Toyota Repair: 1998 Camry High Idle, accelerator cables, air control valve

Question
Hi Ted,

Thanks once again for the answer.  So I ended up did manage to remove the throttle body and clean the idle air control valve with cleaner.  When I was cleaning the valve I noticed that the valve did not close all the way.  Instead there was a ~1mm gap when disconnected from everything else.  There was also a <1mm gap between the throttle plate and the throttle body when the throttle linkage hit both stopping screws at the same time.  

After I cleaned everything and put everything back together the car would idle normal for the first 1-2 second after starting (1100 cold / 750 warm), but then the idle would increase to 1400 cold/1100 warm over the next minute or so.  I made sure that the throttle valve/cruise control/accelerator cables still have very slight slack when warmed up, it corrected most of the warm idle increase, but the idle still increased to 1400 and drop back to 1000 in pulsing cycles esp when the car goes downhill at 30 - 40 mph without my foot on the throttle.

My questions are:
1) Should there be a gap between the throttle plate and the throttle body?
2) Should there be a gap in the idle air control valve when it is not connected to power source.
3) would incorrect A/T fluid level have caused the increase in idle when warm?
4) What is causing the high idle in general?

Thank you very much again!





















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Followup To
Question -
Hi Ted,

Thanks again for the answer.  I removed the throttle body and cleaned it with cleaner as you said.  However, I couldn't remove the IAC valve without stripping the 4 screws, so I left the valve on and sprayed cleaner through the 2 holes connected to the valve inside the throttle body and the air hose that goes in from the bottom, trying to clean out as much carbon deposit as possible.

Before I cleaned the throttle body the car idled 1400 cold / 1000 warm.  After I reassembled everything, the car now cold idles at about 1000-1100 rpm.  However, as soon as the engine gets warm enough the idle would increase to about 1600 - 1800 rpm for more than 5 minutes.  Then it would settle at about 1400 rpm.  In other words the idle now INCREASES with increasing engine temperature.  As the car idles correctly when cold does that mean the problem is not related with the IAC valve?

Also, I noticed that when i drive down a slope or apply the brakes so that the car tilts slightly forward, the rpm also increase by itself.

It would be great if you could tell me what's wrong with the car as I am trying to sell it as soon as possible before I move out of town.  Btw, is there any way I can remove those 4 screws mounting the IAC valve without a screwdriver?  I dont' have a vice with me so i can't really use vice and plyers.

Thank you very much again!!!!





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Followup To
Question -
Hi Ted,

Thanks for the previous answer.  I am wondering what I should use to clean the IAC Valve.  Some people say that I can use throttle body cleaner, but my Chilton repair menu specifically say that I should NOT use throttle body cleaner for the actual IAC valve itself.  Who should I believe?

Also, may I know what should be the next thing to try if that didn't work?  I am thinking about ECT sensor or TPS.

Thanks again!



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Followup To
Question -
I have a 98 camry 4 cyl LE A/T w 90K miles on it.

It idles at about 1400 cold and 900-1000 warm.  I know the factory spec is ~750.  When A/C kicks in the warm idle dips to 850 then goes to ~900 (lower than no A/C)  as if it were trying to go from 750 to 900 like other cars normally would.

Car starts fine early in the morning, but very intermittently if I drive the car to work then leave it in parking lot (outdoor) for several (most of the time 9) hours then start it again (when ambient temp is warm) the starting idle would be at ~<600.  At this point if I shift into D and drive off then engine idle would jump back to the 1400/1000 pattern.  Instead if I stay in P and tap on the gas couple times the idle would jump to about 2000 (higher than the highest pt reached on a cold start in the morning) then slowly go back to 1000.

Also, when the car is cold there are some suddle clattering noise from the engine (not sure if it was exhaust heat shield rattle or valve train).  The noise is much less prominent when the engine/ambient is hot.  

Couple months ago I just cleaned out the Throttle body.  Don't know if that increased the idle.

It would be great if I could find out what the problem is.  Thank you very much!!
Answer -
The most common problem for erratic idle speeds is the idle speed control valve located on the throttle body, it can be removed from the throttle body and cleaned from all the carbon deposits, this works almost all of the time so give that a try.
Answer -
Yes, use throttle body cleaner and make sure the throttle body is cleaned also again, remove all of the carbon deposits from the bore and the throttle plate.
Answer -
Check the throttle cable and the cruise control cable attachment points and make sure they are not too tight, uou may have to back off the adjustment nuts to create some slack in the cables, one of them may be too tight and is holding the throttle plate open.

Answer
The small gap in the isc valve is normal, the gap in the throttle plate is also normal, as soon as the engine starts vacuum applied to the small dashpot on the throttle body closes the plate all the way at idle.
I'm not sure what the idle fluctiations are caused by but it's not from the isc valve, sometimes low coolant level in the engine can cause this sort of idle change because of erronious  input signal from the engine coolant temp sensor to the ecu, possibly air pockets in the cooling system.