Stumbling S4

[s4sprint]

Anyone else have these symptoms: During the first 1-2 minutes after a cold start the engine stumbles or hesitates during light acceleration? It was first noticed during the winter but seems to be getting more noticeable, even as the weather has warmed. I never noticed it before this winter. After two minutes the stumbling disappears and runs perfectly. The car is 2011 with 40k miles.

[JD S4]

Anyone else have these symptoms: During the first 1-2 minutes after a cold start the engine stumbles or hesitates during light acceleration? It was first noticed during the winter but seems to be getting more noticeable, even as the weather has warmed. I never noticed it before this winter. After two minutes the stumbling disappears and runs perfectly. The car is 2011 with 40k miles.

Could need new plugs or could have leaky super charger intercoolers dripping coolant into the cylinders.

[4RCFED]

Could need new plugs or could have leaky super charger intercoolers dripping coolant into the cylinders.

^ What he said, check your plugs.

[pdqgp]

Anyone else have these symptoms: During the first 1-2 minutes after a cold start the engine stumbles or hesitates during light acceleration? It was first noticed during the winter but seems to be getting more noticeable, even as the weather has warmed. I never noticed it before this winter. After two minutes the stumbling disappears and runs perfectly. The car is 2011 with 40k miles.

My guess is one of the heat exchangers on the sides of the supercharger has a slight leak/crack. It's then dripping coolant down onto one of the cylinders and fouling out the plug. Once it burns off it runs fine. As it worsens it will likely throw a code.

[MSq5]

Anyone else have these symptoms: During the first 1-2 minutes after a cold start the engine stumbles or hesitates during light acceleration? It was first noticed during the winter but seems to be getting more noticeable, even as the weather has warmed. I never noticed it before this winter. After two minutes the stumbling disappears and runs perfectly. The car is 2011 with 40k miles.

Do you have VCDS? Data logging might help find the problem.

One thing - worse scenario would be a cracked cylinder head. This can happen if you get in subfreezing weather and don't have enough antifreeze. The frozen water/coolant expands as it freezes and causes a small crack in the cylinder head above the water jacket.

What happens then is that when you start the engine water leaks through the open crackinto the cylinder causing a misfire. But, as the cylinder heats up, the heat expands the metal and the crack closes, sealing back up. Blown headgasket can do the same thing sometimes. If you haven't overheated, its probably just the s/c jacket leaking.

I hope its just the s/c water jacket. Easier, less expensive fix. Either way, you would be losing coolant and having to top off. Is that happening?

[Ford Prefect]

Anyone else have these symptoms: During the first 1-2 minutes after a cold start the engine stumbles or hesitates during light acceleration? It was first noticed during the winter but seems to be getting more noticeable, even as the weather has warmed. I never noticed it before this winter. After two minutes the stumbling disappears and runs perfectly. The car is 2011 with 40k miles.

Same car and mine does this too, although I have 70k more miles and just recently changed the plugs, but I’ll check them nonetheless.

I’m EPL stage 2 also. I’ll flash back and see if mine clears, I thought it was the tune and the EPC light some of us were getting in the extreme cold.


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[s4sprint]

I am not losing coolant. I also have the original plugs installed. Audi says to change them at 55000 miles. What mileage are guys beginning to see issues with their plugs? I bet most people change their plugs prior to having any issues. My guess is that I do not have a coolant leak because there are no misfires on startup and the car will idle perfectly. The only issue is with light to mild acceleration within the first two minutes in first gear (manual trans), while still within cold start parameters. Ford Perfect - did the plug change eliminate the stumbling?

[pdqgp]

I am not losing coolant. I also have the original plugs installed.

Check the plugs. See if any are fouled. If one is fouled more than others borrow a scope and get a look-see down there? Easy to pop one in there to see as you'll clearly see a clean spot on the cylinder if coolant is dripping. Could just be a small amount that you may not notice right away. Any codes thrown? Could be a coil on it's way out.

[EIAlfonso]

If you’re going to check the plugs you might as well change them, and it’s 55k or 6 years, you’re due anyway


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[Ford Prefect]

I am not losing coolant. I also have the original plugs installed. Audi says to change them at 55000 miles. What mileage are guys beginning to see issues with their plugs? I bet most people change their plugs prior to having any issues. My guess is that I do not have a coolant leak because there are no misfires on startup and the car will idle perfectly. The only issue is with light to mild acceleration within the first two minutes in first gear (manual trans), while still within cold start parameters. Ford Perfect - did the plug change eliminate the stumbling?

I had no stumbling for after my plug change last year. It seems relatively new after this winter. I’m not losing coolant either. I need to flash to stock and drive it for a few days, I’m really curious if it’s the same.


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