I have been getting a lot of raw fuel fumes inside my car lately (1995 XJ6), especially when it's really cold outside. They are worse at idle and low speeds.

Also, the heater doesn't get as hot as I would prefer when it's near 0 degrees F. The temperature gauge seems to indicate the car is cooling ok.

 

I begin by a good inspection of the exhaust system. Any leaks?




Cooling OK, but does it get warm *enough*? Does the temp needle reach the "N"?
IF not, replace the thermo.

Next, make sure the heater pump is working. They often fail.

Both of the above are common issues.

That said, some complain of weak-ish heater performance even when everything is working properly. Selecting an artificially high temp setting is needed to produce the *really* warm air that you'd want in freezing weather.

Cheers
DD