Rough idle/stalling at cold start up goes away after reaching temperature?

MMAYFIELD711

MEMBER
2014 VOLKSWAGEN PASSAT
1.8L
4 CYL
2WD
AUTOMATIC
132,890 MILES

When first starting the car for the day, as it starts to warm up the car's RPMs will jump, and the car will stall. The rough idle only happens between 1 and 2 RPMs, if I accelerate past 2 RPMs, there is no problem. Once the car is warmed up, there is no problem with rough idle or acceleration.
Also, when I fill up the gas tank, the car will idle rough and throw misfire codes.
I changed the spark plugs; this solved the problem for about 2 weeks.
2 days ago, I woke up to a dead battery that was only 2 years old and the rough idle at start up is happening again.

I was told that it was a timing system issue and I should just get a new car without any real details.
I am thinking it could be an alternator issue. There is some occasional whining coming from the engine bay, no ticking or grinding.

Any help would be appreciated!

3 Replies

JACOBANDNICKOLAS

MECHANIC
109,755 POSTS

Hi,

Since it runs normally once operating temperature is reached, chances are it has nothing to do with timing. My guess is a coolant temperature sensor or an engine vacuum/evap issue.

It could deal with the engine coolant temperature sensor. This sensor is used by the PCM to determine how rich or lean the fuel mixture needs to be based on temperature.

If you have a live data scan tool, before starting the engine (cold) check to see what signal is being sent by the sensor.

On the other hand, since you also experience an issue after refueling, there could be an issue related to the EVAP system. By any chance, have you ever retrieved any codes other than a misfire code?

Here is a link that explains how to locate and repair an engine vacuum leak:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Let me know.

Joe

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Saturday, October 5th, 2024 AT 8:31 PM

MMAYFIELD711

MEMBER
2 POSTS

Hi Joe,

Radiator and coolant temperature sensor are less than 2 years old.
I've had to replace the radiator twice due to bad parts so maybe that could be it.
I don't have a data scan tool unfortunately.
I'll be taking it to another mechanic soon, I'll ask him to check both the coolant temperature sensor and evap system.

Here are the codes from the shop's diagnostics:
P0341: camshaft position sensor A
P0011: camshaft position timing over-advanced
P0300-P0304 for the misfires

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Sunday, October 6th, 2024 AT 5:47 AM

JACOBANDNICKOLAS

MECHANIC
109,755 POSTS

Hi,

The codes you provided are related to intake valve timing. If I was to start testing, I would focus on the P0011 first.

Take a look through the directions below and let me know if you are comfortable performing the diagnostics.

Let me know

Joe

See pics below.

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