my brothers just got a new car as his girlfriend upgraded due to hers having a fault on it.

its idleing funny, bouncing up and down from about 1800 to 2200.
its had a new throttle body on it and that didnt fix it.
there is an 8 pin plug on the side of the throttle body that i think is a choke of some description.

when that is unplugged it idles ok.
i took the air filter and housing out the way and with the plug connected you can see the butterfly valve open and close slightly with the idle. if i hold it down it helps but its being driven by a motor so i cant hold it fully closed.

also if you start the car with this plug out and plug it in once running it dosent cause it to idel funny.

today we changed the colant temp sensor and that didnt change anything.
we changed the plugs and they come out very black so it does seam something is causing it to run rich and idle strange.

anyone got any other ideas on what could cause the choke to kick in and cause these problems?

 

idle control valve and carbon build up?

If it is running rich maybe this has lead to a carbon build up meaning the valve isn't functioning?

Mates cossie used to suffer, unplugg it and it ran fine, but then when started from cold it would cut out as there was no choke iirc? Cleaned it all out and it was fine for a time.

Also had a pug with the same problem, unplugged the idle control valve and rev dropped to normal.

 

is it fly by wire throttle if so possible pedal sensor have you had it on diagnostics???

 

havnt found the idle control valve yet. will keep looking.

its not fly by wire, quite an old one, about an r reg.

 

air leaks are common.servo pipe etc.

unplugging sensors proves nothing.as it will go into limp home, and/or mask any other faults anyway.


try carb cleaner down the t/b, this normally works its way into the iscv.

 

Ive been looking for air leaks, but havnt found much looking dodgy yet.
tempted to change the inlet manifold gasket incase.

i'll get some carb cleaner and give it a good spray also.

It just seamed strange that this plug effects the way it idles so much and also im pretty sure it is what controls the butterfly valve in the TB and like i said you can see that moving about with the revs.

 

dropped it to a garage today, they set up the new throttle body with the ecu and it fixed the problem.

drove it home (only a mile or 2 round the corner) and it started to hunt again but not as bad, between about 1100 and 1300 rpm.

went back out and started it again a few hours later and it was doing as it was at first from around 1800 and 2200 rpm.

any one got any ideas because im confused now.

 

anyone?
i feel quite sorry for him, was so haooy when it worked, 2 minutes later was broke again.

 

The Idle valve is built into the throttle body. And don't push against the motor on the flap. It's an expensive mistake

Any faults recorded? Also did they erase learned values before running basic settings. Did it say "ADP OK" afterwards? Is the throttle valve clean inside?

Inlet gaskets can go. But rare. Brake servo pipes used to crack, there was a recall so I'm sure it will have been done by now.

Does sound like the throttle body though.

Quick thing is the throttle cable too tight? That can mess it about but again its rare.

Next thing would be a compression check. Oh and make sure the ignition timings OK. Probably is, but can't hurt.

I've had a Polo doing this to me a long time ago, can't remember what we did in the end. Probably just disconnected the battery for 20 mins