Smelly exhaust

IS3FIFTY

IS3FIFTY

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My coupe's exhaust really smells bad. Bad to the point that I can't run the engine inside the garage and I feel for whoever drives behind me. No fumes or smoke, though. I believe that my Webers may be running rich as I recently changed the exhaust tip and the inside is already black. Could a too rich mixture be the cause for the bad smell? If not, what does this?
 
Did it smell good before?
Did you change something?
What does it smell like? Fuel or something else?
The new ethanol fuel is terrible and does not burn well.

Check to see that your chokes are are opening all the way.
 
i remember that smell from my high strung 2002. with its 45 dcoes, it ran really clean at revs ... but at idle ... really rich and a big idle lope. when georgia first started doing significant emissions checks i got one of the highest ever running tests ... HC was around 1700.

a year later, when the state changed to a dyno ... the car passed with flying colors because it wasn't being tested at idle.

the point is, cars that run extremely rich have a very smelly exhaust at idle. if you don't have a really high strung car that needs a lot of fuel at the top end, get them adjusted / re-jetted.
 
IS3FIFTY said:
My coupe's exhaust really smells bad. Bad to the point that I can't run the engine inside the garage and I feel for whoever drives behind me. No fumes or smoke, though. I believe that my Webers may be running rich as I recently changed the exhaust tip and the inside is already black. Could a too rich mixture be the cause for the bad smell? If not, what does this?
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You have a smelly exhaust but no fumes? Your description begets many questions.

A poor running engine can be caused by any number of reasons, excluding carburetion. What is your engine's overall mechanical condition? Is it tired with significant wear, so that carburetor adjustments and ignition "tweaks" are essentially work-arounds? Does the engine idle smoothly and pull smoothly though its normal rev range?

Are you certain the smell is from the exhaust? Dead animals or even certain live animals are capable of imparting an odor that most coupe owners might find offensive. Same with wet materials stowed in the trunk. Air conditioning condensation that collects usually on carpeting (usually in the cabin).

How long has the malodorous condition persisted? What work, other than the installation of an exhaust tip, was recently performed?

Any "special" fuel additives?

If, as you suspect, the smell is exhaust related and it involves unburnt fuel, there can be several causes other than the carburetors. If the problem is relatively recent and no one fiddled with the carburetors, then you can likely rule out improper jetting. BUT, there are many other things to consider that can cause a "rich" condition.

Is the crankcase properly vented so that the blowby from the top/side of the valve cover is ducted either to the engine intake (usually the air filter housing) or a catch can? If a catch can is used, is it full? Could there be too much blowby???

Are the air filters plugged with dirt - or clean? Are the choke plates fully open? Fuel filters generally work well but not forever and they are imperfect. Debris in the fuel can cause carburetors to poorly meter fuel. Late ignition timing can result in unburned fuel despite the best carburetor settings. I mentioned "special" fuel additives. I recall someone who inadvertently added diesel fuel to their non-diesel engine. The engine burned the fuel, and the aroma was vintage garbage truck.

Finally, are you one of the few that installed a catalytic converter in the exhaust? One well-known recipe for hydrogen sulfide (rotten egg smell) is to run an overly rich fuel mixture through a catalyst rendering it incapable of fully processing the mixture.



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Thanks everyone. Alright, here are some answers to all your questions:
- carbs are 38DGAS
- the car always smelled. I didn't change anything recently. I just can't stand it anymore :shock:
- smells like pollution... Impregnate my clothes and can smell it long after I take it for a ride.
- idle is very smooth when the car is hot, a bit rough when cold. Always starts well. Tends to Diesel if very hot
- chokes open up correctly
- no dead animals :smile:
- seems to smell more at idle than when revved
- no additives. Just premium 91 oct.
- engine is strong. Recent compression test shows consistent pressure across all cylinders.
- no catalytic converter
- PCV tube correctly routed to air filter assembly
 
