Engine cut out in rain. Help!

[Steveyg]

Hey guys.

 

First post but I'll try to be as brief and informative as possible!

Having a real nightmare with my Octavia mkII 1.9tdi ('57, 140k on the clock)
Right so this is ONLY happening in the rain.
When driving engine simply cuts out, no stutter or struggle. Just like turning off the ignition. After a few minutes it will crank over and fire and then run fine. Maybe for 5 seconds, maybe for 20 minutes. I never know!
Took it to the garage after the first time this happened and the diagnostic came up with the Camshaft position sensor error. Camshaft was replaced (along with the cambelt because may as well right?)
Next time in the rain, cuts out. Same as before. All kinds of dash lights flashing sporadically.
Back to the garage and fault codes read. Camshaft position sensor again. The auto electrician was in this time so he checked it out. The camshaft and crankshaft sensors were giving good readings individually but there was a problem with the reference between the two. This turned out to be because the aftermarket camshaft sensor was giving an inverse signal. Replaced for genuine and all reading perfect. This happened to fix the hot start issue by the way!
Next time in the rain, had another problem. This time the car started juddering quite severely, like it was misfiring, after maybe 5 seconds of this the tachometer dropped to zero as if the engine wasn't running, 3 lights came on (Oil pressure, TCS, Preglowing), then juddering stopped and I had power as normal while still showing 0 on tachometer. I don't know how long I could drive like this as I decided to stop as soon as safely possible and shut the engine off for a bit. Couple of minutes later it started straight up no problems and I could finish my journey.
Back to garage, codes read. Crankshaft sensor implausible signal (P0321) and Glow plug cylinder open circuit (Lost the code)
Crankshaft sensor replaced. 

All seems well until about 2 weeks later when I'm in the rain again and the exact same juddering problem occurs as above. Manage to get to work. On the way back, I get the same old cut out from nowhere, pull over and wait a couple of minutes, started up fine, pull away and immediately get the juddering problem exactly the same as the first time. Pull over and wait a couple of minutes, starts fine and gets me home no problem.
Back to garage, fault codes read. Cranshaft implausible (P0321) and Glow plug cylinder 2 open circuit (P161B)
And that's about it really.
During this time we've had the ECU out and checked for any water ingress for which there was no evidence. Sealed it back up, silicon, greased up the plugs. Doesn't appear to be any water hanging about in the windscreen scuttle. We've also checked starter motor wiring looms, checked all visible looms and multi-plugs with no sign of water/damage. Fuse box under the bonnet has been bone dry every time. There are two multi-plugs I've noticed that seem to get water on them. One in front of the fuse box and one behind the passenger side headlight.

 

This always takes between 20-45 minutes to initially happen on a journey and SEEMS to be dependant on the heaviness of the rain. I have been on 30 minute journeys in light rain with no trouble and 20 minute journeys in heavy rain where it's happened. Logically, since it's never happened when the road itself has been relatively dry and it still takes 20-40 minutes into the journey even when the car has been sat in the rain stationary for hours, I have to assume it's water coming up from the road that's causing the issue.

Any ideas? And thanks in advance!

Edited 9 August, 2017 by Steveyg

[Longship]

I'm certainly not an expert, but a google search leads to suspect the crankshaft connector. Could water be getting into that and causing your problems?

[Steveyg]

Hi mate. Thanks for the reply.

 

Could well be, but I'd have assumed that while the crank sensor was being replaced they'd have checked the connection. I will double check though.

 

I would think it's gotta be something maybe just on the outskirts of the sensor since it looks like the sensor itself is sealed up pretty tight in there.

 

Cheers.

[KenONeill]

@Steveyg - I was thinking the same sort of way as well, that is the connections to the crank sensor. I'd suggest checking not just the plug, but continuity testing the wires from there to the ECU as well.

 

Also, does the car still have the OEM undertray?

[Steveyg]

Spoke to mechanic and apparently the connection to the sensor was all good.

I do have the undertray.

I'll see about the wires from the plug to the ECU. 

Cheers! 

[phil5556]

Did you ever get to the bottom of this? I have my dash lit up with multiple lights including oil pressure and no Speedo, revs or temp and a dodgy fuel level.

 

Car seemingly drives ok, albeit with no abs working.

[Steveyg]

I did mate, yes. Should have posted but it was a good while after. Turned out to be water being washed down on top of the ECU and getting into the multi-plug (sat underneath the windscreen scuttle, good job Skoda!) Wound up greasing it to high heaven nad putting it into a freezer bag. 

[phil5556]

Cheers.

I'm about to try and drive it 450 miles home and all being well will try and get the ECU out to dry everything out and take it from there.

 

 

[Steveyg]

Good luck! 
Yeah there wasn't any visible water damage from looking at the ECU, so if you take it out, it may not look like there's anything wrong.

[phil5556]

If I make it back I don't need the car for a few days so can leave the ECU in the warm to make sure it's as dry as I can get it, it's covered in WD40 after a moment of blind optimism, I doubt it'll do anything though!

[Jevpls]

Sounds like mine story :(

Some time ago car on the highway started juddering like starting driving with the 3rd gear. Stopped, turned ignition off, then one - fine. After some kilometers again. Then again. Went to garage and there was some faults in the report (no flashing errors) about crankshaft sensor. The guy suggested to check not the sensor itself but the wiring that usually used to be the case. They said there was one poor wire and they changed it to another one.

After some time another thing started. Sometimes it felt like there is no fuel given to the car (no matter if accelerate or drive calmly). Checked the faults again - some diesel fuel pressure regulator was found to be faulty. Changed it. Unfortunately it appeared after some time again. Then the nastiest thing appeared - problems with throttle actuator. It felt like car is accelerating itself (especially well seen on idle). At this time I had observations that it happens usually when it's wet. Definetely in a rain.

After a bit of nightmare trip when my car stalled like 4 times (had problems with starting it too) then I changed that throttle thing. As you may imagine - no positive result :(

 

So - basically should be wiring or the ECU. Visited one garage to check wiring but the guy said that everything was found to be OK (can't say that the weather was very humid that time - maybe that's  why he didn't found the faulty thing). Visited another one to check the ECU - it was dry and OK... The car had been left in a warm room while the ECU was out so it dried. Then the cold weather came and it was rather dry too. Right now I haven't had a rain for some time and the car works perfectly. Too bad that I don't have the feeling that I can trust it :(

Right now I'm driving as it is and making observations. If the problems appear then I have to visit another garage THE TIME THERE IS A PROBLEM. Otherwise they might not be able to find the problem. Yeah, this timing might be difficult but I don't see any other solution.

 

The garage guy said that nowadays such wiring problems are quite common. Especially with VAG cars.