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Hi, I have a 2003 1.2 petrol 9N Polo. I am really struggling with a cold starting problem. When I come to start it from cold, it cranks over quite happily, but takes many turns of the key before it catches- it sounds like it’s coughing and spluttering before it finally starts. Once warm, it runs great and I can stop/start fine. I have changed all three coil packs and checked the spark plugs, and the plugs aren’t that old (but look v oiled). I cleaned the plugs with a blow torch and it started first time. I have also replaced the water temp sensor, but that didn’t make any difference (though I am worrying if the non-Oem sensor that I bought could have been defective?). I’m running out of things to check or replace. Any ideas/

Did you have a look at the air mass meter on the inlet plenum?

It might need clean or replace. You can disconnect and see how it starts/runes (it would be a bit lumpy on a default fuel map)

If the plugs are all very oily then the valve guides will be worn, a common issue with that engine when it has lots of miles under its belt, if you check the compression you will probably find that it is a lot lower than when at a lower mileage. The easiest fix is normally to buy the cylinder head from a lower mileage engine and swop heads.

Might also be a faulty PCV or a crack in one of its lines.

the faulty PCV valve idea is interesting - Im going to look into that - and will report back. I don't think its the valves as it runs really sweetly when its up to speed..? Is it easy to diagnose / test the PCV valve?
Jonathan

jonnow wrote: Tue Oct 05, 2021 9:40 pm the faulty PCV valve idea is interesting - Im going to look into that - and will report back. I don't think its the valves as it runs really sweetly when its up to speed..? Is it easy to diagnose / test the PCV valve?
Jonathan

This may help. Search in file for Crankcase Breather or Diaphragm valve.
There is a non return valve in the air intake line to this diaphragm valve so relatively easy to check but don't think this is your problem.

http://www.volkspage.net/technik/ssp/ssp/SSP_263_d1.pdf

Johntheo1 wrote: Wed Oct 06, 2021 7:24 am

jonnow wrote: Tue Oct 05, 2021 9:40 pm the faulty PCV valve idea is interesting - Im going to look into that - and will report back. I don't think its the valves as it runs really sweetly when its up to speed..? Is it easy to diagnose / test the PCV valve?
Jonathan

This may help. Search in file for Crankcase Breather or Diaphragm valve.
There is a non return valve in the air intake line to this diaphragm valve so relatively easy to check but don't think this is your problem.

http://www.volkspage.net/technik/ssp/ssp/SSP_263_d1.pdf

Good tip! Make sure you check the EGR as well. The valve could be faulty or the piping could be clogged. This system gives the engine more air when cold, so this might explain why it runs rough when cold and fine when warm. So it needs to be clean

Strangely, there is usually a similar problem with spark plugs. If you have checked everything, then perhaps you should check a whole complex of devices - an electric or mechanical gas pump, an injector or carburetor, a filter, and fuel lines. Perhaps a bad gas mixture or gasoline does not mix well in the air. Most likely the problem is in the fuel system, you can also look at the air intake, maybe it is dirty. I had a similar problem with the Dodge, I had to change the air intake well and there are https://nashvilleperformance.com/cold-a ... 6-duramax/ many options Best Cold Air Intake for 6.6 Duramax for replacement.