Exhaust Fumes

[Ghoste]

Okay, I'm stumped.  I'm getting bad exhaust fumes in the interior at highway speeds.  Noticed as a sudden occurrence and not before, manifolds not headers, newer exhaust without corrosion, welded joints, no holes in exhaust, tips past valence, all body plugs in place, only happens with windows down.
Any ideas?

[flyinlow]

Hold your hand over each exhaust pipe and check for leaks. Both at the same time if you have a Xor H pipe.

Any recent interior changes?  New rust hole in floor? (Not to disrespect you car)

By a battery powered CO detector for your car until its fixed so you don't pass out. I keep one under the pass. seat.

[Ghoste]

No rust, thats whats driving me nuts about this.  Everything is clean under there, not concour's clean but it's no Michigan daily driver for the last forty years either, its clean.

[Windsor]

How is your trunk seal?  I've experienced the problem on a buddies car. While driving, there is enough of a low pressure area behind the car that it allows fumes to build up. If there is a gap between the seal and the lid, or any other gaps, the fumes can make their way into the passenger area.

[Ghoste]

It's good, almost as new. 

[green69rt]

Maybe coming in the vents    Have you looked at the seal between the hood and the cowl.  It's meant to keep engine bay fumes out of the cowl grill.  Maybe shut off the cowl vents and see if you still get the fumes.....

[Ghoste]

Tried that, it seems like its worse then but it could be overthinking since its hard to guage and I'm searching for it.  I did replace the heater core recently so one of the first things I checked was for a body plug accidentally kncocked out or anything like that.  Vent seal was in good condition and foam around heater hose inlet and outlet was okay.

[Charger-Bodie]

Have done anything to cause it to run richer lately ? Is the choke hanging up? Heat riser?

[Ghoste]

Hadn't considered that, good idea.  In the midst of tuning it now because it has started to run rough in lower rpm and surge around 1500 during cruise condition.

[Cooter]

Exhaust fumes, or just fuel vapors?? Remember, in Chrysler's infinate wisdom they ran the fuel vapor/overflow into the frame rail. 

[Ghoste]

No, definitely fumes.

[Cooter]

I know some body designes actually draw the air from the rear back into the cabin with windows down.

[Ghoste]

Yeah, thing here is that it didn't do it until all of a sudden.  This means something changed whether I did it or not and if its something I did, I surely should be able to find it and I can't.  Makes me want to scream.

[green69rt]

maybe another test...drive at highway speeds with the quarter windows down and the front up, then with the quarters up and the fronts down.  Maybe you can tell a diff .  Chasing a bad smell can be frustrating...

[ws23rt]

Just an out of the box idea. Are you using a different gas than before?  Or you could have developed a rich condition that might change the exhaust smell. Vents closed? or open?

One thing is for sure--since it came on suddenly it's likely to be one thing and those one things tend to be simple

[Dino]

My car developed a nasty exhaust smell in the cabin.  I checked all the exhaust joints but no leaks anywhere.  Recently I needed to remove my passenger side valve cover and found the gasket had torn and let oil run onto the header flange.  Not a ton, but enough to create a smell that came into the cab through one of many open holes in the firewall.  I replaced the gasket, cleaned the header and apart from a screw hole or two the firewall is closed up again.  Hopefully that'll do it.  Maybe your car has a similar issue?

[Back N Black]

What breather do you have on your valve covers? I have stock set up on my 69 440 and had a tear in the rubber hose to the air cleaner, bad smell in the car. New hose, smell gone.

[c00nhunterjoe]

What was the outcome? I had bad fumes in mine with the windows down. Windows up it was great. Resealed the trunk lid and it got better, sealed the entire trunk floor and it got better, removed the back seat and package tray and insulated it; 98% cured.