Help to fix the intermittent high idle

[andy_4759]

Hi there 

i have a Toyota corolla ascent sport auto 2014, when i'm driving and slowing down i feel the idle is too high and when i stop completely the idle is around 1500 RPM then in about 5 seconds it drops back to its normal reading 750 RPM .

the car drives very well with no vibration or interruption at all.

when the car is in park mode and raved  1-2 -3 -4 000 RPM and let go of the peddle it drops back to 750 with no issue, it happens only when im driving

Can someone please help to give me hints and what to try, the OBDII showed no errors 

 

Regards 

Andy

[campbeam]

I would be inclined to check/clean the air filter, Mass Airflow sensor [MAF], throttle body and Idle Air Control [IAC] valve.

Following video shows how to remove the throttle body and then do the cleaning.  Instead of doing this, I use throttle body cleaner on a rag to clean the opening especially around the throttle valve. I also spray the cleaner into the opening/passageway of the throttle body leading to the IAC valve. 

 

[andy_4759]

Thanks you very much for your reply, i'll give it a go this Saturday and let you know.

Regards 

Andy 

[campbeam]

Another thought would be to lubricate the accelerator cable with some silicone spray, if there is one on your model Corolla.

Something else for future consideration is to change the automatic transmission fluid, if that has not already been done.

[SRA]

How's the temperature gauge when that happens? Does it point below the middle during high idle? could be a stuck open thermostat or a worn thermostat seal, they are both very easy to replace.

[AurionX2]

Manual or auto? If CVT, maybe that's the nature of the beast. I noticed similar behaviour on a 2016 CVT Pulsar I drove for 3-4 days a couple of years back. How long you had the Corolla for? Have you driven other 2014-2016 Corollas to draw some comparison?

[andy_4759]

Thank you all for valuable hints you are giving me to narrow down the issue and i do appreciate all your feedback.

 

• This Corolla 2014 ascent sport has electric throttle and has no cable, i'm planning this Saturday to remove the throttle body and give it a good clean.
• In regards to the temperature gauge  it is just a tiny fraction below middle when the car is warmed up.
• It is a CVT auto and i  had it for about 6 months and driving by my kid, i will try to find someone at work with similar model and compare. 

Thank you all for your help.

Regards 

Andy

[andy_4759]

I have removed the throttle body and seems reasonably clean, but i cleaned it with throttle cleaner including the circumferences where the flap touches the body of the throttle.

The throttle position sensor is not replaceable as it is riveted and no screws to undo it, it seems is sold as complete assembly.

I noticed the throttle flap is a bit open less the half a millimetre, Please see the photos and advise if this is normal.

Once assembled and brought up to car normal operating temperature, i took it for a drive and i come to a complete stop the RPM is sticking between 900 and 1000 and not dropping down, before cleaning it was sticking on 1500 then drops to 750RPM.

should i drive it for couple of days to see if changes back ? your recommendations are much appreciated.

Regards 

Andy