I've noticed for over a month now that I get a strong smell of fuel inside the car when driving slow or still and i hhave to open the windows. My exhaust also gives a popping sound and it idles a little rough. A friend checked my spark plugs and two were wet, but otherwise fine. My mot just failed due to emmissions, high lambda reading, other two were normal. I have put a cataclean through it as advised and patched a little hole in the exhaust and 'thrashed the life out of it' and it reduced the lambda reading but not by enough.

I have recently had a full service, (oct) and a new coil pack. A diagnostic also showed a faulty coolant temperature sensor, so that has also been changed and it's also had new headgasket around 18 months ago. It's really frustrating because it drives so well and everything passed the mot but that lambda reading. And obviously the fuel smell is a concern. I must add that my fuel consumption is fine too, I get the right amount of mpg. Do all this things indicate what is wrong? In the garage I went to they were scratching their heads, as they thought it could be the coils but as its been done they didn't give me any other indication what it could be, and they didn't seem concerned when I told them about the smell of fuel I get. They were very busy and just sent me on my way with my failed mot cert. I feel quite vulnerable as I'm so clueless they could say anything needs fixing and I'd believe them as this has happened to me before, I'd like to go back with a few possible solutions in mind so I'm as knowledgable as possible before I hand over any money for repairs.

Thank you in advance!

  • Probably fuel being ejected out the back. Is there smoke at all? Try take a close look while someone else revs. Had a problem with my car smelling like fuel/lawn mower and it was pretty much because a lot of unburnt fuel is sent out the back (old car, old stem seals I fear).
    – insidesin
    Commented Feb 14, 2019 at 6:19

2 Answers 2


Assuming the head gasket has been checked to make sure oil/coolant isn't leaking into the combustion chambers it sounds to me like the Cat is failing. I had a Vauxhall Astra that had two lambda sensors fail, a coil pack fail and also had a petrol smell to it. Each time i had a failure i questioned was the main cause the catalytic converter but each time i was told no.

In the end the cat failed badly enough to show up during diagnostics when yet another engine management light came on. So forgive me if i feel i was right all along lol.


The one time I had a consistent fuel smell in the car , it was a very small leak at a rubber hose to a fuel injector . Not enough to drip, just a wet surface. The fix was to tighten a clamp.

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