Camry Idle speed

[toyota1971]

I have a problem in my camry.when i start the car first thing in the morning poor cold stat idle.Engine RPM surging between 800-1000RPM.Cleaned the IAC valve and throttle body reset ECU by disconnecting the battery negative cable.After done this car was ok for few days and the same problem return.
Check ECT ,IAT sensors all ok.(Also replaced the ECT sensor with OEM part later on and didnt fix the problem.)
swapped the electrical solenoid for IAC valve still the same.
When car is warmed up all seems to be ok.Only problem is no cold fast idle,
I warmed up the car to the operating temperature removed the ECU and placed in the freezer for 15mintes,installed back to the car and idle speed played up straight away.This time worse than ever,so carefully heat up the ECU with a hair dryer and idle speed came good again,This did for three times and confirmed the malfunction was in the ECU.
Replace the ECU and fixed the cold start idle issue.After 2 weeks problem seems to be coming back but not bad as before.
Now on cold start up engine speed sitting around 900-1000RPM.(With the old ECU idle speed was hunting badly between 800-1000.)
Why cold start idle speed not sitting at 1500-1200RPM as it used to in the past 7 years?
I took my car to a Toyota dealer they checked the engine management system with Toyota scan tool and couldn't find any thing wrong.

[Mister_Perkins]

You said you cleaned the IACV. Did you pull it completely off and thoroughly clean the Valve.. making sure it turned all the way to the left, all the way to the right with no problems at all? Did you clean the EGR too? It could be stuck partially with carbon on the Valve Side. Remove it and push a screw driver inside the top section that bolts up with the two 12mm bolts and see if it moves freely. I suspect some carbon will drop out of it. There really isn't a whole lot that the Toyota Break out Box and scan tool can detect on OBD1 .. A lot of times the ECU wont even detect a problem if its there.

[toyota1971]

Hi Mate.
Yes i did remove the IAC out of the throttle body and cleaned it very well but no luck.
Cheers.
Bob.

[toyota1971]

Mmmm where are the others?

[Stillrunning]

Originally Posted by Mister_Perkins

Did you clean the EGR too? It could be stuck partially with carbon on the Valve Side.

Did you check this?

Originally Posted by toyota1971

Mmmm where are the others?

I'd look for vacuum leaks (as above) at this point. Which would also include PCV. No magic solutions answers.

[toyota1971]

Originally Posted by Stillrunning

Did you check this?

Yes i did and seems to be nice and clean.



I'd look for vacuum leaks (as above) at this point. Which would also include PCV. No magic solutions answers.

Couldn't pinpoint any vacuum leaks.Car runs fine.

[Stillrunning]

Originally Posted by toyota1971

Replace the ECU and fixed the cold start idle issue.After 2 weeks problem seems to be coming back but not bad as before.

Kinda makes it confusing. What year is this Camry? Did you replace with used ECU? Not sure about AU but here there are companies that test and repair ECUs for a fraction of replacement cost. If you open the ECU you may see something like burning capacitor(s). Or it may be a grounding issue. You could find/clean as many ground connections as possible.

[toyota1971]

2001 model.Second hand ECU from wreckers.
Before i install the second hand ECU i placed it in the freezer for half an hour and it didnt play up as the original ECU.Definitely the Original/Factory ECU has a problem.As ECU getting colder the engine idle speed hunting badly.Replacement ECU didn't play up after i installed it.But after a week engine cold start up idle speed dropped to 1000RPM from 1400RPM.Don't know why.But now car is running 100% better except cold start idle speed is lower than before.Apart from low cold start idle speed everything else ok.

[toyota1971]

Hi Guys.
At last found the problem,It was defective Throttle position sensor.Replaced the sensor all ok.Now engine cold start idle speed sitting around 1400RPM.
Cheers.
Bob.