Please can anyone help

 

My 2006 1.2 polo runs fine but when in traffic idling for a while it wont rev up past idle speed you turn it off and start again and its fine until you idle for a while again . Any ideas?

Any fault lights on the instrument cluster?

Hi no none Its runs really well but after a short tome idling when its hot it just wont rec its like its only firing on 1 cylyder swutch ignition off start after 1 min fine again idles and revs as normal

Edited 13 June, 20215 yr by casper461

If you know someone with a fault code reader, even a basic one, it's probably worth doing that as a starting point. If not, I'd probably take the spark plugs out and see what they look like. Do a search for "reading spark plugs" and you'll get examples of what they are tell you from their appearance. 

 

Have you had any work done recently on the car?

thanks will try it hi no work done

Edited 13 June, 20215 yr by casper461

Have run scanner no faults shown I am wondering if it could be fuel starvation but it is strange you turn engine off and it is fine

It's almost never fuel starvation.

 

Ignition coil on the way out, or exhaust valve starting to burn out would be the top two reasons for a cylinder shutdown on these engines. 

What code reader have you used?

Got a compression tester?

Is it the 6-valve 1.2 variant where the spark plugs and ignition coils are on the front of the head at an angle, or the 12-valve where they go straight down the middle?

 

Hi its the 6 valve and its a nextpeak code reader The car has only done a genuine 26000 miles even though its a 2006 model

Has that code reader ever successfully found a fault code on this car?

I would expect there to be stored codes if a misfire has resulted in a cylinder being shut down.

 

HI no its never been used before problem is i cant be sure anything shut down it was idling well even when it did not want to rev

Edited 13 June, 20215 yr by casper461

Ah, OK, sorry, so it still idles smoothly, just won't come up from idle speed.  

I've not come across that before.  

The reason i mention the fuel is that it is my sons car and its been sitting for a while with hardly any petrol in it i filled it up drove 60 miles and was in a line of traffic when it just would not rev very far and i manged to drive it really slowly off road swithched it off started it again a few mins later and fine I wonder if it wasdirt somewher ein fuel system that was not being pushe through at low revs its very strange.

Does your reader give live information ? if it does I would monitor the G28 & G40 sensor information as I suspect it could be the G28 (crankshaft speed sensor) giving a problem, I seem to recall from the past that if the engine is running above idle speeds and the G28 fails the ECU will rely on the G40 input and continue to operate normally, but if at idle it will not allow any increase in RPM and if the sensor has completely failed it will not allow a start 

No it wont work in live mode

Throttle position sensor maybe.

The insides of the catalytic convertor might have fallen to bits clogging or blocking the exhaust. That would stop it revving well, it would sometimes stall when idling and smell of eggs. You'd probably also hear the rattle of broken pottery inside a can when moving.

 

But it would need severe impact (speed bump strike?) or thermal shock (driving in to a flood when hot?) to damage a cat like that.