Hi, i need to pick some of your brains with a issue on a friends car which im coming stuck with if its allowed.

Im a ford mechanic with 14 years experience but im starting to to run out of ideas il keep the points short

08 polo 1.2 3 cylinder

concern ,poor intermitent start

lacks power plus hesitation.

Basically the vehicle has a cold start issue if start it , its just cranks then eventually fire up idles then splutters and stalls once started again fine then idles fine but has lack  of power and slight hesitation. Usually once warm it starts fine but then sometimes it just wont start.

it was firing up a p0171 code lean fuel code nothing was found with this and

once deleted hasnt returned?

On intital drive its drives as if the cats blocked.

tests carried out valve timing that ok

compression all ok 

parts fitted map sensor plus x2 hego sensors a fuel filter plus a evap sensor.

Ive ran live data but the snap on kit i used is quite basic and didnt high light anything.

I carried a a fuel pressure test yesterday its running at 2.5 bar  i think it should be 3 bar from what i read but it has a 4 bar fuel filter on it so not to sure what the spec is. When revved the fuel pressure drops to 2.4 bar. I did find yesterday when it struggles start a quick spray of wd40 down the intake it starts instanly when it was just cranking. 

Sorry for the long post and not a skoda! I do own two tho! 

Im tempted pull the fuel pump out and see if the filter is blocked. Anybody shed any more light on common issues with these? The car passed its mot yesterday and flew through the emission test. 

Thanks in advance 

 

 

 

Check out the fuel pump and relay.

(Painfully) common problems with these engines/cars include leaky exhaust valves and leaky brake servo hoses, so eliminate the former with another compression test, and the latter by careful visual/manual inspection.

Would also be nice to see live data of coolant temperature sensor info and compare  with reality.

Thanks for the replies, 

regarding the exhaust valves the compression values were all great and  plus it idles well... once its running i have checked these twice now. 

The brake servo hose has no obvious cracks splits etc either. 

Regarding the fuel pump it doesnt make a noise when the ignition is swithched on but when  cranking you hear it work. I am not sure if this is how these work but on the fords they always prime with the ignition on. 

The coolant sensor data was ok all be it my scanner didnt have an option for the one in the radiator. 

Many thanks

I’ve got a 1.2 6v and under @Wino suggestion I did compression tests and they were all fine. It wasn’t till a little further down the line another compression test then showed lower compression on cylinder 3.

 

On mine you hear the the fuel pump come to life as soon as you turn the ignition on. That might be your issue! 

The fuel pump should prime before cranking, something isn't right.

Cheers guys, will look into it further and go from there, 

A leak down check is more effective than a compression test at finding the valve guide issue. 

 

Also check injector flow.