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Old 26th July 2020, 11:08 AM
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Default Help please - car stranded - rain ussue?

Hi

It has rained buckets here today and my 1989 S8 was partially in it. Was under carport but nose sticking out.

Went to take my son back home to his Mother's place. Car started fine. Nothing unusual. Got about 300m up the road and the car seemed to be losing power. Thought it was my big boots pressing on accelerator and brakes at the same time.

Within another 100m the car would not travel any further. Pulled over and stopped the car. Restarted the car but it seemed to be misfiring(?) badly and just would not go anywhere. The transmission seems to select gears properly and I can feel the transmission engage. Car won't go and just wants to stall if I push on the go pedal. Restarted car several more times with the same result. Car seems to be getting fuel OK. Starts straight up every time but will not keep going for more than 10 seconds or so, when it will start to misfire again. I recently replaced the fuel pump so do not think this is the problem.

The ASR and CAT lights are now on - would this be due to the car shaking because of the bad misfiring? (those lights came on when the car misfired when the petrol pump gave up the ghost a few months ago)

The rain gave me pause. I pulled up the passenger side / LHS footwell carpets and there is a bit of water there. Not flooding but there nonetheless. Also, the (masonite?) cover for the relays was a bit damp. Could not see any water in there though when I took it off. Did not spend much time as I had my son to take care of and it was p*ssing down.

Any advice on how to proceed? Please?!
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Old 26th July 2020, 11:34 AM
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Based on what you've said, it sounds like the drains in the plenum chamber are clogged, and the resulting downpour has filled it, with the water overflowing into the car.

Have you ever cleared them before, and have you sealed up Botang's Hole, as I suspect that to be the culprit, with the water coming in the passenger side. Can only suggest you drain off any excess water in the plenum chamber, sort out the drains, remove the carpets in the passenger footwell, as with the rubber backing, they can hold a lot of water.

I'd then suggest something like a dehumidifier in the car if you had one, or maybe just a hairdryer on the wetter areas. Check out the fuse and relay panel while you're down there and dry up as much moisture as possible.

Final thing I would check is the ECU box in the plenum chamber. Open it up and see if there is any water or moisture in it.
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2001 A8 D2 FL 3.7 Q - LPG Conversion, Engine: AKC, Gearbox:FBB, Colour:LY5X Aqua Blue pearl effect, Interior:WJ light beige/dark beige valcona leather with burr walnut inserts

My DIY jobs - Replaced alarm horn, Replaced Coolant Temp sensor, Updated RNS-D firmware, Installed Reversing Camera and Digital TV, Dashcam Installation, Retrofitted Rear Blinds, Auto-Dimming Rear View Mirror, Chrome Boot Struts

Sold! 2008 S8 D3 5.2 V10 - Engine: BSM, Gearbox:KLW, Colour:LY7F Suzuka Grey Pearl Effect, Interior:Black/Black with Silver/Black valcona leather with carbon atlas inserts, Bang & Olufsen, Heated windscreen, Soft-close doors, TV, DAB, AMI, Quad Zone, Auto Boot, Auto dim Mirrors, Keyless entry, PDC with rearview camera, AFS II Headlights

My DIY jobs - Fan Jet Windscreen Washers, Retrofitted Electric Side Blinds
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Old 26th July 2020, 02:28 PM
MikkiJayne MikkiJayne is offline
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That sounds like fuel starvation. How much fuel is in it? Have you run it below 1/4 tank since the pump was replaced?

Do you have VCDS / other code scanner?
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Old 26th July 2020, 02:45 PM
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Quote:
Originally Posted by steamship View Post
Based on what you've said, it sounds like the drains in the plenum chamber are clogged, and the resulting downpour has filled it, with the water overflowing into the car.

Have you ever cleared them before, and have you sealed up Botang's Hole, as I suspect that to be the culprit, with the water coming in the passenger side. Can only suggest you drain off any excess water in the plenum chamber, sort out the drains, remove the carpets in the passenger footwell, as with the rubber backing, they can hold a lot of water.

I'd then suggest something like a dehumidifier in the car if you had one, or maybe just a hairdryer on the wetter areas. Check out the fuse and relay panel while you're down there and dry up as much moisture as possible.

Final thing I would check is the ECU box in the plenum chamber. Open it up and see if there is any water or moisture in it.

