How does the choke work on a Ph1 172

[KitsonRis]

I know how a choke works on an engine! But how does the one on a Ph1 172 operate? Is it like done through the ECU/timing/fuelling? Or is there something mechanical moving something?

Only asking as I am trying to eliminate problems with my sticky throttle. Cleaned all up and it still is sticky. I have detailed the issue in another thread. But basically when you gently lift off the throttle sticks open, but not when you give it a boot full. Also won't do it when the car is off, as if the air going past is forcing/holding it open. When it is stuck open and the car is turned off the butterfly shuts in a "controlled" way and not slams shut.

Just wanting to know how the choke works to see if there is something mechanical that is like holding the butterfly open slightly if the choke is broken/failing.

 

[da rok]

as far as i know its ecm controlled through fueling, there a hot and a cold map... sounds like you have a dirty throttle cable sheath or a weak return spring on the throttle body/ seriously dirty throttle body...

ive had it on older carbed cars where the throttle cable freys inside the sheath causing it to stick...

try disconnecting the cable and actuating the throttle body manually, if that will work... im not sure if the throttle position sensor is on the pedal or the tb on ph1's

 

[KitsonRis]

Brand new cable fitted last week so confident it's not that. Plus does it when actuated by hand. TB was also cleaned last week when when I had it off

If the choke is controlled by fueling and not something moving/mechanical then I am confident the TB is at fault.

 

[Budgie]

Throttle body 100% mate.

They don't have a choke. The ECU adjusts the fueling to suit.

 

[Jekyll]

I wonder if you need a brand new throttle body itself, rather than trying to clean old ones up.

 

[KitsonRis]

I wonder if you need a brand new throttle body itself, rather than trying to clean old ones up.

I will have two now and I am more comofrtble/confident to take one apart to see how it works to replace parts.

Glad its not choke related though. Just wondered how it worked too to try and eliminate problems

 

[Budgie]

I wonder if you need a brand new throttle body itself, rather than trying to clean old ones up.

I remember years ago mine started sticking.

I replaced the spring, sat the lot in brake cleaner and used some fine paper to clean it up. Still didn't fix it.

 

[STEVE.M]

I wonder if you need a brand new throttle body itself, rather than trying to clean old ones up.

Didn`t you have a thread about replacing the Idle control valve (IAC)?

 

[Jekyll]

I did but my issue wasnt this. Mine turned out to be a throttle body gasket in the end.

 

[KitsonRis]

Also this only has to last a year....then its ITB time.

 

[scotiamr2t]

100% the spring in the throttle body. with it fitted look down at the spring an slowly open the throttle by hand, you will see a shiny area on the spring........this is what is causing the sticking. The spring loses tension over time, expands and rubs on the plastic part of the throttle body causing it to stick

Also new Throttle bodies are now obsolete from renault