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Need IAC valve advice

2K views 12 replies 4 participants last post by  cknight363 
#1 ·
Hello all,

Our newly acquired 98 Camry showed it's first flaw this week. It's been warm so we used the AC. We drive several miles on the highway and one of the highway traffic lights changed so we had to come to an abrupt stop. The idle started fluctuating and i thought it was going to stall. When I hit the gas it bucked one time then was fine. Then it did it once again. Reading on here it appears to be a problem with the IAC valve. I have found easy and complicated cleaning procedures, but want to try the easy first which involves removing the center hose from the bottom and removing the electrical part so you can manually turn the valve left and right while you put throttle cleaner in the opening inside the throttle while plugging the hose outlet. I also plan on cleaning the throttle plate. I am pretty sure it's never been done @ 58K miles. I am trying to get access and have run in to a couple of "issues" first, the box thing that hangs on the bottom of the air intake hose, appears to be hanging by a rubber tab attached to the hose with a pin with a mushroom head that pushes through. I can't get that out and afraid of breaking it. Second, the electrical connector on the IAC valve. I can't see or feel a lock on it and cannot get it to pull off so stopped. Any trick to getting these off?
I see that many with IAC problems have cold start issues but this starts on a dime every time. Only issue is with AC on and stopping. It is the 4cyl

Thanks for any advice!

John
 
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#2 ·
I would also check the ECT sensor because that can cause rough running once warmed up as well IIRC.

To test the IAC valve:

- let the car warm up (to where it starts fluctuating the idle)
- pull the air intake hose off the throttle body
- cover the IAC port with your finger
- if the idle smooths out, it's the IAC

Personally, I like disassembling the IAC after removing it from the TB, then retrofitting Allen screws and split-lock washers to make it easy to take off in the future. For the first time, remember that the screws are JIS, not Philips, so you will want a set of JIS drivers. To do this, you need to remove the TB...pull off all the hoses and undo the four 12mm bolts that hold the throttle body to the intake manifold (IIRC two are shorter, so don't mix them up).

That box you're talking about sounds like the resonator, I think with some wiggling you can pull out the whole air intake piping (top of airbox, hose, and resonator) as one piece. I can't picture your mushroom-headed pin, maybe you can post a picture?
 
#3 ·
Åw hell..Never heard of JIS screws and indeed stripped one screw, so sensor did not come off. Also odd, In every video I have looked at, there should be three hoses coming out of the bottom. Two cooling lines and one that leads from the IAC to the crankcase. This car only has two, both cooling. Also every one i've seen, the electric part of the IAC the screws are out in the wide open. Mine are recessed.
What I ended up doing was running the engine and spraying throttle cleaner in the opening. I turned on the AC and when the AC would engage, I would hear more of a sucking sound coming from the throttle opening and the idle would increase slightly. The throttle plate was pretty dirty so gave it a good cleaning too. I think the temp sensor is working okay. I put one of those Ultra gauges on and it seems to be reporting coolant temp properly..Also the MPG is more accurate than our 2016 Impala!
So once everything was clean, It seemed to idle a bit low so I turned down the idle screw a bit. Took it for a big drive with the AC on, and so far so good. What is the purpose of the vacuum pot that appears to raise the throttle at the absence of vacuum? Is that to have higher idle at start? I thought perhaps it was to "kick" the throttle if the car was about to stall but that doesn't seem to be the case. I noticed if I pull the vacuum hose, it kicks the vacuum up a bit.
PS, the car idled as smooth as slik beforehand..This would only show itself on the highway, stopping quick at a red light. Otherwise the engine was smooth and started on a dime.

Thanks so much,

John
 
#5 ·
This is why I love this forum! After all these years, I finally learned about JIS screwdrivers. Just bought a couple Vessel (#1 & # 2) from Amazon. I remember many moon ago stripping these screws on my IAC valve. Lots of discussion about this problem on ClubLexus. No one had a clue about JIS screws. Now I can not remember if I replaced my IAC valve screws with hex heads or not. Have to check fast in case I need to cancel order, lol. BTW, Vessel appears to be much higher quality than Hozan.
 
#10 ·
Well this morning something odd came about. Drove all the way to work and as I was pulling into the parking garage, my Ultragauge made a beeping sound and I looked down and it said "Pending code" P0505 but it didn't turn on the CEL. Drove a couple of errands and it did it again. It's not setting the CEL at all. Any idea what the heck I did? We pulled the plug on the IAC, but were not able to pull the unit because I stripped the screw. Odd that the computer is saying "pending code" and I see that code does pertain to the IAC. Other news, so far it's running perfect..The only thing we did was clean the throttle plate and I ran throttle spray down the opening to the IAC with the engine running. Going to make sure the plug is good and snug but I think it is, I recall it clicking.


Thanks guys!
 
#11 ·
Well I may have answered my own question, searching another post of a guy who juiced up his idle speed and got the same code. I noticed yesterday after getting home it was idling too high but forgot to correct it. It's idling in drive at about 1K which I know is too high. Need to back off that stop screw, maybe that is the cause? I guess I'm paranoid that if I lower it back to 700 ish, it's going to act up with the AC on again.
 
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