Higher than normal revs - 2002 9N 1.2 AZQ

[algenon_iii]

Anyone have any thoughts or advice about these two, which may be interlinked (late 2002 Polo 9N with 1.2 12v AZQ engine)?

I've noticed recently that when starting from cold the engine idles faster than it used to (it's around 15-20'c outside so not freezing). Instead of an idle speed of around 750-800rpm the revs are about 1100-1200 (perhaps a bit higher that what I'd get when the AC was on). Once the engine has warmed-up idle goes back down to what I'd consider normal (even when starting the engine). My initial guess is temperature sensor, but could it be a coil problem (or worse).

This one I'm not sure if it's just me but I'm positive the amount the engine revs at when crusing at motorway speeds has crept up and as well as that the engine seems to be sounding rougher under hard acceleration. Perhaps I'm being paranoid but tensioner springs to mind (as well as coils).

I'm thinking about fitting a new set of coils as they're not that expensive from a motor factor and checking the sparkplugs (even though they are less than a year old you can't be sure if the garage set the gaps properly).

TIA

[RUM4MO]

I think that you should think and ask a bit more before spending money of new coils - especially pattern parts as opposed to genuine new VAG supplied ones - you could just end up spending money and adding something more into the equation. Coils causing a faster than normal cold idle, I'd doubt that - keep looking, if it was the temperasture sensor, I'd reckon that the car would either flood or almost flood so splutter into life and have a low rough idle, or end up with a too lean mixture and bog down when asked to move off when cold. Sorry I can't help any more than that, but I sympathise with you now suspecting that its not right "elsewhere" - ie at fast road speeds, its the way our brains run mad!

Checking the plugs is okay bit that would not lead to a high cold idle, ideally the plugs should be NGK and they will have been gapped at the factory.

[blazeguarder]

My car fast idles when it's cold and then slows down when warm same as yours - think it's normal engine behaviour.

And I agree with pattern coils being a bit awful. Had one fitted by the RAC, car ran rougher than normal until replaced with a VW supplied one. More cash but worth it long term.

[tushae]

my engine also does that, on cold starts, idles at 1100 then slowly drops to around, 700-800

[RUM4MO]

I was assuming that the OP's car had just started doing this, ie had normal idle under all conditions prior to now - modern cars do have the ability to control engine revs to a steady constant RPM at idle under all likely conditions, I'm surprised that anyone is having a fast idle when cold - that sort of thing harks back to the "good" old days of carbs with chokes.

[algenon_iii]

@RUM4MO

Thanks for your thoughts on this. You're right in thinking the faster idling has only just started. I've had the car for over 8 years and even in the snow and ice last year it never idled this fast. Normal idle was always around the 750rpm mark and the only times it would idle faster would be when the AC was on (which is understandable).

[tushae]

hmm, update of this, my car used to idle at around 1100, but recent after i started uni, I took my sub out due to the fact i would be doing alot of motorway miles
and I had this sub hooked up directly to the battery and the remote wire on the ACC wire of the stereo, after removing it, i notice the car always idles at around 1000 revs then after it warms up lowers to around 700-800.

[linuxmad]

Sorry to dig this up, but @ algenon_iii, Can you please help me? I have same car, same year and same problem.
Did you manage to sort this out?
Thanks

[john M]

Possibly Crankcase breather valve?.

[Polo called barry]

My polo does the same. Higher idle when starting cold to warm engine up before idle lowers. Normal thing to happen