Sorry to bring in another car problem thread…

My 51 reg seat leon 1.6 petrol has problems,
once warm and coming to a halt, upon dipping the clutch the revs will completely drop, often to around 1-200rpm, then bounce back up and down for a few seconds. Sometimes it will stall completely.

Normal driving is fine, just upon idle it starts ‘hunting’.

very intermittent (not done it today).

plugged my cheapo diagnostic thing in, got “system running lean” .

done some research and sounds like it could be a vacuum leak – question is how do i know which are the vacuum pipes and how do i safely check them?

all help appreciated!

First one to check would be the brake servo vacuum pipe. They’ve a bad habit of splitting on that vintage. Can give you more details if you’re not sure where to look.

bouncy idle and stalling

Sounds like my ex missus

Do you know anyone with VCDS/VAG-COM?

As above with the servo, vac pipes, breaks in the inlet pipe after the MAF (I think they run a MAF on the 1.6)

Sounds like a vacuum leak to me. Owners forum will tell you where the usual failure point is.

M0rk will be along soon with a definitive answer, my guess would be map sensor.

Or sticky idle valve (assuming it has one) drown it in brake cleaner and shove it back on.

My old 1.8 20VT Leon had a very similar prob with “hunting” revs in idle down to an almost stall (older model/different engine size so quite possibly not relevant disclaimer!)….. Drove ok otherwise but eventually started feeling like missing a bit when accelerating in 5th/6th at motorway speeds. Eventually started stalling at lights etc. All of the above forum suggestions examined by a very good and thorough mechanic with access to diagnostics but cause was still not clear. After checking MAF, coil and vacuum possibilities, he tried cleaning the throttle body but no change. Sourced a 2nd hand throttle body (Seat dealership wanted obscene amount for a new one) and she was as good as new again. One option to consider at least. Hope that’s helpful….I spent ages searching forums and none recommended this.

cleaning the throttle body sorted ms maccruiskeen’s 1.4 leon that was behaving in a similar manor

Clean throttle body and have basic setting reset with decent diagnostic equipment .