UK-POLOS.NET - THE VW Polo Forum

Hello all, hope you are doing okay.
I own a 2004 vw polo 9n and it’s a first hand car. It used to belong to my dad. However this year I noticed that the rpm needle started to drop a bit when coming to a stop and then it jumps back to its usual idle. I remember once it dropped deep down that the engine has started shaking and then it jumped back to its normal idle like nothing happened. (It never stall)
However I cleaned the fuel reservoir with fuel lines and changed the fuel pump with filter. I’ve found one of the injectors has gone bad so I changed it. Changed the lambda sensor the one near the engine. I cleaned the throttle body and the air pressure sensor. I cleaned the air induction kit. (They are all stock. No aftermarket parts) I tested the purge canister valve and it’s working fine.
In conclusion the car is almost brand new now and the performance has became better after all those changes but still I get the rpm needle drop even though it started dropping slightly and very rare after doing a throttle body adaptation with the computer. It felt ok but as I said I still see it sometimes drops slightly than it’s idle. Any help please ?

I had a similar persistent issue with needle dropping, but I was just living with it. Until last week when it developed a misfire, changed the ingnition coil to sort the misfire and it seems the needle drop has now gone. May be worth a check as I picked up a replacement coil for 18 quid from euros.

May not sort your issue, but if it bothers you that much then swapping out the coils for the new one, one by one may tick something else off the list.