Engine management problems in heavy rain

[Nicepix]

We have had our Octavia II (1.9TD 105) estate for three years, the first two with no problems whatsoever. Last year during a really heavy downpour the car started running rough and some of the warning lights came on. The next day it was slightly better and on day three the problem had resolved itself.

 

A couple of months later the same thing occurred and so I took it into the local Skoda dealer who diagnosed a faulty sensor. That was changed but three months later during another heavy downpour exactly the same fault occurred. The Skoda dealer wanted €80 for a diagnostic to confirm that their repair hadn't fixed the problem and suggested replacing another sensor at an estimated cost of over €400 which I declined.

 

In the meantime Little Wife had trawled the web and found that the source of the problem might be that water from the windscreen / scuttle area is not draining away through the wheelarches. Both inner front wheelarches were removed and cleaned and the channel broddled clear. That was that until today when driving in torrential rain for the first time the same thing happened. The car died at a roundabout, on starting it was reluctant and the following warning lamps came on; Traction control came on steady, Pre-heat flashed, Low Oil flashed and the 'Emissions - Workshop' adviroy keeps flashing. In addition the tacho and cruise control are dead. In the past these work normally once the car has dried out. There is no water ingress into the car that I know of but during today's exprience it did mist up slightly and needed the Full Demist settng to clear it. Also, when I put the car into the garage after driving in rain it does drip out of the wheelarches for quite a while and when I open the driver's door there is some water released from within it.

 

Does anyone know of any trick I've missed or have any suggestions (other than selling the car)?

[Kerans]

I had similar problems with a BKC engined '04 Golf Mk5. In a nutshell I sold the car with a persistent check engine light (not sure on the codes, didn't have VCDS then).

 

I personally think the problem is water damage to the grounding points, loom or the ECU area. I did dismantle the scuttle area completely to expose the ECU - the area was full of leaves, dirt and standing water which I cleared out (and unblocked the two drain channels) and had high hopes of solving the problem but sadly it didn't make a difference. I had the cam position sensor changed by an auto electrician who was convinced it was the problem (made no difference), but I didn't think much of his blind reliance on engine codes (there were so many varied ones, none of which really made sense) - I wanted him to check the wiring loom and the grounds! I didn't have the means to remove the ECU and check it but it had been sitting in water so I have no doubt it had suffered.

 

Good luck with it though - you'll find a fair number of people with similar problems if you google 'Golf Mk5 rain misfire' or 'bkc rain misfire' and similar terms.

Edited 29 January, 2015 by Kerans

[sniper29a]

check all wiring, disconnect ECU...basically, dismantle half of the car ;-) Maybe, you find something.

[Nicepix]

Kerans; thanks for your advice. How easy or difficult is it to dismantle the scuttle in order to clean it out?

[Kerans]

I'm not sure how different the Octavia is to the Mk5 Golf.

 

Here are some guides I used for the Golf - it's actually pretty simple - recommend marking the wipers before you remove them so you get them back on at the same angle but it's quite easy to re-angle them if you get it a little bit wrong. Oh yeah - removing the wipers is a case of waggling with a fair bit of force - I couldn't work it out at first!

 

http://forums.vwvortex.com/showthread.php?4017198

http://www.goapr.co.uk/support/ecu_removal/gti_mk5.html

 

You can then access the whole area and clear it of sludge and water. The drain holes are probably at either end, I used a thin hazel stick to clear them in the absence of anything else suitable. They drain down past the front wheels so if they are blocked and dripping through slowly that could explain the prolonged dripping and the water in your drivers door area?

 

No idea how easy/cheap it is to dry out or repair/replace the ECU if it has been damaged, or even how to tell if it has - I've seen some pics of dismantled ECUs which have clear water damage on the circuit boards inside.

[Nicepix]

Thanks. That is very helpful.

[Nicepix]

Well, all the warning lights are now out and it is running normally. I didn't find that much crud in the gap between the wheelarches so I don't think the problem was there. Although for future reference I have cut a small flap in each side that will allow me to broddle them clear without the hassle of removing the wheels and some screws. 

 

The next step is to remove the scuttle as suggested by Kerans and try and waterproof the EMU unit. I don't get the problem after power washing the car or driving through light or moderate rain. It is only during heavy downpours that it occurs. And then repairs itself after a couple of days of dry weather. I'm convinced that it is down to waterproofing rather than drainage.

[Nicepix]

So here we are again; one year on and the problem not solved. The car has been semi-retired as I got a van for my work and it has barely turned a wheel in the last 12 months. But the other day, in heavy rain the car barely limped home and refused to start for two days. All the usual warning lights were on just as before.  I've tried the main dealers without success. All they want to do is change sensors at €200 - €300 a pop. I can't find a local independent auto-electrician in rural France so, nothing for it but to get under the bonnet. And I am by admission an incompetent!

 

After removing the wipers and the scuttle the first thing I noticed was the lack of crud and wetness inside the bay where the EMU sits. No signs of water ingress of a scale that would have flooded the EMU. The drain holes  allowed water to drained quickly. I have had recently misting up inside the car and whilst we haven't had damp in the foot wells this could be a similar thing to that well known problem. The seal between the scuttle and windscreen was choked with mud inside the ridges of the seal itself. I also noticed that there is a drain hole for the metal tray under the scuttle and VAG have helpfully placed this drain hole right above the ECU and cable that leads to it. My thoughts are that possibly there is a leak between the windscreen and inner moulding allowing water to get into the car and for the mist we see at the bottom of the windscreen. I also think that water coming down the windscreen is finding its way into the metal tray and from there being sprayed over the EMU and cable. Not a lot, but enough to cause the EMU to play up.

 

I have cleaned the mud from the ridges of the seal and lubed it all with grease. After doing that I had the thought of sealing it with clear silicone, but too late for now. I'll see whether the clean and lube works first. I also fashioned a plastic cover for the EMU and put pipe insulation over the cable along the scuttle to prevent it feeding water directly into the EMU.

 

If this doesn't work then I'll have to think about silicone and making a seal around the lower windscreen. Might do that anyway on a drier and warmer day. At least the car is in the garage now and running OK.