2016 Audi Q3 2.0 - Rough Cold Start

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Good morning, gents.

I have not looked at this vehicle yet, so I'm relying on the information provided to me.

My neighbor is experiencing a rough start on cold start only. The car turns over, but does so "roughly". Subsequent starts are without a hitch, unless the vehicle has sat for a while. I immediately thought perhaps she has a leaking injector, but according to her, the shop (not sure if it's the dealer or indy) tested them and found nothing abnormal. They did find that cylinders 2 and 4 are showing an occasional misfire (no CEL though), they swapped plugs and coil packs between cylinders and found no difference. I'm not entirely sure what all they did to remedy outside of a fuel system cleaning (imagine that...) but she paid them a cool $1k for a fix that didn't fix the issue. She did acknowledge that the problem did subside for a little bit after the shop visit, but has returned to its original state (a few weeks have gone by) and wants to find the fix rather than continue driving it like it is. I'd like to give he a hand, but my schedule is packed for the foreseeable future so at the least I can do some online investigating for the time being.

Where would you start to troubleshoot the issue?
 
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Only codes that have pulled are the misfire. I need to look at the documentation she received from the shop to see if they walnut blasted or not.
I have a feeling that there are more faults. Did you scan with a tool that is capable of pulling the OEM fault codes? By rough start, do you mean long crank, or rough idle after it starts?
 

RamFan

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First thing I thought of also (CBU). How many miles on it? And what year?
Not sure on mileage. I'd anticipate in the 60-80k area. It's a 2016.
I have a feeling that there are more faults. Did you scan with a tool that is capable of pulling the OEM fault codes? By rough start, do you mean long crank, or rough idle after it starts?
I have yet to look at or touch the car, this is based off her description and what the shop did. Based on her description it seems to be more of a long crank condition. I'm hoping to get some more information today and possibly a few minutes to poke around.
 

RamFan

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Alrighty - A bit more information.

Car has 83,000 on it, and I was wrong in my initial statement about it being a long crank. It is more of a rough idle issue, no delay in start. Normally just when the vehicle is in park, after a few minutes it settles down on its own. Based on the service invoice, below is what was completed and stated.

Tech found oil separator (I'm assuming PCV?) faulty causing excessive crankcase pressure. After separator was replaced, the tech was able to duplicate misfire in cylinders 2, 3, and 4.

Intake valves "very carbon covered and cause of the misfires", intake manifold removed and intake valves manually cleaned.
 
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$1K for that work is actually a very good price. Usually it is around $1500 for the valve cleaning alone plus a few hundred for the PCV.

Just to confirm, the issue is still unresolved? It is possible that the valves were not cleaned well enough. Have the plugs been replaced?

 

RamFan

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Correct, issue improved for a little bit (few days/weeks) but has returned. Plugs were not replaced.

I’m thinking for a simple step I’ll swap out her plugs, put some Berryman or Techron in the tank, and perform an induction cleaning (probably CRC) and see if that causes a temporary improvement at minimum.
 
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Correct, issue improved for a little bit (few days/weeks) but has returned. Plugs were not replaced.

I’m thinking for a simple step I’ll swap out her plugs, put some Berryman or Techron in the tank, and perform an induction cleaning (probably CRC) and see if that causes a temporary improvement at minimum.
I'd do the plugs, but skip the snake oil. If the induction cleaner pools in the intake, you may hydrolock it.

Remove the coils while the engine is still hot - they will come out a lot easier. I would scan the car with the proper tool; I have a feeling that you have more than just misfire codes.
 
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I had a rough idle on start on my '02 Taurus that I shrugged off for a few years. It would smooth out after a minute and be fine until it sat for a while again. It finally got to where it would not go away after the car warmed up. It was a slightly blown head gasket. One broken trace on that goofy Fel-Pro gasket with the silly orange traces around the coolant ports - #1 cylinder.
 

RamFan

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I'd do the plugs, but skip the snake oil. If the induction cleaner pools in the intake, you may hydrolock it.

Remove the coils while the engine is still hot - they will come out a lot easier. I would scan the car with the proper tool; I have a feeling that you have more than just misfire codes.
I would assume (we know where that goes) that the shop does have a proper scanner, but I do have an Autel that will be getting ordered soon that I've wanted for the Giulia (now that they can authenticate with FCA/Stellantis SGW) so can certainly run a proper scan.
 
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I would assume (we know where that goes) that the shop does have a proper scanner, but I do have an Autel that will be getting ordered soon that I've wanted for the Giulia (now that they can authenticate with FCA/Stellantis SGW) so can certainly run a proper scan.
Ugh, the SGW matter warrants their own thread, but it's a hassle. Not sure if you're aware, but it requires an active Autel software subscription at all times AND an active AutoAuth subscription ($50/yr?).
 

RamFan

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Ugh, the SGW matter warrants their own thread, but it's a hassle. Not sure if you're aware, but it requires an active Autel software subscription at all times AND an active AutoAuth subscription ($50/yr?).
Yeah tell me about it...

The Autel subscription is the part I'm trying to figure out. I don't mind paying the AutoAuth fee as needed - meaning if I only need it 3 out of 5 years then I'd just pay the fee the three times I need it and have coverage for a year. If you have info on the Autel portion feel free to DM though, they certainly don't make it very transparent.
 
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Hmm manual cleaning of the intake valves? That doesn’t sound like it’s going to have done a good enough job. Really they need walnut blasting or take the head off then valves out but that would be a lot of work/ expense.

Does it have a hesitation/ stumble with light throttle about 1800 - 2000 rpm? Will need to be driving to feel it not just reving the engine.
 
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RamFan

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Hmm manual cleaning of the intake valves? That doesn’t sound like it’s going to have done a good enough job. Really they need walnut blasting or take the head off then valves out but that would be a lot of work/ expense.

Does it have a hesitation/ stumble with light throttle about 1800 - 2000 rpm? Will need to be driving to feel it not just reving the engine.
I’m hoping to get my hands on it in the next week or so, playing the game of telephone can miss the finer details.
 

RamFan

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Finally was able to get a closer look at it and replaced the plugs as they're a cheap swap, and based on her service history it wouldn't have hurt. Rough start cleared right up and hasn't come back 2-weeks later.

My theory is that this was a carbon buildup issue from the beginning. The manual cleaning likely resulted in some broken carbon not being fully cleaned out, with a few additional cycles of the engine running, I think these deposits may have attached to the plugs causing the issue to return. I'm likely wrong, but that's the only sense I can make of it.
 
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