Thanks steamship! Yes, I have read about Botangs hole and it is something that I will check. Hoping to get the car back to my place before I do that though. I will check the ECU for water though, in case it could be contributing to the car not wanting to move.
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Old 26th July 2020, 02:51 PM
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Quote:
Originally Posted by MikkiJayne View Post
That sounds like fuel starvation. How much fuel is in it? Have you run it below 1/4 tank since the pump was replaced?

Do you have VCDS / other code scanner?
Thanks MikkiJayne!

Yes, I have run the car to the reserve level more than once since then (carrying petrol with me just in case). The car has been running beautifully since the pump has been replaced. It did seem like it might be a fuel problem, but I was all but discounting that as the car starts strongly. The fuel gauge is just below half way at the moment. I will give it 10 litres in the morning to see if that makes a difference. If the fuel pump relay is wet, could it cause the symptoms that I have described?

I have VCDS but unfortunately my laptop needs power to work as the battery has had it. I only have a cheap cable that is a serial interface and no-one I know has a laptop that old!
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Old 26th July 2020, 03:48 PM
MikkiJayne MikkiJayne is offline
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I'm a bit stumped on that then tbh. I doubt the fuel pump relau could cause that, unless somehow it can't stay turned on and is letting the pump die. Never seen that before though. IIRC its in the bottom of the relay box too so its unlikely to get full of moisture as it drips in from the top so the upper few banks get wet first.

Is the fuel pressure regulator connected?

I can't think of what would cause this which is related to water ingress.
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Old 26th July 2020, 04:27 PM
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Quote:
Originally Posted by MikkiJayne View Post
I'm a bit stumped on that then tbh. I doubt the fuel pump relau could cause that, unless somehow it can't stay turned on and is letting the pump die. Never seen that before though. IIRC its in the bottom of the relay box too so its unlikely to get full of moisture as it drips in from the top so the upper few banks get wet first.

Is the fuel pressure regulator connected?

I can't think of what would cause this which is related to water ingress.
I hope that daylight will reveal more. I also hope that it has stopped raining too!

I will check the fpr.

It is so strange and so sudden. Drove fine the day before. I am only guessing at the water being the cause. Can the ECU having water in it cause this I wonder. I will check that tomorrow.

If I have to have it towed are there any precautions that I should take? Does it need to be on a trailer for example? I have never had to have any of my Audis towed but This might be it if I can't limp it back home. It is less than 1/2 a km away but I am having my doubts that it will drive there under its own steam.
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Old 26th July 2020, 05:35 PM
MikkiJayne MikkiJayne is offline
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You could flat tow it in neutral 1/2 km without any problems. 30km max at <30km/h, otherwise it needs a flat bed. Do not tow it with one axle lifted.

Its unlikely to be a wet ECU - that sits right at the top of the box so its the last to drown. The TCU goes first. Plus the ECU is constructed to be waterproof anyway. The TCU isn't.

If it is rain-induced then Sean's theory about botang's hole dripping in to the relay box is the most likely candidate.
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Old 26th July 2020, 08:11 PM
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I’m hardly an expert - hardly a duffer! - but I had issues a few years ago when my S8 played up in the rain. It went into limp mode, lost power and the had a light show on the dash! After a hell of a long investigation, it was,indeed, water into the ECU in question. Worth a look.
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Old 26th July 2020, 08:24 PM
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Quote:
Originally Posted by MikkiJayne View Post
If it is rain-induced then Sean's theory about botang's hole dripping in to the relay box is the most likely candidate.
I don't know enough about the engines to even hazard a guess, so just omitted commenting on that aspect of it
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2001 A8 D2 FL 3.7 Q - LPG Conversion, Engine: AKC, Gearbox:FBB, Colour:LY5X Aqua Blue pearl effect, Interior:WJ light beige/dark beige valcona leather with burr walnut inserts

My DIY jobs - Replaced alarm horn, Replaced Coolant Temp sensor, Updated RNS-D firmware, Installed Reversing Camera and Digital TV, Dashcam Installation, Retrofitted Rear Blinds, Auto-Dimming Rear View Mirror, Chrome Boot Struts

Sold! 2008 S8 D3 5.2 V10 - Engine: BSM, Gearbox:KLW, Colour:LY7F Suzuka Grey Pearl Effect, Interior:Black/Black with Silver/Black valcona leather with carbon atlas inserts, Bang & Olufsen, Heated windscreen, Soft-close doors, TV, DAB, AMI, Quad Zone, Auto Boot, Auto dim Mirrors, Keyless entry, PDC with rearview camera, AFS II Headlights

My DIY jobs - Fan Jet Windscreen Washers, Retrofitted Electric Side Blinds
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