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Mattbloke

Strong carbon monoxide smell on starting - 2002 Yaris 1.0

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When I start up my Yaris from cold, there is a really strong carbon monoxide smell - bad inside the car but really bad outside it.  Most of this must be coming out of the exhaust but why so strong inside the car?

Any thoughts please?

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Carbon Monoxide has no smell so it must be something else you are smelling.

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Carbon monoxide is colourless and odourless.

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Doh! Good point.  Really bad exhaust gas smell then.

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It could be the exhaust is blowing somewhere near the front of the car, or even the manifold has rusted through into a hole, which does affect Mk1 models where the manifold is on the front of the engine and is subjected to water spray coming through the front grille, allowing gases to enter the car through the ventilation system. Usually this would mean the car becomes very noisy, or has a loud ticking noise on hard acceleration which is a good indication that the manifold has become holed.

In cold weather, exhaust gases do smell strong from the exhaust in the first 30 seconds or so after a cold start of the engine, as the fuel mixture is enriched and the catalytic converter does not function to clean the exhaust gas until it heats up to working temperature.

In general though, any strong smells of exhaust gas in the cabin would indicate a hole in the exhaust, or some other damage to it, allowing the gases to escape but this would usually be heard as a loud blowing noise when revving the car, and the louder the noise, the further towards the front of the car that the exhaust is failing. If the manifold has developed a rusty hole, this would usually be heard as a loud ticking or clicking from the front of the engine on hard acceleration, as it would usually only be the noise from one particular cylinder on its exhaust stroke - but you would still be able to smell the escaping gases if they are drawn into the ventilation system. If you are in any doubt about the exhaust system, dont take the risks, take the car to a garage like Kwik Fit and ask them to check the whole exhaust system as you can smell fumes in the cabin.

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Also, check to see if the engine management warning light (MIL) is on (its a yellow warning light in the picture of an engine), as if it is, then there could be a problem with the engine's sensors causing the engine to run too rich, causing a strong exhaust smell. A blowing exhaust in front of the cat can often also turn on the MIL.

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 Not enough info.

 Are you parked outside in the open air or in an enclosed space or garage? Is the ventilation system in the 'on' mode? Is the exhaust leaking/blowing? Does this only happen when it's breezy or windy?

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Chances are: the catalyst at the front of the exhaust has corroded and has holes in it.. Either the welded seams runing the length of it have split or the flanges mounting it to the exhaust pipe, (Son's  one of similar age had that)

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Thanks for all of the suggestions/info.  I will check it out as soon as I get a chance to get it up on my axle stands.

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