wont go over 40 mph & doesnt seem to shift od light on when od isnt on 1994 Volvo 940

also have heard some hissing noise as well, what is this caused by??? Thank you for your time

Asked by for the 1994 Volvo 940
It sounds like you have a few issues going on here.
1. Won't go over 40 mph. There are several possibilities, could be a failing fuel pump, mass airflow sensor or fuel pressure regulator, or something else. Need a proper diagnosis to determine what is causing this.
2. OD Light: Most likely the OD relay is failing, very common issue on the 940.
3. Hissing noise: noises need to be heard and an inspection performed to determine where it is coming from, otherwise it's a very wild peculation, and will always be wrong.
An experienced Volvo tech can figure these things out fairly easily, as these are fairly common complaints for this vehicle.
Hissing noise, any problems with the cat. on these models?
No, the catalytic converters didn't have many issues at all.
1 more answer
i have just had those same symptoms, i replaced my transmission filter first
actually i seen shavings on the filter but i replaced it anyway it helped but i had to replace the trans