Do i Have an Engine Management Light? Erratic Idling?

[H17E5H]

Hi,

I recently bought a 1998 Audi A3 for my other half as a get to and from. However, when the car is idle-ing the rev counter starts to fluctuate between 800-1000rpm and a couple of times it has sounded like it is about to cut out. I've given it a full service including all filters (air, fuel etc) and spark plugs (NGK), thinking a good service would rectify most of the problem i.e having no restriction in air or fuel and having decent spark plugs for good ignition, however the problems still continues and is sometimes very noticable once the engine is at operating temperature. I've spoken to a few people including techies who said it could be the air flow meter so i replaced it with a original Audi air flow meter only to discover the fault still exists.
A friend had it put on a diagnostic machine for me but no faults existed in the engine section. I then quired if my vehicle would have a engine managment light but no one knew so we disconnect the air mass sensor and camshaft postion sensor hoping this would bring on the light but no light showed?

Just wondering if my vehicle has a Engine Management Light and what could be the cause of the idling problem? The car has one of the earlier instrument clusters without the LCD drive information system (DIS).

Thanks.

[Teutonic_Tamer]

VAG motors seem to be a little picky about spark plugs. Try fitting some correct spec OEM Bosch plugs.

[H17E5H]

Thanks for the advice.

Bought original Audi spark plugs from main stealers but problem still exists, slightly more erratic idling than before.

[Teutonic_Tamer]

Righty - you didn't actually state which engine it is, but, being as they seem to be the most popular, I'll guess at the 1.8 turbo 20 valve - though please correct me if I'm wrong!

OK, you state that the idling seems worse after you changed the plugs again. Try and track-back through your work - thinking about what was removed/disturbed, during the plug change. I have a hunch that there might be a small air leak somewhere, either in the crankcase breather system, or in the actual main air intake system. Check all visible rubber hoses for signs of perishing and cracking. Try to flex and "squidge" the hoses as the engine is idling, to see if it makes any difference.

How many miles has it done?

Did you change the fuel filter - whoops, you did! doh! Do you still have the old filter? If so, can you actually "breathe" through it - does it feel blocked at all?

What fuel do you use?

Engine management light - yes, all cars (petrol) from about 1990 have one (though the early ones did monitor for less parameters). Does it not describe this in the owners manual?

What kind of "diagnostic machine" was used? Realistically, only the main stealer VAS5050/5052, or VAG-COM, along with some of the very expensive independent dealer kit, such as certain Snap-on or Bosch KTS can actually read the "proper" manufacturer specific fault codes - and without these codes - you will end up replacing unnecessary components.

[a8 tech]

Remove and clean throttle body,carry out basic setting 60 or 98.Check if any additional signals interrupting idle signal ie fans or p.A.S switch

[jonallport]

A8 Tech has it!

Clean the throttle body - may be more problematic that first thought as some engines (like my 1.6 8v) have the throttle so-placed right against the firewall/bulkhead - drat!