Idle air control valve problem or vacuum leak

[esandes]

This only happens when it's cold outside. Fall/winter/spring but worst during the winter. The colder the engine, the worst it gets.

The engine almost stalls out when coming to a stop while the engine is still cold. It goes away after the 1st or 2nd near stall.

When the engine is warm, it never happens no matter how cold the ambient temperature is.

The shop monkeys never know anything because this doesn't trip a code.

Discuss.

[esandes]

I found a plausible explanation in another forum that the excess moisture in the PCV during the very cold startup causes the mechanism in the PCV to not work properly.

[esandes]

Bad EGR valve?

[Brillo]

I found a plausible explanation in another forum that the excess moisture in the PCV during the very cold startup causes the mechanism in the PCV to not work properly.

I have no clue what your driving habbits are but shorter trips may gum up the PCV valve. So I suggest that you eiher replace it or thoroughly clean it with brake cleaner. Reinstall and see if it works better on your cold engine stops. If that works, it might be worth replacing with one that is less temperamental, and also keep your car in a heated garage, or don't stop until the engine is warmed up.

[gyroscope]

check the diaphragm on the PCV valve.

[esandes]

Thanks!

[canadianA4B7]

See if you can also cycle the run flaps with vcds. They may not be fully opening. I’ve seen this before.

[Jay-Bee]

Point me to an Idle air control or Exhaust gas recirculation valve on a 2.0T

lmao

[esandes]

See if you can also cycle the run flaps with vcds. They may not be fully opening. I’ve seen this before.

I had them removed for apr 2+.

I'm getting a new PCV installed in a few days. I should also switch to stock heat range plugs. I currently have 1 step cooler plugs. If none of this works..new coilpacks.

[EvolutionArmory]

I had them removed for apr 2+.

I'm getting a new PCV installed in a few days. I should also switch to stock heat range plugs. I currently have 1 step cooler plugs. If none of this works..new coilpacks.

You know those things you removed? Their whole purpose is to make your car not have this problem on cold starts 🤣

You paid good money to make your car run worse. The runner flap delete is probably the most usesless mod out there next to PCV block off plates.

At least it only took 9 posts for you to tell us the flaps are deleted.

Just throw some coilpacks in it 🤣🤣🤣

[esandes]

Ok if you think so. I have had 2+ for about 8 years. It has happened only last year and this year only in the colder days. Like -10C or colder.

Anyone with simple sense would come to the conclusion that a part is worn out.

I will let you all know how the PCV swap goes.

[EvolutionArmory]

Is your car an automatic? Do a torque converter stall speed test if it is. You can google how to do it.

[EvolutionArmory]

And let’s look at “simple sense” things that make your car stall when it’s cold.

Carbon build up on the injectors. You have made it known that you’ve had the car for 12 years and haven’t had a carbon cleaning done.

Intake runner flap problems. You’ve had the flaps deleted so right off the bat you’re at a disadvantage because the tumble flaps are there to assist in cold starts and low RPM and idle situations.

Your throttle body is the main component that controls idle speed

A possible torque converter situation if you have an auto.

Since your issue only happens for a few minutes before the car reaches operating temp, those are the components I would look at first.

[esandes]

Is your car an automatic? Do a torque converter stall speed test if it is. You can google how to do it.

Yes..auto. I had two partial flushes of the transmission fluid and the transmission fluid filter was also changed. This cold stall at stops started after the 2nd flush too. Perhaps the fluid is too thick when cold?

[Jayz691]

Yes..auto. I had two partial flushes of the transmission fluid and the transmission fluid filter was also changed. This cold stall at stops started after the 2nd flush too. Perhaps the fluid is too thick when cold?

Did you use the correct fluid? Depends on software of trans. If its updated past like 0030 or something, you need lifeguard 8. If it's lower, like 0010(not sure of exact numbers), then lifguard 6. Wouldn't use cheap fluid, just ZF lifeguard, cuz these transmissions are finicky to the fluid used.

Sent from my VS995 using Audizine mobile app

[esandes]

And let’s look at “simple sense” things that make your car stall when it’s cold.

Carbon build up on the injectors. You have made it known that you’ve had the car for 12 years and haven’t had a carbon cleaning done.

Intake runner flap problems. You’ve had the flaps deleted so right off the bat you’re at a disadvantage because the tumble flaps are there to assist in cold starts and low RPM and idle situations.

Your throttle body is the main component that controls idle speed

A possible torque converter situation if you have an auto.

Since your issue only happens for a few minutes before the car reaches operating temp, those are the components I would look at first.

Regarding carbon cleaning. I just had a new clean head installed over the summer. No change in cold weather stalls compared to the old head. Maybe I should have installed new injectors but why would fouled injectors cause issues only when it's cold?

I cleaned the TB a few months ago. Same with the MAF meter.

Like I mentioned, the runner flaps have been deleted for a few years. The problem started last winter.

This is a temperature related issue. When it's cold the ATF is very thick. It wasn't OEM fluid that was used when I had the two tranny services. It could be the TC. If it is I will have to let the engine warm up at cold starts to prevent the near stalls when stopping.

Coolant temperature sensor?

[EvolutionArmory]

Diagnosis is a process of elimination based off of what you tell us.

With a new head, that rules out carbon on the valves. That’s what I meant to type and didn’t notice I wrote injectors until you just pointed it out. Sorry about that man.

Cleaning the MAF and TB is good but to really check them you would use VCDS. You would check MAF values at idle, which should be 2.5 or so. Then you would do a full throttle pull. It should be about 160 at redline. If the numbers are really off, your MAF is bad.

