Engine Dreaded exhaust/ fuel smell inside car


New Member
Oct 5, 2018
West Palm Beach, FL
I know this is one of the more common issues with these cars, but it’s driving me absolutely crazy lately. I rebuilt my 302 about 5 years ago, using the gt40p setup. The car runs flawless when I do drive it, which is maybe once a month. Within the last 6 months though there is a noticeable exhaust leak while the car is running, which is causing some really potent exhaust fumes. It also seems like the engine has started running very rich aswell. The fuel combined with exhaust smell is enough to choke you and burn your eyes. I can’t drive the car anywhere decent anymore because I show up smelling like gas and exhaust fumes. Now for the million dollar question, what are the common causes/ areas on the car that you guys have found cause this and where are the fumes coming into the cab from? I was going to put on an adjustable FPR, and install a new charcoal canister and lines from late model resto.. I may also go ahead and replace my header gaskets. Any info you guys have would be much appreciated. I’ve heard about 20 + issues that could cause this and I know it can be a process of elimination. Let me know, thanks!
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WAIT,you now have a pair?
10 Year Member
Apr 3, 2009
If it's any loose connections it will leave black soot marks, get a good couple of miles on her and put her on Jack stands front and rear,get under and search for tell tale signs.If you can't see anything then make sure she's cooled off and start her up , go under and feel for leaks.Good luck,let us know.Also it can get inside the car if shifter boot is cracked,or you have holes in floor board,old or missing firewall gromets.


Mustang Master
Aug 18, 2017
Are you still running the stock ecu with no type of tuning chip ?
Do you have an afr gauge to verify rich condition ?


You have a nice rear end there Dave.
15 Year Member
Nov 29, 1999
Mililani, Hawaii
Are you running an H or X pipe with no catalytic converters? If so, that is 90% of your smell. I have a younger friend who bought a coupe. It was super nice with a nice catted H-pipe. Of course he pulled that to put on the "racecar" off road H pipe with no cats after I repeatedly told him DO NOT DO IT. It wasn't but 2 weeks before he was crying about hating his car because he always smelled like exhaust.....and yeah, he got rid of the catted H pipe so he screwed himself.....


5 Year Member
Apr 16, 2015
One other thing to think of is are you running the stock clutch fan or e-fans?

The reason I ask is I just put e-fans on my 2004 F150. It has the typical exhaust manifold gasket leak and if running and standing still it will stink of exhaust in the truck - never had that before. The conclusion I have come to is the old clutch fan was always moving air around the engine and out engine bay. Now with e-fans, no air movement so stink just hangs around. Now I just manually flip low speed fan on and smell goes away.

If this is why, you still have an exhaust leak to deal with, but might explain the reason for some of the stink.
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