Rough Running Wet Rado

[g1ng3r 10]

Looking for a little advice

 

Went out for drive on Sunday and unfortunately ended up going through some standing water and the car immediately starting running rough. Now I let of the throttle instantly so didn't suck in any water but the passenger side of the bay (RHD) got rather wet.

 

During the drive back the car kept running rough and would not allow much load on the engine without misfiring, although would happily rev up with the clutch depressed. I nursed the car home (50 miles), not being able to go much over 2000 rpm with only minimal throttle input, and parked it up for the night.

 

Monday I drove to work and surprisingly it ran alright... until it warmed up and started misfiring again :( The drive home from work was exactly the same, ran fine for 15 mins cruising in traffic until everything came up to temp then misfired again.

 

Today's journey was the same.

 

I am pretty sure it's an electrical issue and related to temperature. I'm planning on checking for codes with vagcom but I can't until Friday unfortunatly.

 

Any ideas which sensor I may have f**ked? :scratch:

Edited September 12, 2017 by g1ng3r

[1200 bandit 10]

Need to know what year and engine you have

[Rado87 10]

VR6? Left hand side of the engine as you look under the bonnet? If so, my guess would be the MAF sensor.

 

 

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[g1ng3r 10]

Sorry. 94 Corrado VR6 (RHD).

 

And no, i'm talking the battery side. I definitely didn't get the intake side of things wet.

Edited September 12, 2017 by g1ng3r

[Rado87 10]

Ah,ok. Opposite side to the MAF then.

 

 

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[g1ng3r 10]

Does the coolant temp sensor (Blue one?) effect fueling?

[Rado87 10]

Was just thinking check the three senders on the stat housing. The blue one gives the ecu a temperature value. The black one does the third stage fan and the yellow does the temp gauge on the dash and the first or second stage fan.

 

 

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[Rado87 10]

Saying that, the new ones I have recently fitted are different colours so that might be different!!

 

 

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[g1ng3r 10]

Cool, I'll order the blue temp sensor now anyway.

[g1ng3r 10]

If the sensor is faulty and misreading, in theory should unplugging the sensor whilst the misfires happen cause it to run smoother?

[Rado87 10]

Not sure to be honest. Maybe unplug it anyway and see if the running issue still rears its head when warm?? There is thread on here called the ultimate cooling guide which contains some good advice. There's a bit on there which says how to test the sensors operation.

 

 

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[Rado87 10]

It says on there that the blue temp sensor has a big effect on fuelling and that the cold running map in the ecu doesn't switch off until water temp reaches 70 degrees.

 

 

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[Jim Bowen 1]

Sounds like coilpack to me. Check it in the dark and look for sparks.

[fendervg 32]

Something similar happened to my VR years ago after driving up a flooded slip road - it turned out to be the O2 sensors underneath the car that had got wet and they needed to be dried out and the wiring cleaned up to fix it.

[Andy T 0]

Ditto check the coilpack, bolted to side of the engine. The plastic usually cracks, flood water will get in there.

 

Can be dried out and sealed with epoxy.

[Dox 23]

The crank sensor is on the front of the engine, check its multi plug for water ingress.

 

If this were mine I'd run the engine at idle with the bonnet open for an hour or so to try and purge any moisture from the multi plugs (you could even unplug them all once hot with the bonnet down for a while to help keep Retain the heat), before re seating the plugs and a test drive.

[g1ng3r 10]

Thanks for the advice guys.

 

Personally, I don't think this is a coil pack issue as surely this would affect running at all times, not just once warm. It also looked bone dry after hitting the water.

 

02 sensor is a good shout as the underneath got soaked!

 

Coolant temp sensor should turn up tomorrow so i'll give that a try, checking for any moisture in plugs as I go.

[Rado87 10]

O2 sensor would make sense. I'm pretty sure it doesn't effect the running/fuelling until the coolant temp is over 70 degrees.

 

 

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[a_riot 0]

The car should run ok even without the O2 sensor and blue temp sensor. Not ideal but shouldn't drive as poorly as you've described I wouldn't think unless there' more than one thing wrong. It does sound like a coil pack issue, perhaps small cracks are expanding when warm and letting water in. If you spray water at it when warm you should see a change, so its an easy, quick test. If you have VAGCOM you can drive while connected and see what readings change and at what temperature when things go south. But it does sound ignition related. Of course, also check all vacuum hoses and replace as needed. If upon getting warm, a vacuum line is allowing extra air in the intake it can bog, run rough etc. Over time the hose gets very hard, and then once warmed starts to expand and allow air in, no longer flexible enough to form a seal. At least that's my theory.

Edited September 15, 2017 by a_riot

[g1ng3r 10]

Replaced the coolant temp sensor last night and did the secondary water pump whilst the coolant was drained (old one had seized). Coolant will turn up today so once refilled i'll take it for a spin and run vagcom.

 

Does anyone have a vacuum line diagram for a VR6 Rado?

[g1ng3r 10]

Good news! It's fixed :smug:

 

It was the Coolant Temp Sensor giving false readings.

 

Now to enjoy the rest of my birthday with a nice cold beer.

 

Cheers guys :cheers:

[Rado87 10]

Spot on. Good to hear it's sorted!

 

 

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