Engine response delay

[mikinoz]

I would also give it a good clean and soak it in petrol/clean with carby cleaner then give that a go.

Subaru Upper Cylinder Head treatment is also very good for this.

[Lewi]

I had a bit of time to feel what was wrong with the engine,it seems i was wrong, it isnt so much as a throttle delay as it is the idle problem. It's normal idling rate is at about 800-1000 rpm but every time the throttle is pressed or even just feathered, the rpm dives down below 800 for about 2 seconds the moment the throttle is released before it recovers to it normal idling rate.

[mikinoz]

Is the air conditioner on or off? Sounds like the ISV or a vac leak now for sure.

[Lewi]

Happens both when its on and off if i remembered correctly. Also, i dont know if this helps but there is that buzzing sound that you mentioned when the ignition is on. Im a bit clueless about the digifant system of this engine. The whole concept is a bit new to me so im not very sure about this engine myself.

[rutti]

Hi Lewi,

I just started my 1.8L engine recently (after months of engine work) and noticed the same phenomenon. I have replaced all vacuum lines, so I will be checking my ISV or idle screw (for leaky oring) next. Will keep you updated once i get round to that this weekend.

---------- Post added 06-11-2011 at 10:27 PM ---------- Previous post was 02-11-2011 at 09:04 PM ----------

I swapped another isv which I have cleaned up with carb cleaner today. It's running sweet now!

[Valver.]

Only just noticed this (I often forget to check the Mk2 forum). Sounds very much like the throttle position sensor (TPS). Fairly common failure with ABFs and will throw a fault code in most cases (P0121 IIRC) - do you have the OBD plug wired up? Hope so.

Another part that will cause this problem is ECU relay #30, which can also create intermittent misfiring around 2500-3500 rpm, as well as stalling when coasting to a stop. It's actually worth replacing this regardless, as it's only $33 from VW and will probably fail soon anyway!

Doesn't sound much like a dodgy ISV - they'll tend to create stalling at cold starts or very high base idle when hot if not working correctly. Worth cleaning for good practice, though
Your engine is an OBD2 version FYI.