Need help.. 2001 Volvo s80 2.4 n/a

Morris56 · Post by **Morris56** » 16 Jul 2026, 14:09

Car Model: 2001 Volvo S80 2.4L (Naturally Aspirated / Non-Turbo, 5-Cylinder)

The Symptom:The engine runs fine most of the time. However, when the car is stationary at idle, and I rev the engine up to around 2000 RPM, hold it there for a few seconds, and then release the throttle back down to idle, the engine will sometimes begin to stumble heavily and misfire.
When this happens, it drops down to running on only 3 or 4 cylinders and triggers a misfire code specifically for Cylinder 1.
What has already been checked and ruled out:Compression: Tested and confirmed good compression across the cylinders.
Spark Plugs: Brand new spark plugs installed.
Ignition Coils: Tested by swapping them around, and even installed one brand new coil.
The misfire code stays locked on Cylinder 1.Fuel Injectors: Brand new fuel injectors installed.
Swapping them does not move the code.
Wiring: The wiring harness to the ignition coils and injectors has been inspected and confirmed to be in good condition.

I dont know where to go from here, so if anybody can help me it would be nice

Morris56 · Post by **Morris56** » 19 Jul 2026, 13:35

Nobidy?

Post by **volvolugnut** » 19 Jul 2026, 15:12

Are the spark plugs OEM and gapped to factory specs?
Is throttle plate clean? Is the electronic throttle original or has it been replaced?
Mileage and general state of service?
volvolugnut

Post by **RickHaleParker** » 21 Jul 2026, 14:40

Dirty Throttle Body and Vacuum Leaks are the two most common causes of stumbles and misfires after going from high idle to low idle.

Vova585 · Post by **Vova585** » 21 Jul 2026, 20:53

Agreed woth volvolugnut and Rick.
I would add that clogged PCV system is frequently can cause lots of issues with misfire codes. It would be great to start with a "glove test". Next move to smoke test the intake(it is non turbo so way easier). If above all check great, I would move to intake vacuum drop test or exhaust restrictions test through upstream O2 hole. Restricted catalytic or exhaust can disrupts fresh air delivery and causing combustion issues.
If above also checks great, well, connect fuel pressure gauge and see what this car is doing . Is it able to hold steady pressure or is it to low(quite a slim chance in your case based on symptoms, but we are pulling in a straws at this time).
Ok, imagine pressure is great as well...
Get a scanner and look at fuel trims(can always start here if you have a decent scanner able to read trims). What is the long trim for this car? What is the short trim upon idle?
As volvolugnut mentioned, OE/OEM parts where possible and able to afford.
Good luck