Mateofeo

Hello everyone,
I have a 2007 F150 4X4 with the 5.4L. 114k miles
I keep getting a weird smell in the cab and outside my truck and the only thing it smells like is propane. Its been doing this for over a week now and I cannot stand it. I drove by my neighbor yesterday and he thought there was a propane leak in the area but it was coming from my truck. I can't find a source of the smell, but it seems to be coming somewhere from the engine bay/under the wheel wells. Nothing I can think of smells like propane (burning oil, coolant, trans oil etc) Anyone have any ideas?

Tothemax

Crawl under it and look for leaks. I can't think of any fluid that would smell like propane

Mateofeo

I have. There is no leaks that I can see and yeah I can't think of anything that smells like propane. I am stumped

RLXXI

Rotten egg/sulfur smell? When cats are being fed by an overly rich exhaust mixture. Other than that do you have a CNG system on your truck? Would be easy to tell as a good portion of the cargo area would be taken up by the tank.
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Mateofeo

That was something that crossed my find but it really does not smell like rotten eggs. I put my face right behind my muffler and smelled nothing. I also just passed smog less than 2 months ago.

But how is there a way to see if the cats are going bad?

Also no CNG lol

RLXXI

When they go bad your check engine light will pop on and a code will set. I have seen instances where they were still working but had that smell and the only cure was replacing them.
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rednblues

And bad fuel can cause this too smell too.

Otherwise, put a load on it and have someone stand near the tail pipe. It will be obvious.

Mateofeo

I have used gas from several gas stations over the passed 2 weeks.

I put my face right behind the muffler. Nothing was obvious

Mateofeo

No check engine light. Sadly.

Stu Cazzo

you have a partially plugged catalytic converter.
Its not propane smell...its rotten eggs smell or award winning bad fart smell.