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#4384713 - 04/20/17 10:46 PM Would a leak at an oxygen sensor burn valves?
NoNameJoe Offline


Registered: 06/03/15
Posts: 267
Loc: New York
There's an age old (possibly myth) telling that open exhaust systems or systems with leaks would burn exhaust valves.

If there was a loose oxygen sensor such that a small amount of exhaust possibly blew past it, how likely would it have messed with things? If the oxygen sensor was totally gone would that change enough back pressure to damage valves?

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#4384721 - 04/20/17 11:00 PM Re: Would a leak at an oxygen sensor burn valves? [Re: NoNameJoe]
dishdude Offline


Registered: 11/14/08
Posts: 7826
Loc: Phoenix
No way.
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#4384741 - 04/20/17 11:40 PM Re: Would a leak at an oxygen sensor burn valves? [Re: NoNameJoe]
BrocLuno Offline


Registered: 09/06/15
Posts: 4315
Loc: Kalifornia Kollective
No. Burnt valve are due to lean condition. That's intake leak, bad injector, or something along those lines ...


Edited by BrocLuno (04/20/17 11:41 PM)
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#4384886 - 04/21/17 08:20 AM Re: Would a leak at an oxygen sensor burn valves? [Re: NoNameJoe]
daves66nova Offline


Registered: 04/11/04
Posts: 3504
Loc: los angeles
Originally Posted By: NoNameJoe
There's an age old (possibly myth) telling that open exhaust systems or systems with leaks would burn exhaust valves.

If there was a loose oxygen sensor such that a small amount of exhaust possibly blew past it, how likely would it have messed with things? If the oxygen sensor was totally gone would that change enough back pressure to damage valves?
If the o2 sensor was indeed messed up, it probably would make the car run richer. I don't see where people get this about back pressure. If anything, a leak in the exhaust would vent exhaust gasses out, resulting in LESS backpressure in the system. but also, depends on your year car,such as a sensor after the rear cat, which might throw off the mixture too.
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#4384899 - 04/21/17 08:36 AM Re: Would a leak at an oxygen sensor burn valves? [Re: NoNameJoe]
KrisZ Offline


Registered: 12/23/06
Posts: 6877
Loc: Toronto, Canada
If the oxygen sensor fails, and the system cannot determine the appropriate A/F ration, it will switch to open loop and pre-programmed maps. So when that check engine light is on, the ECU is already ignoring the signal from the oxygen sensor, no damage will happen.

Exhaust valves being too tight, that's when they are super quiet, is usually the cause of them burning up.


Edited by KrisZ (04/21/17 08:37 AM)
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#4384944 - 04/21/17 09:33 AM Re: Would a leak at an oxygen sensor burn valves? [Re: NoNameJoe]
HerrStig Offline


Registered: 08/24/11
Posts: 9560
Loc: Boston, MA
There maybe some truth to it with respect to air cooled engines running lean. The vaporization of
fuel has a cooling effect. On a liquid cooled, emission controlled car engine it's not an easy answer. Running retarded timing was also said to cause burned valves. The switch from leaded fuel was as hard on exhaust valves.

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#4385495 - 04/21/17 08:35 PM Re: Would a leak at an oxygen sensor burn valves? [Re: NoNameJoe]
circuitsmith Offline


Registered: 12/17/09
Posts: 572
Loc: Wash, DC
When a pressure wave goes down the exhaust pipe and reaches the end it can return as a rarefaction (suction) wave.
So air can be periodically sucked into an exhaust leak.


Edited by circuitsmith (04/21/17 08:36 PM)
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#4385660 - 04/22/17 01:49 AM Re: Would a leak at an oxygen sensor burn valves? [Re: NoNameJoe]
punisher Offline


Registered: 09/11/04
Posts: 2414
Loc: snowblind in TX
There was talk about engines that had really short primaries that just dumped to atmo that it was possible for reversion to potentially suck in cool air over a hot exhaust valve and cause warpage. Like a lot of things, I have heard of it, but never seen it.

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