A thought, Tightly wrap the tailpipe using a proper exhaust hose to the outside of the garage- be sure it is air tight so you can determine if the smell is coming out of the tailpipe or if you have a leak somewhere in the system before the tailpipe. Check ALL the fuel lines especially any return lines and the gasket on the fuel tank sender and filler neck. I have trouble distinguishing the smell of raw from burnt gas from the cabin as sometimes there is a combination of both in the cabin. Check your trunk gasket as well because even a clean running engine can kill you if the exhaust gas is getting sucked into the cabin. It's counter intuitive but there is sometimes lower pressure in the cabin when the windows are open, so the smell is actually worse with the windows open than when closed. Also any "holes" in the trunk that are not plugged can allow exhaust into the cabin. Another nasty little spot is where the gear shift enters the cabin, I used a VW CV boot to go around the shifter and seal the opening in the floor- good sound insulation as well. As Don said below, of course check that all ignition systems are working properly and you can look at the plugs to determine the mixture. Also, dieseling when hot is indicative of a possible over advance in timing which will lead to poor milage and of course a bad burning situation increasing exhaust smell. It seems that you'll have to go through a process of elimination that will take a while so please let us know what you find. Lots of us have "smelly" cars.:-(
 
When I see an older car in heavy Toronto traffic, I can usually smell the exhaust. If the cars currently on the road put out the emissions of the older days, lifespan in our city would be shorter.
 
IS3FIFTY said:
My coupe's exhaust really smells bad. Bad to the point that I can't run the engine inside the garage and I feel for whoever drives behind me. No fumes or smoke, though. I believe that my Webers may be running rich as I recently changed the exhaust tip and the inside is already black. Could a too rich mixture be the cause for the bad smell? If not, what does this?
Click to expand...

hummm, san diego makes the trip quite an expereience, just turn east, take it easy, it will be some hours, then when you reach a cliff and then water, find a harbour and get your coupe in a boat, tell them to sail east, and a bit up north, you will reach firm land, find a policeman and ask for directions, bilbao is the place, call me and we will hook the motortester to your beauty :D

bad smell ? incidentally some say nice smell, probably too strong, that means rich, mixture, ignition, many different causes,...
 
Exhaust smell in the cabin:
There is a seal between the engine compartment and the air inlet to the heater box, a bad seal will let air in the vent system. I think it is 51711810531
Engine smells can also come in around the shifter as Peter mentioned. There is a foam pad bellow the leather boot to help seal this. 23411200936
Raw fuel smell can come from the trunk.

With good seals you should not smell even a bad running car with leaky exhaust from inside.
 
I have a 69 Fairlane Cobra with a 428 CJ engine. When I bought the car, the exhaust would burn my eyes. I eventually put smaller jets in it and advanced the timing a little and that fixed the problem. It runs better now too.

I am guessing you need to take a look at the jets determine what is in the carbs and find out what is recommended for your car. I also run Webers (JAM Engineering kit) on my 2800CS but they were set up for my engine from the beginning. No foul odors except sometimes when cold and on the chokes.
 
Great suggestions everyone! I'll start with the mixture and the timing and will take it from there.

A few of you raised a good point about cabin insulation. I do occasionally smell gas vapors inside and around the car so will also check seals and gaskets all around.

@deQuincey: Thanks for the invitation. The last time I went to Bilbao was 16 years ago and would love to go back, especially if it involves meeting an E9 expert... ;-)

@gwittman: my Webers are also part of a JAM kit. It was installed a while ago, though. I guess time has come for tune up and synchronization.
 
gwittman said:
...I eventually put smaller jets in it and advanced the timing a little and that fixed the problem. It runs better now too.
Click to expand...

I have a '69 2800cs and it runs REALLY rich. Smells, black exhaust tip and I can get it to belch out a cloud if I gun it on the freeway. I'm running 38/38 Webers and put some jets in that Scott had (a local CS owner on the board). I'm convinced that its way over jetted and I'm going to buy some smaller ones and test them out.

The engine also runs over when turned off and my running temp is always a bit low. Once I get the jets I'll also play with the timing.
 
I had the exact same issue - several "mechanics" looked and found nothing. In the end it turned out to be 2 issues. The first was a series of small holes on in top of the exhaust ( they were not visible unless you remove the pipes and boxes). The second was the gas filler plastic expansion/breather bottle - the hoses were disconnected, (there are 2 hoses one to the neck of the filler the other to the roundel vent in the pillar). This drove me nuts for about a year until i got it figured out. Good luck.
 
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