Heavy Misfire After Rain

Hinamomoko

Hinamomoko

Member
Morning all! I’m new so be gentle.
I couldn’t find a similar thread so starting a new one.

I inadvertently became the owner of a 2001 1.4 AUA while I complete an engine swap on my truck. She’s a little rough but I love her.

Last night we had torrential rain, and now she’s misfiring like no tomorrow.
I’m going to bet the coil pack is toast (I replaced it with a good OE brand a few months ago, so a little frustrating).
I’m going to attempt to dry her out and start her, but worst case, I’ll do coil, HD leads and sparks all together.

My long winded question is, why?! Does anyone else have this problem in heavy rain? What other than the little drain tube do I need to look out for to prevent this happening again. Are they really that delicate that I can’t park drivers side down if the drain tube is clear and flowing?
I’m good with tools but unfamiliar with these little nuggets!

Thanks in advance! :)
 
Welcome to the A2oc!

Possibly the first thing to check is that both the bonnet drain cups are in place (see here for example). They line up with the drain points on the underside of the bonnet but are often missing curtesy of previous owners or ignorant garages.

Then I’d check the seal along the top edge of the bonnet, and around the washer jets as this looks about the right place to drip onto the coil pack of the aua perhaps?

If there is no obvious leaks with water getting where it shouldn’t, then the next step is to get a VCDS scan, there is a free scan register of members happy to do scans if you don’t have VCDS yourself.
(This will give much more accurate clues to what the cause might be, rather than guessing in the dark and changing part after part until the problem goes away)

Hope that’s helpful
Indi
 
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But I’d be surprised if a recently replaced coil pack has failed already due to water ingress as I’d expect it to be a sealed unit.
That being said I don’t have experience with the aua engine, my 1.4 is a bby, which is very similar but with separate coil packs in the spark plug wells.

Probably also worth checking the leads too, I think if these can fail eventually.
 
Hinamomoko said:
Morning all! I’m new so be gentle.
I couldn’t find a similar thread so starting a new one.

I inadvertently became the owner of a 2001 1.4 AUA while I complete an engine swap on my truck. She’s a little rough but I love her.

Last night we had torrential rain, and now she’s misfiring like no tomorrow.
I’m going to bet the coil pack is toast (I replaced it with a good OE brand a few months ago, so a little frustrating).
I’m going to attempt to dry her out and start her, but worst case, I’ll do coil, HD leads and sparks all together.

My long winded question is, why?! Does anyone else have this problem in heavy rain? What other than the little drain tube do I need to look out for to prevent this happening again. Are they really that delicate that I can’t park drivers side down if the drain tube is clear and flowing?
I’m good with tools but unfamiliar with these little nuggets!

Thanks in advance! :)
Click to expand...
Bit long winded, (not unlike me), but water in the under floor compartment, under the carpet, lots of electrical stuff, including the ECU.
If the carpets damp, that's a clue.
Mac.
 
Indi said:
Welcome to the A2oc!

Possibly the first thing to check is that both the bonnet drain cups are in place (see here for example). They line up with the drain points on the underside of the bonnet but are often missing curtesy of previous owners or ignorant garages.

Then I’d check the seal along the top edge of the bonnet, and around the washer jets as this looks about the right place to drip onto the coil pack of the aua perhaps?

If there is no obvious leaks with water getting where it shouldn’t, then the next step is to get a VCDS scan, there is a free scan register of members happy to do scans if you don’t have VCDS yourself.
(This will give much more accurate clues to what the cause might be, rather than guessing in the dark and changing part after part until the problem goes away)

Hope that’s helpful
Indi
Click to expand...
Thank you so much Indi!

I’m still waiting for the rain to stop but looks like I’ll have to suit up and get cracking.
I’ll definitely check the cups as when I bought the car a garage had been in there and failed to secure the crank case breather hose, resulting in the poor girl suffocating and mayonnaise growing in the crankcase breather. So I wouldn’t be surprised if I have some missing bits.
She had new leads, sparks and pack as the leads started to perish. They looked like some very cheap aftermarket replacements.

I’ve managed to get new everything today just in case.

I don’t have VCDS so that’s some amazing information to have! :D
 
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George Hogg said:
If it’s still misfiring take the bonnet off and throw a blackout sheet over you and the engine when it’s running. Get it properly dark in your little tent and look for tracking.
It’s a bit basic but it works.
Click to expand...
That’s a stroke of genius!
I’ve always worked on big diesels so never thought of this.

I’ll black her out this evening and give it a go!
 
