Engine running problems

[Haithabu]

Hello everyone,

I have an intermittent issue that is occurring more and more frequently. Sometimes it happens right after starting, sometimes after a few minutes of driving, or even after a longer drive—the engine starts running unevenly (feels like it is running rich, and sometimes there is a smell of gasoline). Occasionally, the engine stalls. If it does not stall, it continues running in that state. Then I restart it (often while driving), and everything is fine again.

The idle stepper motor is new, and the behavior did not change after the replacement. The issue started gradually and has become more frequent—now it happens every other start or even during almost every trip. Otherwise, the engine runs very well.
Does anyone have an idea what I can test?

Cheers
Sven

P.S: This year, I have installed many new parts, including NOx sensors, air flow meter, fuel pump, fuel filter, and pressure regulator. None of it has made any difference to the issue....

[BritishTvr450]

There’s plenty of things you could be checking but your best to start with using Rovergauge to do some basic diagnostic checks.
Look up Rovergauge and invest in it as it can save a lot of faffing about.