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White stuff around the 02...

SleepinGVR4

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Feb 12, 2003
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Danville, Pennsylvania
I have this white stuff between my 02 housing and the turbo. Is this a sign of an exhaust leak? Could explain why my car is running like dog poop.
 

WaRrIoRs16

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Mar 23, 2008
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373
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Ferndale, WA
Both my 1g and my galant had/have maxed fuel trims indicating I was lean. The exhaust manifolds both had cracks in them and I could see white discoloration around the cracks. Also my o2 sensors were white when I pulled them out. So I would say an exhaust leak would cause the the white stuff, and I would assume it could cause your car to run poor due to the o2 sensor not seeing all of the exhaust that is coming out of the motor but I'm not positive.
 

SleepinGVR4

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Danville, Pennsylvania
The problem I'm having is anything 10psi and over it knocks and if I really hammer on it, lots of black smoke exits my tail pipe. If I do have an exhaust leak before the 02 sensor, I figured the ECU sees that and dumps more fuel because it thinks my car is running lean.
 

Brunoboy

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San Bruno,CA Home of SFO
My car does that too after low boost, does your car hesitate at all?
 

steve

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Quoting SleepinGVR4:
If I do have an exhaust leak before the 02 sensor, I figured the ECU sees that and dumps more fuel because it thinks my car is running lean.



Thinking out loud here, the O2 sensor is not trying to detect the volume of exhaust gases, so it doesn't care about the lost volume of exhaust gases due to the leak. Plus, if there is an exhaust leak it isn't going to be just the O2 leaking out, or just the O2 staying in the exhaust. The gas as a whole will escape, and the ratio of oxygen to other gases should be unchanged. So I don't see how an exhaust leak would cause the ECU to dump more fuel, as long as the O2 sensor is seeing a representative sample of exhaust gases. No?
 

SleepinGVR4

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Quoting steveGLS:
Quoting SleepinGVR4:
If I do have an exhaust leak before the 02 sensor, I figured the ECU sees that and dumps more fuel because it thinks my car is running lean.



Thinking out loud here, the O2 sensor is not trying to detect the volume of exhaust gases, so it doesn't care about the lost volume of exhaust gases due to the leak. Plus, if there is an exhaust leak it isn't going to be just the O2 leaking out, or just the O2 staying in the exhaust. The gas as a whole will escape, and the ratio of oxygen to other gases should be unchanged. So I don't see how an exhaust leak would cause the ECU to dump more fuel, as long as the O2 sensor is seeing a representative sample of exhaust gases. No?



That's what I thought Steve. But I was reading something over on Tooners and one of the Mods said that if there is a exhaust leak before the 02 sensor, the 02 sensor sees the fresh air getting in as the mixture being lean so it adds more fuel. According to the guy on Tuners that makes the factory 02 sensor read funny, making the fuel trims never even out and makes your wideband read leaner than it should when in reality my car could be running rich.

That's what I got out of it anyway. I could be way off. Maybe Jeff O. could clarify.
 

steve

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Good point, if fresh air is being pulled in and then sent down the exhaust somehow. /ubbthreads/images/graemlins/idea.gif
 

misterfixit

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Aug 4, 2004
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Midlands, UK
Exhaust leak = less efficiency in the turbine, so less power transmitted to the compresor. ECU still sees the load demand and throttle, and tries to make up the difference with fuel etc.. but as the efficiency is not there it can never catch up.

Rich
 

Junior392

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Sep 3, 2008
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Saratoga County, New York
On the subject of thinking out loud. Have you thought about blow by (through) while under boost. When i pulled my old head off of my car my valve stem was coated "white". As well at the exhaust port having streams of "white" along side the walls. This was caused by the air in the combustion chamber getting by the exhaust valve which wasn't seated properly.
 

SleepinGVR4

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Danville, Pennsylvania
Quoting misterfixit:
Exhaust leak = less efficiency in the turbine, so less power transmitted to the compresor. ECU still sees the load demand and throttle, and tries to make up the difference with fuel etc.. but as the efficiency is not there it can never catch up.

Rich



That would probably explain why my car feels slow. The funny thing is, I have a gasket between the turbine housing and 02 housing. It was new then I put my engine together. But I've come to suspect that the flange on the Megan Racing 02 must be warped.
 
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