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2.3 In cabin Exhaust fumes


New Member
1987 Ford Mustang 2.3 runs rich and temperature won't move past 140 degrees. The electric fan turns on as soon as the car does and doesn't turn off. In cabin exhaust fumes get stronger on the highway. I have replaced the thermostat, water pump.


Active Member
Is the electric fan hooked up to a controller of any sort? A controller would trigger it on / off at what temp you want. It's going to struggle getting up to temp with the fan on all of the time.

And it sounds like you have an exhaust leak. Maybe on the exhaust manifold? The smell will definitely be more prevalent if it's running rich.

Sounds like it needs a bit of a tune to get past running rich.


Well-Known Member
Correct me if I'm wrong, but I believe the factory 2.3 cars had electric fans, didn't they? The two could be related. I don't believe the ecm would control the temp, so probably just a bad fan switch. Of course, the last time I owned a 4 cyl mustang was an 88 or 89 model around 1993, if I remember correctly. Do that math and that should age me pretty well lol!

Like Erkenbrand said, check for exhaust leak. The cool running temp will make it run rich, eventually ruining the cats and causing other issues with plugs, valves, etc. Check the temp externally with a ir gun or whatever. Make sure the gauge is showing correct temp. If it really is low, get the fan working properly and drive the snot out of it for a few days. I would suggest pulling a couple plugs before and again after. If they're black and sooty before, they should be cleaner after driving it for a while with warmer temps. That will let you know you're getting somewhere! It should have a bit more pep, as well!