Rotten Smell After Hard Acceleration

[JoeSpeed]

Time to go Catless

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[Cory S]

Is the car up to full operating temperature when this happens????

How is this smell getting into your cabin during WOT?

 

[Cobra Jet]

One way of knowing if a catalytic converter is clogged - if you look under the car and it's glowing red, it's bad. This can be easily seen at night, but also during the day if the car was being flogged.

The midpipe system on the S550 is easy enough to remove to inspect the cats... remove and use a high powered LED flashlight to view the honeycombs for damages (ie: melting, disintegrated, broke or cracked sections, etc)...

Just an FYI -
The factory emissions is covered by an 8yr/80k warranty - whichever comes first.

 

[NoahsArk117]

Anybody else in the car with you, maybe unaccustomed to the Mustang’s hard acceleration?

Is the car up to full operating temperature when this happens????

How is this smell getting into your cabin during WOT?

Yeah I always let the car reach 180 head temp before doing any hard pulls. I'm not sure either, just started a few days ago. Haven't noticed a change in performance, idle condition, no check engine light. Not sure how it's happening.

 

[NoahsArk117]

One way of knowing if a catalytic converter is clogged - if you look under the car and it's glowing red, it's bad. This can be easily seen at night, but also during the day if the car was being flogged.

The midpipe system on the S550 is easy enough to remove to inspect the cats... remove and use a high powered LED flashlight to view the honeycombs for damages (ie: melting, disintegrated, broke or cracked sections, etc)...

Just an FYI -
The factory emissions is covered by an 8yr/80k warranty - whichever comes first.

Yeah im going to take it on a quick drive and see how it looks. Also going to setup something with Ford to look at. Pretty sure they'll fight me on the warranty since I have a catback but it's worth a shot.

 

[NoahsArk117]

One way of knowing if a catalytic converter is clogged - if you look under the car and it's glowing red, it's bad. This can be easily seen at night, but also during the day if the car was being flogged.

The midpipe system on the S550 is easy enough to remove to inspect the cats... remove and use a high powered LED flashlight to view the honeycombs for damages (ie: melting, disintegrated, broke or cracked sections, etc)...

Just an FYI -
The factory emissions is covered by an 8yr/80k warranty - whichever comes first.

So a little bit of an update here. I took the car out just a moment ago and really wrung it out for about 15 min or so to make sure it got nice and warm. I brought it back to my house and set it in the garage to look at the cats. Both cats look fine and aren't glowing red, I went ahead and gave both of them a few whacks with a rubber mallet to see if I heard anything and they sound fine. I will say that I've owned this car for about 2 years now and have never smelled anything like this before. This issue started about 5 days ago and I've fueled up twice since then. Both times I bought fuel was at this newer gas station by my house that I usually don't go to. Im starting to think that this could be caused by some bad gas. I'm going on a road trip today and will try a different gas station to see if anything changes.

 

[Cobra Jet]

So a little bit of an update here. I took the car out just a moment ago and really wrung it out for about 15 min or so to make sure it got nice and warm. I brought it back to my house and set it in the garage to look at the cats. Both cats look fine and aren't glowing red, I went ahead and gave both of them a few whacks with a rubber mallet to see if I heard anything and they sound fine. I will say that I've owned this car for about 2 years now and have never smelled anything like this before. This issue started about 5 days ago and I've fueled up twice since then. Both times I bought fuel was at this newer gas station by my house that I usually don't go to. Im starting to think that this could be caused by some bad gas. I'm going on a road trip today and will try a different gas station to see if anything changes.

Good research and diagnosis so far.

When you get it down to at least 1/4 tank, go fill at another station and see if that does make any difference in the exhaust smell.

You're not using or adding any additives to the fuel, correct? I think we've also seen threads on here from folks who add octane booster, it can also change the inside color of the tailpipes.

And believe it or not - there used to be additives that can be added to make exhausts smell ...fruity... don't know if that is still a thing... LOL!

 

[TopJimmyCooks]

Hey guys,

A few days ago I noticed a rotten suffer like smell whenever I would floor it. Goes away pretty quickly after and isn't present during normal driving. Is this something to be concerned with?

That's the smell of the tormented, damaged, souls whose spirit you just crushed with your hole-shot.

 

[Qcman17]

No. It's coming from the catalytic converter. It's normal

This …. mine does it when I ring the shit out of it. It’s a sulphur type smell and it doesn’t matter what fuel I put in it. Been like that since new and I know others here have noticed it too.
It’s normal and not worth worrying about or getting checked out.

