VW Polo Erratic Idle

[John2512_00]

Hey all.

My friend has a VW Polo, think its about an N reg.

The Car at idle revs up and down between say 800-3000rpm, and in the past has reved right up to 5000 odd and back down, it some times accelerates or cuts when driving.

Theyve changed the sparks/leads ect, bt want to know anyones experience or oppinions on what this could be, ive done alot of work on older nissans but thats about it, no clue as to how these cars work.

Cheers for any info
J

 

[millerman]

Poss a vacum leak somewhere, can you see any small rubber vac pipes with a split, can you hear a hissing sound?? Try here for more info:
www.clublupo.co.uk

 

[^neo^]

Few things to check:
Air leaks (as MM said)
Idle Stabiliser Valve (some have them some dont, but you dont say what engine)
Coolant temp sender (most likely culprit)
Dirty throttle body

 

[John2512_00]

Hey Guys thanks for the advice,

As I sed Its a mates car but he lives quite a bit away so wont get to see the car for a week or 2, just trying to give him a hand (and learm bout different cars)

Im used to working on turbo'd cars and whenever I hear talk of vaccume pipes I always assume something with turbos, Never realaise naturaly aspirated cars have them to.

Think its a 1lt lump in it but thats about all the info i can get at the moment, so where would the vaccumme pipes be on these?


And the coolant temp sensor, if i were to test it is it an open/shut circuit or should it be reading a vairable resistance? Suppose a sensor like that might be just as easy to be replaced anyway.

Need to get some diagrams of the engine layout on these cars so I can start leaning lol

thanks for the input guys

 

[millerman]

Vacum pipes can be going to/from inlet manifold,cam cover, air intake tubes and various other areas, all cars vary.

 

[^neo^]

full parts catalogue is available on www.vagcat.com and it'll show you how everything goes together. need to register but it's all free.
New temp sender is under 20 quid from VW, probably cheaper from gsf.

 

[John2512_00]

thanks very much for the help, think am gonna order one for his car and fit that n take a look at the vaccumme piping.

If the temperature sender was dodgey, would it affect the temp reading on thedash board or are they likely to be 2 seperate senders?

 

[^neo^]

There are 2 seperate senders.
The one you want is a 2 pin jobby (maybe 4 depending on model), and is usually on the front coolant flange of the head.
It send info to the ecu for fueling............ if engine is cold it needs more fuel / hot engine = less fuel.
When they go the revs usually "hunt" but it's a cheap thing to change and rule out!