I’m reaching out to the community for some guidance on my 1991 Mercedes 190e 2.6, automatic transmission, which has around 124,000 miles. It’s been a reliable car, and the only known issue was a minor valve guide seal problem. This hasn’t caused significant oil consumption, just a bit of carbon buildup on one spark plug that I usually clean when I change the oil. Spark plugs and the fuel filter were replaced recently, just a couple of thousand miles ago.
However, very recently, within just a few days and across only 20-30 miles of driving, the car has drastically changed from running perfectly to being almost undrivable. It started with a slight hesitation when accelerating. Quickly, it progressed to becoming hard to start, running very roughly, and then stalling when I put it into gear or if I press the accelerator pedal too quickly. The idle also seems higher than normal. Once I get past the initial hesitation and manage to build up the RPMs, the engine seems to rev relatively normally.
Thinking it might be fuel related, I drained the old gas and filled up with fresh fuel. I’ve visually checked for any obvious vacuum leaks, but I admit I’m not an expert in spotting them. The fuses are all good. I tried unplugging the Idle Control Valve (ICV). When I did this, the RPM dropped significantly, down to around 500-600rpm, and it barely ran at all. I’m taking this as a sign that the ICV is at least somewhat functional, and I cleaned it anyway just to be sure. There are no warning lights illuminated on the dashboard, so I don’t immediately suspect the Overload Protection Relay (OVP), though I did check and the OVP fuse is also fine.
At this point, I’m unsure what my next steps should be for troubleshooting. The heavy hesitation and stalling when accelerating strongly suggest a fuel delivery problem to me. However, the Bosch fuel injection system in the 1991 Mercedes 190E is more complex than anything I’ve worked on before.
I’ve spent a lot of time searching online forums and articles, but it’s been difficult to find threads with definitive solutions to similar issues on a 1991 Mercedes 190E.
Any advice on what to check next to get my 1991 Mercedes 190E running smoothly again would be greatly appreciated. Thank you for taking the time to read through this.