 

[Balr14]

If I hit the gas hard on my GT my wife would crap her pants. Maybe something like that is happening...

 

[sk47]

Hello; The cat converter is a stove designed to burn excess fuel that is not fully burned during engine combustion. With a lot of excess fuel to burn they can get very hot.

A key is that you smell the bad odor after hard running. The programming for the injectors may be doing a normal thing and running a bit rich. Sager for the engine to be a little fat (rich) during hard runs. So, this may be normal to a degree. I too have smelled other cars on hills pulling hard.

The other key is that you only started smelling this of late. No clear idea on how important that may be. Could be the sort of thing that had been happening before and you did not notice. Now that you have noticed it could be you are sensitive.
A thing to do is do some mild driving for enough miles to get plenty warmed up but no hard pulls. Then park and let it idle while you walk around the car. This will not be conclusive but if the smell is at all strong after some mild driving would be something to check further.

Had a friend who ignored his cats for a long time and damaged an engine. Our best guess is the O2 sensors went out of spec and the engine was running rich. He partially melted the guts of the converter (stove got too hot) and had a lot of backpressure and heat build up. Seems the exhaust valves warped from the trapped heat. It also had bad fuel mileage. But hey, it ran for a long time that way. Now he replaces the O2 sensors on a regular basis.

Odds are you are not in a serious condition if it is only after a hard run. But also something I would check out myself. Good luck

 

[Spodie5.0]

I have a 2021 and have the same issue. Almost like a gun powder smell and only does it after a hard pull and then goes away. Everything seems fine with the car though.

 

[SBPGT]

I also have the gun powder smell, sometimes it smells like burning hair or someone getting a perm. I have a V6 with a tune and when I get on it the A/F drops to mid/low 11's. So it might just be the extra fuel and/or their ethanol blend or additives in it? Maybe the cats are losing their ability to convert all the gases during WOT pulls?

 

[sk47]

I also have the gun powder smell, sometimes it smells like burning hair or someone getting a perm. I have a V6 with a tune and when I get on it the A/F drops to mid/low 11's. So it might just be the extra fuel and/or their ethanol blend or additives in it? Maybe the cats are losing their ability to convert all the gases during WOT pulls?

Hello; My take on how the cats work is they get hot enough to cause a more complete combustion of the volatiles (excess fuel and oil) that escape the engine. If these fuels/oils burn at too low a temperature some bad compounds are formed. Burned at higher temps the excess fuels wind up as compounds considered to be less polluting. So, the more of that rotten egg smell should mean the cats are doing their job.

I think you are correct in that the air fuel ratio (A/F) gets richer at WOT. Running too lean at WOT is a way to kill an engine. So, the working idea seems to be the programing of the injectors fattens up the A/F at WOT or other such heavy working loads of an engine. An occasional rich condition is not a problem and is part of the plan. It is when the fuel mix is too rich too often that the cats can get hot enough to start to melt their guts.

I tend to think the OP is good except that the smell seems to have appeared recently and has shown up often since being first noticed. On a vehicle with high mileage I would suspect the O2 sensors have begun to fail. On a low mileage engine that does not seem likely unless some chemical which damages the O2 sensors has gotten into the fuel system or perhaps the computer parameters (tune) is altered somehow. Just guesses on my part.

 

[NoahsArk117]

*Final Update*

I was driving to my local mechanic yesterday and when I pressed the clutch in to go from 2nd to 3rd the car shuttered hard. After that the clutch engagement point was maybe 1/8" off the floor instead of the 1.5"-2" up that it normally is. When I got to the shop we looked at the exhaust and the new found clutch issue that appeared. Turns out the exhaust and cats are fine. But I was told I had a bad throw out bearing after a test drive with the tech, i had been hearing odd sounds coming from the transmission whenever i stepped on the clutch but i just figured it was an MT-82 being and MT-82. I took it back this morning to do the clutch system and when we dropped the transmission to service the clutch system I was hit in the face with that rotten egg smell. It turns out the rubber boot on the throw out bearing was ripped and clutch fluid was getting out. That nasty smell I was getting when I got on it was my clutch fluid being burned. The clutch looked fine and had about 80% life left on it (I just changed it last year), just the throw out bearing looked horrible. I'm just going to service the clutch since the trans is already out. Thank you all for the help, and F*ck Ford for not being able to make a competent clutch system for this powertrain.

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