdown.

Am I looking at ICV?

I have read threads till I'm blue and have not seen the resolution of this problem.

Thanks,

Scott



PROBLEM FIXED!

Cliff notes: Bosh Universal O2 sensors #15731 gave my truck a very bad surging idle. Ordered NTK#24044 for $57 through Amazon and the truck now runs perfect.
 
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Is it too low idle RPM ?

If it's solve while you holding gas pedal little bit then you can adjust throttle cable to keep slightly higher RPM.

I use scan gauge to see RPM and adjusted it for around 620 RPM stays.
 
A/C off, it idles at 635 RPM. Pretty close to perfect.

A/C on, idles higher 750 or so. It will be idling perfect, then start to shake as it's missing, it tries to catch itself (idlles back up), miss more, catches itself...

Each time it misses, it idles lower until it may or may not die. If it doesn't die, it springs back up to a perfect idle.

Scott
 
When the AC compressor kicks on the IAC is supposed to increase the throttle to around 800 or so. This will cycle with the actuation of the AC compressor. If the truck idles normally at 650 and kicks up to 800 with the AC on, this appears to be normal to me.
I'm not following your description of when the idle drops.
 
Yes, but it hunts in between idling normally. For example, it will idle normally for 15 seconds at the light, then start to hunt, it will then either die or not. If not, it idles normally, until it does it again.
 
Had a car that would do this when it was low on freon. It would idle up when the AC kicked on, then the compressor safety switch would shut off the compressor and it would idle back down, then it would kick on again and nearly die
 
Okay, I cleaned my throttle body and replaced a few vacuum lines. None were leaking that I know of. Reset the ECU.

When I started the car, the idle briefly went to 1400 and dropped down to normal cold idle. Perfect. I adjusted my tranny cable as well.

When the A/C is switched on, the car still has the same problem. Normal idle is rock steady, and is as well when the A/C is on, except for avery 30 seconds or so, it wants to die.

It does not idle like it has any vacuum leaks. Any ideas?

Scott C.
 
The only thing that I can add about the A/C is that it is cold and will freeze you out of the cabin, even in Phoenix. I do not know where the charge is at, but I am assuming that it is close to correct.

Retrofive, are you into BMWs?

Scott C.
 
Update...

Update, in case anyone searches this and needs info.

*Cleaned throttle body.
*Cleaned ICV.
*Replace PCV and hose.
*Replaced valve cover vent hose (was cracked).
*Adjusted tranny cable.
*Replaced all of top side vacuum hose except beneath EGR. No under manifold hoses were touched.
*Intake tube seems somewhat pliable and does NOT look to be cracked or even checked.
*O2 sensors were replace with Bosch #15731. Before I get grief for this, the truck runs absolutely fine in all other instances. But, it did start after clearing codes when replacing them.
*Aftermarket alarm had to be disabled after it armed and killed the ignition when battery was reconnected after O2 sensor swap. This involved removing alarm wiring from ignition.

Did not clear ECU after last round (ICV and vacuum hoses). Truck still idles fine then surges with A/C on. If it doesn't die, it springs back to life and idles fine, to surge again in 10-30 seconds. *when watching this under the hood, I never noticed the compressor clutch cycling.*

If A/C is turned off when car is idling, it may still surge and die, although the surge stays longer in troughs.

If truck is started without A/C on, it does not surge or die at all. Idles rock steady around 600.

Could there be an incorrect charge in my A/C compressor that is causing this?

I am open to most suggestions. ;)

Scott C.
 
Belts? It was suggested above....
 
Well, lesson learned...

After doing all of the aforementioned fixes, I went back to the one thing that I changed that started this mess. Yes, the oxygen sensors. I replaced the O2 sensors with Bosch Universal #15731. The truck ran great, except for the above problem.

Tonight, at close to wit's end I crawled underneath and unplugged them. The truck ran like it was brand new with zero surging. I called my wife to come out and have her take it for a spin, since it's here DD. When she came back she said, "I hate to tell you this, but it felt really peppy." Problem solved.

Now, where is the best deal on stockers, unless someone can recommend a different number or brand to try?


Cliff notes: Bosh Universal O2 sensors #15731 gave my truck a very bad surging idle. Always use the KISS (Keep It Simple Stupid) principal when working on your rig. If you mucked around with something and your truck isn't running well after. Go back to square one before messing around with other solutions to your problem.
 
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For OEM O2 sensors, I recommend calling CDan or Beno at American Toyota (number can be found in the vendors section or by searching) or you can also look in the vendors section as there are a handful of OEM parts providers.

Good luck and glad to hear you have things figured out.
 
The solution to this problem was new O2 sensors. Apparently, my truck didn't like the Bosch universals. I ordered some NTK#24044 through Amazon for $57/per and the truck now runs as if brand new. A little curiosity that I noted was that one of the original O2 sensors that I pulled off was labeled as NTK and Toyota, so they may provide OEM?

Scott
 
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Very good to know. I also have a 94 and have been wondering if any non oem O2 sensors would work. I might just get a set to keep on hand... I can afford to keep spares that work at that price. Thanks for following up on the post.
ETA also curious about the ntk and Toyota labeling ... I know a lot of my factory parts are cobranded Denso, I thought maybe the Denso O2 sensors would work.
 
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