Ammonia/Cat Piss Smell

[bmrboi2]

I have this smell coming from my exhaust. I have scoured around and found some of the most ludicrous reasoning from idiots who don't read the actual issue. This is coming from my exhaust at Idle after a cold startup and its only on rare occasion. It doesn't appear to be environmental just totally random.

It's not inside the cabin, it's not coming from the vents, it's not under acceleration that I can notice (Followed my husband one day) I am just hoping that it's nothing wrong.

There isnt anything wrong with the cooling system or the ac system....aside from thrust arms needing replacement and new rear brakes....not a friggin thing wrong with this vehicle. Any Ideas?

The one thing that I saw seemed intriguing is to change gas brands. I have been using Costco gas regularly in all of my vehicles for years and never had an issue like this. The 5er and the old X5 (Same 3.0l 6) never had a smell like this, ever. I'm stumped.

[brucemillar]

Most bad exhaust smells come from, either the cats (usually rotten egg smell) and or the fuel.

Transmission fluid is known to smell of cat piss when warm/hot.

Are you certain that you do not have a transmission leak onto your exhaust. The exhaust would very quickly burn it off when the car is hot. At start up it will cook nicely for a few minutes before it gets hot enough to vaporize it.

I would be tempted to get under the car while it is cold and run your hand along the top of the exhaust to see if there is any trans fluid pooling there. Also have a general look to see if there is any evidence of dripping/pooling near the exhaust tunnel, lying on heat shields etc.

Please do report back.

[crystalworks]

Originally Posted by bmrboi2

The one thing that I saw seemed intriguing is to change gas brands. I have been using Costco gas regularly in all of my vehicles for years and never had an issue like this. The 5er and the old X5 (Same 3.0l 6) never had a smell like this, ever. I'm stumped.

Just an FYI on Costco fuel. It's not a top tier fuel, which is normally not a big deal. But a few years ago we had a rash of cars come into the shop with fuel pump failure. The only common thread was the fuel. Took doing the fuel pump multiple times on one vehicle for it to be narrowed down. Turned out the Costco fuel was causing pump failures for some reason. Either it could not keep the pump cool enough (fuel is part of cooling for the pump) or something else was afoot.

At any rate, Costco must have had other reports from other shops as well and stepped up and paid or reimbursed the owners of any cars that were affected.

Again, just an FYI. I have no idea if it's contributing to the smell, but I try to avoid Wal-mart, Sam's, and Costco fuel stations if I can. I use Shell, Exxon, or HEB fuel (HEB is not top-tier, but I've been using it for years with no probs and it's convenient ).

[Aquamania]

Well I can tell you one thing, where I live we have LOT'S of stray cat's. I have caught them "marking" on my trucks.

[ryan5034]

I have the same smell on occasion. I'm not really convinced anything is wrong. I do use Costco gas if possible. It's 92octane most in town is 91. Could be a function of ethanol I suppose.

[Thecastle]

I have this same issue. Strong smell of ammonia from the exhaust pipes. Never had a car with this issue. Mine is a x5m for the record and has the s63 engine.

My older x5 4.8i did not do this. Nor does my Mini Cooper or my diesel 335d. I buy gasoline from the same shell station.

It's strange.

[bfeng]

I get that ammonia smell on and off, regardless of cold or warmed up. I think it is just something that comes the urea injection system (system probably were on the high side to ensure complete conversion of any NO. When I am hooking up my hitch it's quite noticable.

[Thecastle]

Originally Posted by bfeng

I get that ammonia smell on and off, regardless of cold or warmed up. I think it is just something that comes the urea injection system (system probably were on the high side to ensure complete conversion of any NO. When I am hooking up my hitch it's quite noticable.

This is something were noticing on gasoline cars which don't have urea injection. My gasoline X5M has cat piss smelling exhaust my diesel smells like nothing. If your diesel has a cat piss smell something may be off, as mine never smells. Other than a faint diesel smell when cold.