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Onefut

surging issue please help

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Onefut

Hi Folks

My daughter has a 2006 Polo 1.4s 16v auto it developed a problem I can't get to the bottom of

Once started it Idles fine but shortly after it begins surging the revs drop then go back up and it sometimes cuts out but if you blip the throttle to about 3k or more it settles nicely and idles ok for a brief time before being erratic again.
When driving locally it does it constantly and sometime will cut out at junctions, but if you blip the throttle it'll run ok for a time.
On the motorway once you rev passed 3k it goes and will happily pootle along with the revs below that once you've gone passed it one time.
If you give it some gas it'll accelerate roughly till about 3k then clears although on the odd occasion it'll be rough beyond  3k revs.
It does it less when running on higher octane fuel, but does it all the time when running on 95 octane
I changed the MAP sensor and it went away but came back
Throttle has been synced
No codes on VCDS



Any help  gratefully appreciated
 

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vwfan3
19 hours ago, Onefut said:

Hi Folks
Throttle has been synced
Any help  gratefully appreciated
 

Hi

Did you clean the throttle?

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Onefut

cleaned about 5k ago so should be ok

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vwfan3

Hi

In that case I would clean the Air flow sensor with a spray.

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nige8021
49 minutes ago, vwfan3 said:

Hi

In that case I would clean the Air flow sensor with a spray.

What air flow sensor ?? the OP has replaced the MAP/IAT sensor previously 

 

Had similar problem on another members car of the same age a couple of years ago and that ended up with burnt valves as the problem, so I would get a wet & dry compression test done

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vwfan3
On 12/11/2017 at 14:25, Onefut said:

Hi Folks
I changed the MAP sensor and it went away but came back
Any help  gratefully appreciated
 

Hi

How soon did it come back ?

Also, what engine code is it and what is the mileage.

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Onefut

Well I hope it ain't a bloody valve as this is a replacement engine an only had about 55k on it when it went in about 5k ago
Having said that I do have 2 spare heads so while it is a pain it ain't the end of the world


Thanks for your suggestions folks

 

Edited by Onefut

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vwfan3

Hi

Check for any air leaks.

Also replace the tiny diameter (5-8mm) vacuum hoses.

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Onefut

turns out it was a dodgy pre cat lambda sensor

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vwfan3

Thanks for that.

I am coming round to 'planned maintenance' on cars as well.

The lambda sensors should be changed every 50000 miles.

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