Problems with cold idle/ high idle when cold

[Andy03]

Evening all looking for a little help with this problem on my 172cup.

I've had this problem for around 6 months now. The symptoms are: car starts fine and idles ok however upon blipping the throttle the revs hold between 1500-2000 rpm before slowly returning to the correct postion. I have also started to notice in the past month that if I'm driving and in gear the car will carry on briefly almost as if it's surging after I come off the throttle

Once the car is up to temp all the symptoms dissappear

my first thought was an air leak but I cannot see anything out of ordinary no cracked of split hoses. I have no engine management faults. I have no idea where to begin with fault finding the throttle body

Any help with this annoying issue would be greatly appreciated

 

[imprezaworks]

Temp sensor.
Clean throttle body.

 

[flebay]

Evening all looking for a little help with this problem on my 172cup.

I've had this problem for around 6 months now. The symptoms are: car starts fine and idles ok however upon blipping the throttle the revs hold between 1500-2000 rpm before slowly returning to the correct postion. I have also started to notice in the past month that if I'm driving and in gear the car will carry on briefly almost as if it's surging after I come off the throttle

Once the car is up to temp all the symptoms dissappear

my first thought was an air leak but I cannot see anything out of ordinary no cracked of split hoses. I have no engine management faults. I have no idea where to begin with fault finding the throttle body

Any help with this annoying issue would be greatly appreciated

Try blocking up the black rubber hose that goes to the inlet manifold down to the acoustic valve, you can leave the pipe on the manifold cut it so you can fit a bolt into the end. The acoustic valve will be permanently open and it wont show when a fault code reader is put on the car.

 

[Andy03]

Air intake temp or coolant temp?

I'll take the throttle body off and give it a clean but does it have a gasket on the inlet plenum side?

 

[bloke]

just rubber ring.

 

[barnesautos]

Air intake temp or coolant temp?

I'll take the throttle body off and give it a clean but does it have a gasket on the inlet plenum side?

Coolant : Approx £18 at the dealers

 

[Andy03]

Try blocking up the black rubber hose that goes to the inlet manifold down to the acoustic valve, you can leave the pipe on the manifold cut it so you can fit a bolt into the end. The acoustic valve will be permanently open and it wont show when a fault code reader is put on the car.

Is that the thin tube coming off the throttle body running down and under the airbox

 

[Andy03]

Cool thanks for the advice so far Ill try what's been suggested so far tomorrow evening

 

[flebay]

Is that the thin tube coming off the throttle body running down and under the airbox

Yes

 

[Andy03]

So cleaned the throttle body last night. I think marginally better. But the issue is still there next I'll change the coolant temp sensor and do the acoustic valve mod

Just wanna check something with the throttle body, when it was disconnected the butterfly valve wasn't fully closed, I cleaned it up, re installed and reconnected it and it was only when the ignition was switched on did the servo start buzzing and the valve moved to the fully closed position. Is this correct?

 

[bloke]

yup.

 

[krappy]

Might sound silly but worth giving the throttle pedal connector a good clean and plug/unplug it a few times as well to ensure clean contact. I had symptoms similar to yours and doing this has solved them.

If it doesn't work it hasn't cost you anything and it is one thing you can rule out before moving onto something else

 

[Andy03]

So got the old man to pop down to europarts this morning for a new temp sensor and there must be something up with their parts catalog as the connector pins are completely different on the new connector

 

[flebay]

So got the old man to pop down to europarts this morning for a new temp sensor and there must be something up with their parts catalog as the connector pins are completely different on the new connector

I would go genuine on that it could cost you more in fuel than the price you save on the part.

 

[Andy03]

How many wires should I have coming off the plug for the coolant sensor. I have two purple and grey

 

[Andy03]

OK new sensor is in. It's still not perfect but it is certainly better. Only rising to 1500Rpm now (where as it was 2000 before) settling back standard cold idle far quicker. Tomorrow I'll cut and bung the pipe leading to the acoustic valve hopefully that will cure it fully.

Massive thank you to everyone who's put forward their advice on this, thank you

 

[Andy03]

OK so this issue is still plaguing my 172 cup.
Does the signal from the input of the throttle pedal route through the uch?

Could a faulty 02 sensor not show a engine management fault
Trying to rule out other possible causes at the moment

 

[bloke]

nope, couple of connectors then to the ecu. you need it plugging in and live data looking at.

lambda can be off and not throw management light on, the clio ecu s a bit of a dumb one in the scheme of things.

 

[Andy03]

Thanks for that buddy. I had my obd wifi module plugged in the other day and saw the ecu was switching between open and closed loop far earlier than I thought it would. I think I'll switch out the first 02 sensor see what that does. I'm thinking the second one is only there to throw an engine management fault