Rough idle when AC on (T27 1.8 petrol)

[TOYOpeter]

Hi all,

Coming from a Lexus Hybrid and recently purchased a used Avensis T27 petrol 1.8, I am not sure if this is normal, because a hybrid is completely silent so no vibrations and in EV mode).

When I start the car and engine is cold, the needle is moving up and down. 

I have made a video. The engine here is warmed up. I tested in park and drive mode, turned AC on and off. When AC is off the needle barely moves. Skip to 3:00, here it is in DRIVE mode and AC on. 

 

Should I be worried? So far I only plugged in a OBD scanner and started Torque app, but no codes. Nothing else checked yet because weather sucks these days.

 

[stantheman1]

Does your scanner show when the last time the codes were reset? They may be still there in the history if its had any.

Does the compressor sound noisy in operation?

Check the tightness of the Battery terminals and that they are not corroded. 

Also check the belt tension.

[TOYOpeter]

On 10/30/2020 at 4:21 PM, stantheman1 said:

Does your scanner show when the last time the codes were reset? They may be still there in the history if its had any.

Does the compressor sound noisy in operation?

Check the tightness of the battery terminals and that they are not corroded. 

Also check the belt tension.

Checked, all seems fine. Not sure if torque stores codes, unfortunately I could not find any.

Next thing im going to try is clean the throttle body and use an additive. It wont be any time soon because I dont have a nice place to work om the car at this moment.

Will update when I have done cleaning the TB

[stantheman1]

👍

[yossarian247]

Does the raising and lowering of revs coincide with the duty cycle of the AC compressor cutting in and out? You should be able to see under the bonnet as when the AC compressor is running the cooling fans should run at the same time. If so it's normal and it's how the climate control system regulates its output. Each time the compressor cuts in the engine ECU increases revs slightly to compensate for the additional load. My 1.6 Valvematic Auris did this all the years I owned it and its nothing to worry about. 

[TOYOpeter]

@yossarian247 I'm not sure if you can see it in the video, but it seems to also happen when the AC is off. What I find the most annoying is, is that when I am driving at low speeds below 60km/h and I am pressing the gas pedal lightly to maintain the speed, the RPM is around 1000 RPM. When it is just above 1000RPM, all is fine, but usually it drops just below 1000, this causes the engine to vibrate and you hear this low bass "brrrrrr" sound. The engine won't stall and when I press the gas it picks up nicely. 

At higher speeds the RPM is higher and I don't have any issues.

 

I am still planning to clean the throttle body, replace the PCV valve, clean the MAF sensor and add some fuel additive in the tank.

 

Does anyone know the part number of the PCV valve and the intake manifold gasket? The PCV valve is hidden away in this engine and when removing the intake manifold, I will also replace the gasket.

I still don't have the time and space to work on my car, but I am preparing all the parts needed to do the job.

 

[mrfixer]

Your engine uses the Valvematic system to control valve lift and valve timing. It doesn't have a conventional throttle plate or 'throttle body'.

Idle speed is stabilised by the ECU controlling valve lift, valve timing and spark timing. I doubt you can easily improve the situation. Wear in the Valvematic mechanism might be the problem here.

[yossarian247]

On 11/19/2020 at 12:55 PM, TOYOpeter said:

@yossarian247 I'm not sure if you can see it in the video, but it seems to also happen when the AC is off. What I find the most annoying is, is that when I am driving at low speeds below 60km/h and I am pressing the gas pedal lightly to maintain the speed, the RPM is around 1000 RPM. When it is just above 1000RPM, all is fine, but usually it drops just below 1000, this causes the engine to vibrate and you hear this low bass "brrrrrr" sound. The engine won't stall and when I press the gas it picks up nicely. 

 

 

Mine always did that if I let the revs drop too low then tried to accelerate hard. It's difficult to know without actually driving the car, but everything you've described sounds normal for a Valvematic engine to me. Of course mine could have been faulty!, but I owned it for 6 years and took it from 30k to over 110k and the characteristics of the engine never changed in that time. It is an engine that needs to be revved, in common with many 16V petrol engines it hasn't got much low down torque.

 

 

[TOYOpeter]

I have cleaned the throttle body and it has fixed the low idle issue.

Since then I noticed that the car running at low rpm when I maintain speeds up to 50km/u. I will create a new thread for this