Polo 6R weird idle rhythm and sound

[faggy31]

Hello,
I have been wondering if there is a problem with my car, (1.2 70ps polo 6r). As when i start the engine on a cold start, basically every morning starting the car it idles alright but if i put a little bit of the gas pedal, to around 1500 rpm to 2000 rpm it drops down to around 500 rpm when i let off and will either just hang on or stall.
Also for around 20 seconds max after starting my car there is a squeaking sound from the engine compartment and i would like to know what is causing it.
If anyone could enlighten me on whats wrong if there is any thank you greatly...

[RUM4MO]

The squeaking noise, if you switch on the lights or fan does the squeaking noise get worse, if so it could be the auxiliary belt as the load on the alternator is higher, on that topic, do you think that your battery is okay and getting re-charged okay, ie do you only do long runs or short runs?

I'm not sure why the idle speed should drop too far after the engine speed has been lifted to 1500RPM, maybe someone else will chip in?

Edit:- when were the spark plugs last looked at?

Second Edit:- the squeaking could also be a failing belt tensioner idle pulley, though your car is a bit young for that! Engine Coolant Sensor failure could also cause cold idle problems, I mean incorrect temperature readings not complete failure as that would flag up a failure.

Third Edit(!):- do you have the mechanical knowhow to remove the auxiliary belt, as if so, removing that and starting a cold engine would prove if the noise was coming from something that the auxiliary belt drives.

[faggy31]

Yeah thats what i was thinking, that the car is too young to need a new belt tensioner and they can be expensive to be replaced as I've heard... today i spoke to a mechanic at my local garage and he said it would need a new belt. It has done only 32000 miles tho? Also i have head about chain problems with the 3 cylinder polos, could this be the cause of the revs dropping so low if i put a little gas on when it is cold?
Thank you
Edit: im not sure the last time the spark plugs were checked... Also no the belt has a constant squeak on a cold start wether the lights are on or off etc.

[RUM4MO]

I would have hoped that by 2013 that all the old 1.2 3 cylinder engine problems had been sorted out, so that should exclude chain problems, strange!

[faggy31]

If it would help to figure out whats going on i can try and take a video of the sounds it makes when starting up and the rev problem i am experiencing?

[faggy31]

Hello,
I cleaned the throttle body with some carb cleaner without touching the valve (as it may un-calibrate it) whist my brother was varying the amount of throttle applied to the throttle body to ensure i was able to clean as much as i could (engine off just key turned to ignition).
After this i installed a new air filer as it hadn't been replaced in 32000 miles (since new) reconnected everything back together.
Then I detached the negative battery terminal point and turned the key in the ignition again and switched the headlights on to de-charge all the remaining current in the ecu for a reset and then left it unconnected for 20 mins.
Following the reset i let the car idle until up to operating temp (fan spinning) to re-calibrate idle and then took the car for a 20 min drive at varying speed limits:)
ever since this it has been perfect so far and is an easy fix for anyone experiencing the same problems.

Carb cleaner i used: http://www.eurocarparts.com/ecp/c/Volks ... 0&&cc5_858[/color]

New filter: http://www.eurocarparts.com/ecp/c/Volks ... 62d&000522