172 phase 2 over revving erratic idle

[Jordanlewis70]

Hi all I have recently bought a clio sport 172 off a mate, he had a small front end bump nothing major just cracked bumper and bent air con rad and slam panel..
I've changed the panels and changed air con rad! In the process of all this I started the engine and it just goes nuts as if someone's revving it, it doesn't drop below 2000 and just keeps going up and down, I changed the throttle body, pedal, and the two sensors on the inlet manifold, the air con rad is still empty and i was wondering if that is the problem or not.. But i am on the verge of giving up as I need a car asap and this problem is confusing me!! some people have suggested a vacuum.. Some say an idle control valve but i thought the idle was controlled by the ecu and motorised throttle body? As I say I don't know much about it and am putting it out there to pick all you clio sport experts brains! If anyone has a suggestion be my guest... Much appreciated, JPNL.

 

[Shaunkealaher]

Had the same fault when starting my 172 conversion for the first time turned out to be a airlock in the radiator when i bled the system the revs dropped a bit but kept idling high untill it got up to tenperature (not run for 4 months) starts fine now and no over revving

 

[Jordanlewis70]

How do I bleed the radiator? Thanks.

 

[Chip-mk1]

sounds like a throttle body fault TBH

 

[slob]

I have had the exact same problem. It done my head in for ages. I fixed it by tapping the black box bit above the accelerator pedal with the handle of a screwdriver.

Fixed it instantly and has never come back. Still to this day it is my favourite fix of all time!

 

[Ryanph1rs]

Check the inlet manifold start the car and spray some carb cleaner around the join if its got a leak the car will cut out had this happen on a mates as the daft t**t managed to strip 3 of the threads out .... Kids I tell u

 

[bil_liser]

if it has aircon, im assuming you have the compressor unplugged.. is there a feed on the wire requesting it to kick in, as this will advance the ecu a little and fueling under normal operation, it should rev erratically though.

DTC scan i think

 

[Jordanlewis70]

if it has aircon, im assuming you have the compressor unplugged.. is there a feed on the wire requesting it to kick in, as this will advance the ecu a little and fueling under normal operation, it should rev erratically though.

DTC scan i think

Yes it does have air con.. But the air con rad is completely empty due to changing it. Will this make a difference? If so how do I refill the air con rad, thanks!

 

[MicKPM]

A/C request adds around 300rpm on the X65 so this is likely to be either an inlet leak or the ECU isn't seeing something.

When running does the engine respond to any pedal angle or can you plant it and it makes no change to the engines speed? What is the peak rpm on the rev counter?

 

[Deejuk]

Silly question but is this straight after starting or after it is warmed up?

 

[Jordanlewis70]

A/C request adds around 300rpm on the X65 so this is likely to be either an inlet leak or the ECU isn't seeing something.

When running does the engine respond to any pedal angle or can you plant it and it makes no change to the engines speed? What is the peak rpm on the rev counter?

Yes the engine responds to the pedal but the revs don't seem to drop much lower than 2000 it goes up to around 4500 to 5000 highest but it just goes up and down up and down, as soon as I start the car it's revving way way too high, bearing in mind the air con rad is completely empty, thanks