Audi S2 avant need help.

[Tractor Dave]

I don't think 3-4 seconds is excessive

[psiconauta911]

Filter is new and 3 or 4 seconds isn´t realy excessive but didn´t took that time before and it doesn´t when completly cold or when hot.

[psiconauta911]

Update,

Still haven´t solved it, what´s been done:

Fuel pump ok
injectors ok
temperature sensor on the back of the head ok
Fuel pressure regulator ok
fuel filter ok

Where to look next?

M_GORDON talked about a relay which relay should I look at?

[S2_avant 19930325]

Dont buy things before you know what it is.
If you start the car and it does not run well ,, i think the injectors is overflowing , remove the spark plugs and look at them. If on is wet , then its overflowing or bad spark for some reason.
How have you checked the fuel pressure regulator ?
How have you checked the fuel pump ?
Put a gauge on the fuel rail so you can see the fuelpressure.
Try to check as much you can before buying anything.

Have you put on a boost gauge so you can see what boost pressure you have ?
Have you checked for vaccumleaks ?
Try to spray start fluid around all hoses , and move and shake the hoses a bit while you spraying and the car is running. Some hoses may leak when moved.

[S2_avant 19930325]

what sparkplugs do you have and what is the gap ?

[psiconauta911]

Thanks, the car runs great, I do have a boost gauge and there are no leaks as far as I now, the only problem is that it takes around four seconds on the starter to start when warm but starts fine when completly cold or when hot. Vaccum pipes all recent.
When I say it´s ok I mean it as been replaced by a new item or a new item was experimented before reverting to the one that was there.

[S2_avant 19930325]

Try to start the car when warm. Just before it starts , like ,, 3 seconds. Turn of the ignition and take out the spark plugs. What are the gap on the sparkplugs ? What brand ? How old are they ? You can measure them.

[psiconauta911]

Tha sparkplugs are NGK BKR7EIX with a 0.6mm gap and they are recent as I changed them 6 months ago and don´t have any misfires while driving, so I guess they are good, as for the leaking injectors hipoteses I´ve changed the ones on the car for a refurbished set and it didn´t get worse or better and none of the original or the replacement where leaking.but I´ll do the test you mention just for complete peace of mind, if one or more injector is leaking I´ll get a wet spark plug right?

[K Simmonds]

Yep, if you have a leaky injector, one plug will be very wet.

I've just read this whole thread and have to say I'm a little puzzled, 3 or 4 seconds cranking wouldn't bother me too much to be honest, however the fact it didn't use to do it means something has changed.

All the advice S2_avant gave you is good.

The fuel pump relay is the one with 208 on top of it but I doubt it's anything to do with that.

[S2_avant 19930325]

Hmm isnt there somekind of cold start valve electric thing , so it can help starting when cold ?
What is you water temperature when hot ?
If there is somekind of cold start valve/injector or something like that .. when the car is warm ? Disconnect it and try to start , it can be that its the car is cold so it gets to much fuel for just the start. Worth trying.

[newsh]

There’s no cold start injector on Motronic, you’re thinking of the old mechanical KJetronic.
Motronic controls mixture during warmup by measuring water temperature using the temperature sender on the back of the head, check that it’s reading correctly in Vagcom, also check the wiring plug, mine had the two wires shorting intermittently in the boot, and plug pins for corrosion.
Also the IAT sensor, same checks (Inlet Air Temp sensor on Inlet Manifold.
Once at operating temperature mixture is monitored and corrected using Lambda and MAF.

[psiconauta911]

I´ve changed the sensor on the back of the head for a Bosch one just because the one in there was still the original one and to eliminate one possible cause, I also cheked the wiring an it was ok. I´ll also check visually the IAT and its wiring see if it looks ok, unfortunatly I have no VAGCOM but if you could point me in the direction of a good, user friendly and cheap version I´m seriously considering buying one since it is very pratical for diagnosis also the IAT sensor is still the original from factory, never been changed!

My water temperature it´s normally around 90ºC and the fan works as it should, the reading is usually higher because of the replacement MFTS from Audi but I also control it through the climate control display and it is working as it should I rarelly see it go under 80ºC or more than 94ºC.

[newsh]

I use a very cheap eBay OBD cable with the old free version of Vagcom and 2 into 1 adapter
You’ll need a laptop with windows, I use an old one with Win7.

Something like this, I can email the freeware if it doesn’t come with.

[psiconauta911]

I use a very cheap eBay OBD cable with the old free version of Vagcom and 2 into 1 adapter
You’ll need a laptop with windows, I use an old one with Win7.

Something like this, I can email the freeware if it doesn’t come with.

Thanks mate!

[psiconauta911]

So removed the IAT sensor and was 28 years old dirty, kind of gold on the buterfly side and completly black on the engine side, giveit a good clean with contact cleaner and lightly scrub it with a ear bud, it turned out great, very clean and gold coloured, instaled back and no changes, also cheked the wires at the plug and they are ok, also cleaned the contacts. I´m yet to do the test of removing the plugs I´ll be back after that.