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Rotten cat odor

2K views 21 replies 18 participants last post by  Yadkin 
#1 ·
Smell started at 18K miles (now@25K). Only mod is CAI/ 93 octane tune and American Thunder Flow Master axle back...That's it.

Cat temp control update tune has been installed and it went away for a few miles...it's back.

It happens every time it's rev'd past 6000+ RPM's (never past red line). After a 120-150 MPH run, windows have to come down to let rotten odor out...goes away quickly.

Immediately after the :nono:...spirited drives. I get out to see if there is any smoke in the engine compartment...nothing.

Other problem...nothing to do with spirited drives. I use this car for estimating parking lot repairs...if it idles for more than 5 minutes. Check engine light comes on (lean code). Code is erased and continue on my way.

Rather than messing around with FORD Warrany rejection...seriously considering letting someone else inherit this problem...no control of who buys it after it's traded in.

Got rid of my 2010 GT500, so I could drive a Stang without worrying about depreciation. Now, I have GT aggravation :yup: need a solution so I can continue to drive it for a while...HELP or it's gone!

Don't even mention that I need another car for estimating its my company car preference...to hell with econo boxes.
 
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#3 ·
i would get an off road mid pipe. i am 100% sure that you wont have the rotten smell anymore.
 
#18 ·
^^ This..................
 
#6 ·
Smell started at 18K miles (now@25K). Only mod is CAI/ 93 octane tune and American Thunder Flow Master axle back...That's it.

Cat temp control update tune has been installed and it went away for a few miles...it's back.

It happens every time it's rev'd past 6000+ RPM's (never past red line). After a 120-150 MPH run, windows have to come down to let rotten odor out...goes away quickly.

Immediately after the :nono:...spirited drives. I get out to see if there is any smoke in the engine compartment...nothing.

Other problem...nothing to do with spirited drives. I use this car for estimating parking lot repairs...if it idles for more than 5 minutes. Check engine light comes on (lean code). Code is erased and continue on my way.

Rather than messing around with FORD Warrany rejection...seriously considering letting someone else inherit this problem...no control of who buys it after it's traded in.

Got rid of my 2010 GT500, so I could drive a Stang without worrying about depreciation. Now, I have GT aggravation :yup: need a solution so I can continue to drive it for a while...HELP or it's gone!

Don't even mention that I need another car for estimating its my company car preference...to hell with econo boxes.

Of my many problems with my 2011 GT when new, I too had an oder. I brought it to the dealer who later found a burning sticker on one of the exhaust pipes (or so they said). Apparently, when the pipe got warm, the sticker/adhesive would heat up and burn, sending a foul smell (smelt like something died) around the vehicle.

The dealer removed the sticker/adhesive and sure enough the smell went away.

I would do a quick check to see if you have a similiar issue.
 
#7 ·
A sticker could be making that smell...WHAT!?!?!?! Where is this sticker I must remove it.
 
#14 ·
Mine does it with stock tune and with my Bama tunes. I think its just the cats being cooled with extra fuel.
 
#20 ·
Thanks for all responses, been on vacation...^^^^exactly what it smells like.

It's a lot better since STEEDA revised map (cat temp control). But the odor has not gone away completely. Not worried...car runs fine under normal driving conditions.

Car is daily driven 200+ miles a day with at least one-two 120+mph runs :yup:.

Trying to decide whether to keep it or dump it.
 
#19 ·
I think I would be more worried about the lean code than anything. Something is not right there, maybe they forgot to load the correct values for your CAI. Return the car to stock (tune and CAI) or talk to the guys at Bama about another tune.
 
#22 ·
Old school analysis:

The described odor used to be common when catalytic converters just came out, and usually occurred during cold starting, and older cars after hot running. These were carb-era cars and the smell was undoubtedly due to inefficient fuel delivery with fuel not completely burned in the engine and forming deposits on the converter.

You've described long idling, lots of daily driving and a custom tune followed by Autobahn speeds. I suspect the tune may be the cause.
 
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