Engine: B5204: COLD start misfire diagnosis help

[Verracciii]

Hey everyone, I need some help diagnosing an issue with my car.

I have a 2001 Volvo S60, and recently it's developed a rough misfire when starting cold. Here's the situation:

- Cold Start Misfire: When I start the car cold, the engine misfires and the revs jump up and down.
- Driving Conditions: I drive to work on a dirt road where I have to go really slow, about 1,000 RPM in first gear for 10 minutes. I notice the misfire after this drive when I leave work.
- PCV Valve: I recently changed the PCV valve.
- Spark Plugs: The spark plugs are about 4 months old.
- Overheating Incident: About a month or two ago, the engine overheated. The issue causing the overheating has been fixed, but I'm worried it might have caused a gasket leak.
- Performance Details: The misfire goes away if I press the gas a little or if the engine is warm.
- Idle Issues: The engine has idled rough when cold since the overheating incident, however, this specific misfire is typically after the drive to work.
- No Contamination: There's no oil or coolant contamination.
- White Smoke: Occasionally, there's a bit of white smoke, which was happening even before the overheating incident. Yet, my coolant or oil has not decreased for a while.

I'm thinking the head gasket might be leaking between the cylinders. The misfire issue started after my first shift at work where I have to drive slowly on that dirt road.

Here's an example of the problem but on a BMW, mine is slightly worse: Link

Any thoughts or suggestions on what might be causing this? Thanks!

[Georgeandkira]

You failed to mention:
Which engine?
How many miles on the vehicle/engine?

Easy questions / less expensive suggestions first:
Any codes?
Did you install correct plugs?
The PCV system in any vehicle is a source of vacuum leaks. Did you install it correctly?
Have you cleaned the MAF sensor?
Might the Coolant Temperature Sensor be bad? Mine went on my 2002.
Try dosing your gas with a good injector cleaner like Chevron Techron. You want a cleaner with PEA in it. Do this before a stint of local driving.
Have you ever changed the fuel filter?

A bit more involved:
Get a compression gauge and perform a simple compression check.
A leak between two cylinders will appear as two identical readings in adjacent cylinders. This isn't at all complicated to do.

Since you remove the spark plugs for a compression check, carefully inspect for evidence of arcing coils. Burnt marks and sometimes smell tips them off. However, a miss will usually have an accompanying code. These are your P0300 through P0305 codes; with P0300 being "random" and P0301-P0305 being cylinder specific.

[Verracciii]

Originally Posted by Georgeandkira

You failed to mention:
Which engine?
How many miles on the vehicle/engine?

Easy questions / less expensive suggestions first:
Any codes?
Did you install correct plugs?
The PCV system in any vehicle is a source of vacuum leaks. Did you install it correctly?
Have you cleaned the MAF sensor?
Might the Coolant Temperature Sensor be bad? Mine went on my 2002.
Try dosing your gas with a good injector cleaner like Chevron Techron. You want a cleaner with PEA in it. Do this before a stint of local driving.
Have you ever changed the fuel filter?

A bit more involved:
Get a compression gauge and perform a simple compression check.
A leak between two cylinders will appear as two identical readings in adjacent cylinders. This isn't at all complicated to do.

Since you remove the spark plugs for a compression check, carefully inspect for evidence of arcing coils. Burnt marks and sometimes smell tips them off. However, a miss will usually have an accompanying code. These are your P0300 through P0305 codes; with P0300 being "random" and P0301-P0305 being cylinder specific.

B5204T5
Around 120k miles

I will need to check the codes, no check engine light though.
Plugs should be correct ones, furthermore no issues arose from them until this month (installed 4 months ago).
I will need to check PCV as you mention.
I have not cleaned MAF. Whats the best way to do this?
Possibility, where would it be located?
Bought the car at around 90k miles, since then fuel filter not changed, unsure about previous owner.

I will try to read codes very soon, would misfire codes throw up a check engine? Also, what would I be able to conclude from the burnt, smelly spark plugs?

[Georgeandkira]

The Coolant Temperature Sensor is aside the thermostat and separately replaceable. In later models, the stat and sensor is housed in a single unit.
Many would replace the stat along with the sensor. I just changed my sensor.

Any scorching and bad smell is the coil failing, not the plugs.

The MAF sensor is in the engine intake air handling tubing after the air cleaner. Some are wrapped in a metal box while others are delicate, framed wire assemblies out in the airflow. Spray them with MAF Sensor cleaner. Many electric cleaners leave a coating you do not want.