Shudder When Idle, Volvo 850 96 Sedan

[reptar]

Hi Volvo enthusiasts. Wondering if I can pick your brains on a particular issue I'm having with my Volvo 850 96 10V NA Sedan.

It seems to intermittently shutter once or twice every 30 seconds when idle and after engine has been driving for 20+ minutes. Also, when accelerating gently from idle, there is also a slight hiccup (also intermittently). If I put the gear into neutral (instead of D) when idle, there is no shutter - almost as if removing the load is helping the situation.

The other day, I had been driving for 15 or so minutes. I was idle, to give way to another car. When the other driver hesitated to give way to me instead I quickly accelerated to eliminate the confusion. The quick acceleration from idle caused a sudden series of strong hiccups then power returned to allow me to drive. For the rest of that trip, whenever idle, the car would constantly shutter at idle - more than usual. I pulled off to the side of the road, turn the car off, then restarted. The shutters disappeared for the remainder of the 10 minute journey.

Is there a series of checks I can do to troubleshoot? Common parts that may be the culprit?

Thanks for your time.

[scot850]

Start with the fuel pressure. Should be in the 43 psi range.

Neil.

[reptar]

The fuel pressure when the ignition is turned onto Accessories (without engine firing) is 40 psi. When I start the engine and it sits in idle, the fuel pressure is 35 psi. Is this a pass?

The stutter only seems to happen when the car has been running for 20-30 + mins and sometimes it doesn't happen at all.

I have a new distributor and rotor lying around. Should I replace the existing one for the next check?


Engine Off, Accessories Mode
https://ibb.co/cXjYF2Q

Engine Idle
https://ibb.co/KF7hV6X