PlasticMac said:
Bit long winded, (not unlike me), but water in the under floor compartment, under the carpet, lots of electrical stuff, including the ECU.
If the carpets damp, that's a clue.
Mac.
Click to expand...
Ah sorry, figured more is better lol
She’s dry thank goodness. But when I got her I sealed the sunroof as it was staring to leak, so I’ll double check just in case it’s atmospheric and sitting on the components and there’s corrosion. Thank you! :)
 
Hinamomoko said:
Morning all! I’m new so be gentle.
I couldn’t find a similar thread so starting a new one.

I inadvertently became the owner of a 2001 1.4 AUA while I complete an engine swap on my truck. She’s a little rough but I love her.

Last night we had torrential rain, and now she’s misfiring like no tomorrow.
I’m going to bet the coil pack is toast (I replaced it with a good OE brand a few months ago, so a little frustrating).
I’m going to attempt to dry her out and start her, but worst case, I’ll do coil, HD leads and sparks all together.

My long winded question is, why?! Does anyone else have this problem in heavy rain? What other than the little drain tube do I need to look out for to prevent this happening again. Are they really that delicate that I can’t park drivers side down if the drain tube is clear and flowing?
I’m good with tools but unfamiliar with these little nuggets!

Thanks in advance! :)
Click to expand...
Hi - i had the same issue with my AUA and it was one of the ignition leads had come loose from the coil pack which was allowing moisture in when it rained. The connector had then gone rusty so replaced the coil pack and leads which fixed it. Hope you get it sorted
 
Indi said:
But I’d be surprised if a recently replaced coil pack has failed already due to water ingress as I’d expect it to be a sealed unit.
That being said I don’t have experience with the aua engine, my 1.4 is a bby, which is very similar but with separate coil packs in the spark plug wells.

Probably also worth checking the leads too, I think if these can fail eventually.
Click to expand...

I’ve found the issue! Went to pull the leads and she’s got oil on the sparks. Presuming it’s the rocker/cam cover sealant perishing… and just learned that they’re integral to cam shaft retention. So I’m going to try and tackle that this weekend. But I’m not folding my breath! 🥲
 
Hinamomoko said:
I’ve found the issue! Went to pull the leads and she’s got oil on the sparks. Presuming it’s the rocker/cam cover sealant perishing… and just learned that they’re integral to cam shaft retention. So I’m going to try and tackle that this weekend. But I’m not folding my breath! 🥲
Click to expand...
Good Evening,

But how is this linked to it raining?

Andy
 
Andrew said:
Good Evening,

But how is this linked to it raining?

Andy
Click to expand...
I thought it was rain ingress, but she was parked on a steep slope passenger side up. So I think the oil has seeped though rather than it being wet. :(
Can’t see water ingress in anything. So I can only assume the tilt was too much for the old gasket sealer.
 
Andrew said:
Good Evening,

But how is this linked to it raining?

Andy
Click to expand...
The other thing is that the spark plugs should seal well enough to stop combustion gasses escaping from the cylinders, so oil in the spark plug wells surely wouldn’t be able to get into the cylinders and cause misfires?
 
Hi.

It is not great when your car starts behaving like it is.:(

All the car should do is produce a strong spark that ignites the metered fuel and air.

However, it looks like you are heading in the right direction to get this sorted. What parts did you buy?

Some thoughts....

Could the poor running be put down to a singular small air leakage occurring within the rocker cover gasket?
The 1.4-liter petrol engines sputter when the rocker cover's oil cap is removed.
This issue could potentially be caused by a combination of an air leak and weak spark brought on by the to oil contamination in the spark plug well and the damp conditions.

It would be good to explore what initially caused the presence of oil in the spark plug well.
Has the RTV seal deteriorated with the passage of time, or has it failed at a weak point due to an additional factor?

If the crank case breather and/or cam cover breather are old and partially clogged, pressure equalisation will be less effective, and the rocker cover may be subjected to an increased amount of pressure. This might have been what caused the RTV gasket seal to leak.
I would like to be sure that the leak does not have the potential to reoccur, as removing the timing belt and resealing the rocker cover is a big job. Installing the new breathers (cam cover & crank case) plus any gaskets, hoses, and o-rings would offer further reassurance.

The additional work and costs could limit the scope of your repairs.

Good luck
:)👍
 
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Indi said:
The other thing is that the spark plugs should seal well enough to stop combustion gasses escaping from the cylinders, so oil in the spark plug wells surely wouldn’t be able to get into the cylinders and cause misfires?
Click to expand...
That oil will be hot, volatile compounds, and moisture will end up in the coil pack/plug connections.
Mac.
 
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