To check the TB you would look at the value at idle. The 2 numbers should equal 100% when added up at idle and as you move the pedal, they change but should always equal 100% when added together. If it’s off, your throttle body is bad.

This sounds like a transmission problem honestly. Sounds like a torque converter. You could have used the wrong fluid and maybe that’s not helping.

I can’t stress enough that running OEM fluid by VIN is always a good idea.

[esandes]

It hasn't been too cold since the PCV was replaced but the engine runs way better. It seems to make more boost.

But I did also replace the plugs with ngk ruthenium plugs. It's the model that is specifically designed for boosted engines. Finally a plug maker who gets it.

[EvolutionArmory]

Yup, changing your spark plugs fixed your car again.

I thought you said Denzo plugs were the best? 🤣

[Jay-Bee]

But I did also replace the plugs with ngk ruthenium plugs. It's the model that is specifically designed for boosted engines. Finally a plug maker who gets it.

Dude i really don't mean to keep coming back to your posts but you are eating up everything sold to you like it's the milk out of god's titties.

I had a 2 hour web meeting from NGK about those plugs, they were not designed specifically for boosted engine they have 2 different tip configurations and it's a harder element than Iridium... longer life that's it. The ground electrode is still platinum. They claim "High ignitability" and show some cool visuals to pull you in.

How are you making the assumption that your ATF is "thick" when cold? Most Low viscosity ATF fluids pour the same hot or cold they have so many modifiers in them.

[EvolutionArmory]

With all these advances in plug technology, it’s funny that simple 2 dollar copper plugs have better spark 🤣

They just don’t last very long.
Dude, I’ve run almost every NGK plug in the 7 range, Bosch plug in a 5 range and even ran a NGK 8 heat range.

Neither plug did anything different than the OEM PRF7S8EG plugs that I could feel in the drivers seat or measure through VCDS.

If your plugs are the right heat range, are gapped right, torqued down right and aren’t a junk brand, they will perform about the same. Plug debates are as useless as oil debates.

[esandes]

Did you use the correct fluid? Depends on software of trans. If its updated past like 0030 or something, you need lifeguard 8. If it's lower, like 0010(not sure of exact numbers), then lifguard 6. Wouldn't use cheap fluid, just ZF lifeguard, cuz these transmissions are finicky to the fluid used.

Sent from my VS995 using Audizine mobile app

You're 100% correct. This is the root cause. The garage didn't use OEM ATF.

Thanks!

[esandes]

Dude i really don't mean to keep coming back to your posts but you are eating up everything sold to you like it's the milk out of god's titties.

I had a 2 hour web meeting from NGK about those plugs, they were not designed specifically for boosted engine they have 2 different tip configurations and it's a harder element than Iridium... longer life that's it. The ground electrode is still platinum. They claim "High ignitability" and show some cool visuals to pull you in.

How are you making the assumption that your ATF is "thick" when cold? Most Low viscosity ATF fluids pour the same hot or cold they have so many modifiers in them.

I recommend that you bolt on some serious mods done then talk about your experiences with parts. 20 psi boost on 100 octane does a number on stock heat range plugs and plug gap.

Lower temperatures, higher viscosity is what I meant about the ATF.

[esandes]

https://www.counterman.com/ngk-intro...nical-sensors/

[esandes]

With all these advances in plug technology, it’s funny that simple 2 dollar copper plugs have better spark 🤣

They just don’t last very long.
Dude, I’ve run almost every NGK plug in the 7 range, Bosch plug in a 5 range and even ran a NGK 8 heat range.

Neither plug did anything different than the OEM PRF7S8EG plugs that I could feel in the drivers seat or measure through VCDS.

If your plugs are the right heat range, are gapped right, torqued down right and aren’t a junk brand, they will perform about the same. Plug debates are as useless as oil debates.

Exactly. They don't last long. You are running serious mods too and for me, the plugs just get fried or they're a bit too cool (one step cool) and misfire when the engine is cold.

[Jay-Bee]

I recommend that you bolt on some serious mods done then talk about your experiences with parts. 20 psi boost on 100 octane does a number on stock heat range plugs and plug gap.

Lower temperatures, higher viscosity is what I meant about the ATF.

Serious mods equal serious bidness bro. I'll make sure to throw race gas in my car and run the k03 turbo past it's efficiency range... will report back!

[EvolutionArmory]

I run 26 PSI spikes and hold 20 PSI to 6K on stock PFR7S8EG plugs gapped to .028. Running a 8 heat range and smaller gap didn’t do anything for me as far as timing correction factor goes on a timing log. I’ll get 40k out of them and I’ll replace them.

They’re just spark plugs. Run the plug the MFG or your tuner recommends. For me, GIAC recommends the stock plugs and they work great.

[esandes]

Serious mods equal serious bidness bro. I'll make sure to throw race gas in my car and run the k03 turbo past it's efficiency range... will report back!

Welcome to my ignore list

[AMCast]

Hey everyone. Just wondering if this issue was ever resolved. I am having the same exact problem. I have a '12 a4 b8 2.0t running apr stage 2+. My problem is a rough idle for the first few minutes on cold start. And worse on cold days. I've done intake valve cleaning, changing spark plugs. The difference is that I am getting a CEL. Intake air leak, multiple cylinder misfires and mixture too lean. Another symptom I'm having is the smell of gas in the garage. I'm replacing the low pressure fuel pump today. Also, I'm waiting for an oil catch can and changing out the PCV on it. Car has 88k miles.

[AMCast]

Ah crap just realized this is b7 platform forum. Sorry. But still I'd like to know what solution to worked.