S2 Coupe still cutting out at start up.

[orsum]

Below are posts on a fault I am yet to solve.
Please help I need to solve this before I fit the RS2 Upgrades

S2 cutting out at start help needed
12th June 2016, 14:27
My S2 was returned to me yesterday after a long time off the road.

Audi did a full service and I had the petrol tank flushed out, petrol filter and pump changed.

I drove the car for about 10Km pulled up at a body shop, stopped the car and the within a few min started it again.

The car started revs picked up and the just died, the rev counter instantly dropped to zero.

I tried another four times to start the car the same thing happened it kicked in and started to rev then just dies, rev counter dropped to zero. On the fifth attempt it started.

Since then it’s been fine started each time without an issue and I must say running very nice.

The car is standard other than a 044 Bosch pump.

To me it seems like an electrical fault because the way the rev counter just dropped to zero.

Any ideas what could cause this? I don't have a vag machine so I am not sure if there are any codes.

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S2 Messed up after sensor plug was replaced.
30th October 2016, 07:39
Yesterday I was going to collect my car but there were several paint related issues and other more worrying concerns, any pointers as to where to start looking for the other issues will help.

Idle was smooth acceleration was slow like it had no power.

During the five days before collecting the car they said they replaced the battery and replace a sensor plug as it was corroded (not sure which one yet). Apparently the car would start then it would not so an auto Elec checked the car and he replaced a corroded connector. I think they said the cam sensor plug. G40!!!

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7th December 2016, 19:18Feedback

So today I changed the G40 camshaft hall sensor type HKZ101 and replaced it with a Bosch complete with a new bracket.

Started first time

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THE FAULT IS STILL PRESENT 16-09-2017
G28 BRACKET.jpg
So basically I have replaced the Cam sensor with a new Bosch part, I have fitted a new Bosch 044 pump, replaced all the belts, water pump, thermostat, timing belt and bearings and engine mounting.

The car as far as I am concerned is running better than it has ever done so.
The only problem I have is the starting. This needs to be found and fixed before I can start my road trip round Africa.

I turn the ignition key to start the car, its starts. About 1.5 seconds after the car starts and the revs have picked up the rev counter needle drops like you have turned the ignition switch off.

This can happen once and then it will start without stopping or it can take five or more starts before it keeps running.
It does also start the first time and does not stop.
Once started the car runs and does not seem to have any faults.
The only time this fault occures is at start up.

The only code seen is the G28 no signal. Checked by the mechanic that is assisting me with my car. (He is one hour’s drive from my home) I think this was done with the car stopped. He did not clear the code as he was concerned the car would not start again.
I will order a Ross Tech unit today complete with cables. Now I will be able to check the codes myself.

Stripped the G28 and G4 bracket off yesterday and found the bracket had been damaged and glued, is this the intermittent problem? Is the gap on the border line the issue?

To be safe I think I should get a new one.

I checked both the G4 and G28 connection both are clean. Both sensors test the same, the car does run will so I think they are both ok!!

What else can it be?

[orsum]

17-09-2017
Tried to start the car twice each time it cut out after 1.5 seconds.

Third attempt started no problem running well.

[S2TORNADO]

When you start it up have you tried holding the revs at say 2,000-2,500 for 30 seconds or so? The allowing it back to standard idle.

[orsum]

Yep tried that engine picks up revs straight away but after 1 to 1.5 seconds it cuts out.

I have also turned the ignition off and back on again while the engine is stopping the engine kicks back into life the cuts out again 1 to 1.5 seconds later.

It does start normal but then it starts the issue.

When it starts the idle is fine.

Will try to record what happens.

[daren]

Is it something simple like the ignition switch, have you tried moving the key in the barrel while it's running?

[orsum]

Checked the ignition switch wiggled and pulled. And tested with a digital meter. tested ok never cut out while messing with the switch.

Got videos not sure how to post looking into that now.

Trying to load 2 video clips 3mb and 12mb keeps telling me error in loading what an I doing wrong?

[orsum]

Going to loan a scope from work to check the sensors

[Tridac]

Sounds like an intermittent electrical problem. Could be a lose or corroded crimp somewhere on the harness, but I would start by going round all the connectors under the bonnet, unplug, spray with silicon spray and replug. Check the fuse box fuses and relays for corrosion. Unplug all the fuses, silicon spray and change any that have corrosion showing. Same for all the relay and same for all the relays and fuses on the drivers side interior fuse panel. If a car has been laid up for any length of time, damp can get in the the electrics and cause disimilar metal corrosion on contact surfaces. I tend to do all the above once a year, to get the car ready for winter. Eiliminate the simple stuff first...

[orsum]

Will do the connections its good maintenance for a car of this age.

Already replaced the G40 and checked the connections of the G4 and G28.

Next will do the fuel pump relay, Pump has been replaced.

After that I will check the ignition system for the spark plugs. Fit the R8 coil conversion kit and new Bosch spark plugs.

[orsum]

Please check the link it shows exactly what is happening.

https://www.dropbox.com/sh/lcfs9eupc...g0ALYmeYa?dl=0

[Tridac]

Re: The videos. Looks like you are losing all power to everything, including the console, when it cuts out. If you have a test lamp or voltmeter, start by measuring the voltage across the fuel pump relay and see if that remains constant when it cuts out, If not, trace back from there. If that looks ok, do the same on the fuel pump to eliminate the relay, though it could be wiring associated with it. Have you replaced the fuel pump relay and checked the various fuses around that ?. Usually more than one relay of that type, fwir, so try swapping with another as well if you don;t have a spare. The wiring can make it difficult, but if you make a few jumper wires with amp female at one end and male on the other, you can get things like relays out in the open to get a test lamp or meter on to the tags...

[orsum]

Don't use the lights as the indicator. I am turning the ignition on and off.

When the lights on the console go off it is me turning the ignition off when the revs die I turn the ignition back on again to see if it starts again before the engine motion has come to a stop.

[Tridac]

Thanks, my mistake. Just had a look at the schematic and the fuel pump relay is driven directly from the motronic ecu, so have you taken the ecu out and checked the multiway connector for corrosion ?. Silicon spray the connector to make sure, though unless it's had damp ingress, the pins are bright, at least on mine. Then, find some way of getting a voltmeter on the lead form the ecu to the relay, which should stay constant even as the engine dies. If it doesn't then it could be ecu related, or some input to it. The wire to the relay is brown/green and comes from pin 3 of the ecu connector. Would post the schematic, but only have it in .png file format...

[orsum]

I have got a wiring diagram.

Yesterday I received my original Ross Tech cables so I will start with getting the car running clear the codes and start with a clean sheet. Also going to scope the G40, G4 and G28 Sensor,, more over the g40 bit concerned that the new sensor fitted about 3000km ago could have an issue.

I am planning to bridge out the fuel pump relay; before I do I will check for corrosion. Mostly likely I will only have time on Sunday to work on the car.

I am going to do what I call a deep dive on every part I look at. No matter what it is the fuel system or any other part will be under the microscope.

Although it’s a pain having a fault the learning experience is going to be extremely valuable.

[mike74]

does the car have the factory (or aftermarket) immobiliser fitted to it? maybe its something to do with that?