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340 catalytic overheating


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Has anybody had a problem of overheating of their cat engine when idling due to vapourization from the top exhaust mani entering the water distribution center and thus the engine causing overheating?

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Oxygen sensor......?

If sensor determines that a leaner mixture is required, then much higher exhaust gas temps are possible.

I'm suspecting that it runs great at W.O.T ( O2 sensor readings disregarded ).

Is there any unburnt fuel at any rpm? This can cause the Catalytic converter to overheat .

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Oxygen sensor......?

If sensor determines that a leaner mixture is required, then much higher exhaust gas temps are possible.

I'm suspecting that it runs great at W.O.T ( O2 sensor readings disregarded ).

Is there any unburnt fuel at any rpm? This can cause the Catalytic converter to overheat .

it actually runs great all the time no probs at idle or thru the entire rpm ban, it has only happened 3 times in 60 hours ( but the temp spikes happen very quickly , sometimes only a few degrees occasionally 177,185,203) but from what your saying ...the O2 sensor would be registering a lean mixture at idle and thus the ecm would dump more fuel in resulting in unburnt fuel and hotter cat temps at an idle?

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I would suspect faulty O2 sensor if it were doing it all the time at idle but as it isnt I'll have to think a little more. The mixtures are normally cycled lean/rich at low rpm but ecm wont dump more fuel .

Was just asking if there was unburnt fuel to rule out other faults.

but from what your saying ...the O2 sensor would be registering a lean mixture at idle and thus the ecm would dump more fuel in resulting in unburnt fuel and hotter cat temps at an idle?

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[quote

Was just asking if there was unburnt fuel to rule out other faults.

how would i determine if there was unburnt fuel.........there is no smell i can detect but then the cat would burn any of it.....may gas consumption is so much better than my old 350 carbed engine

thanks for your input :)

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