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O2 Sensor question

Old 08-19-2019, 08:57 AM
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Originally Posted by NHGuy View Post
Here is some theory about fails, one of which is rich fueling
https://www.nzefi.com/bosch-lsu-wide...-applications/

But I never had an issue til I let the boat sit for an hour or so, on the next start up the gauge read full lean, and never came back.
I'm going to do a test today where the sensor is removed from the exhaust, powered up and fed with brake cleaner or propane from a lighter. It's supposed to go rich when you do that. But at the same time they warn you that the thing gets so hot it can cause combustion. So fire extinguisher.
My AEM did the same thing after a couple fire ups. Pulled sensor, brake cleaner test, stayed full lean. Bought new Bosch 4.9 sensor, brake cleaner test, still full lean. WTF? AEM said send back the setup. Gauge was the problem. They performed a recalibration of gauge and it's been working great for last 20ish hours. Sensor shows no signs of moisture or water.

Water is mixed into exhaust 1" before transom. 230/238 116+4 cam
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Old 08-19-2019, 09:23 AM
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Originally Posted by NHGuy View Post
OK, I am convinced. I was spouting a lot of car based theory. Which doesn't always fly in our marine environment.

Yesterday I got the chance to run the AEM 30-0300 UEGO gauge with factory calibrated Bosch LSU 4.9 wideband sensor.
It idled out and ran 20 minutes to a cove we hang at. Readings were consistent and appeared correct. 13.7 cruise, 11.9 to 12.4 on the secondaries. I'd call that good. Maybe I can go up one size on primary jets to richen the cruise. My carb place sent me some plus 1/ minus 1 jets. So,yuh maybe.
My idle mix is rich, so I'll get out there and back that off. And that may have contributed to my sensor shutting down.
Here is some theory about fails, one of which is rich fueling
https://www.nzefi.com/bosch-lsu-wide...-applications/

But I never had an issue til I let the boat sit for an hour or so, on the next start up the gauge read full lean, and never came back.
I'm going to do a test today where the sensor is removed from the exhaust, powered up and fed with brake cleaner or propane from a lighter. It's supposed to go rich when you do that. But at the same time they warn you that the thing gets so hot it can cause combustion. So fire extinguisher.

I hope and think that I am getting condensation in my exhaust. It ran in the yard twice, no issues. Including normal exhaust water. My exhaust flappers are gone, and I have GGB exhaust inserts right where the tails go into my 4" rubber hoses. So maybe I need to take out the inserts.
But I am guessing that the condensation could have caused my issue. So if the sensor is dead, which I expect, I will probably get a fresh sensor and that extender elbow that I ripped before.
That's an instant bolt up, plus it gets the sensor away from the wet. instead of having a bung put in at the angle that AEM specifies.
Your tail pipe flappers are gone? Is that correct? It’s very possible that your taking waves up the pipes when you’re just sitting there.

The GGB inserts have a reputation for decreasing reversion. It seems backwards to me but I read it on the internetz so it must be true.
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Old 08-19-2019, 09:41 AM
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I've seen/heard the same with Lightning headers. I had them dry to the tip in a previous boat and couldn't believe how wet the collectors would get. I now run CMI's that are +6" tall dry to the tip - they stay nice and dry. My engines are N/A with pretty big cams.

I ran Innovate/Bosch widebands from 2008-2013 and Holley EFI with the standard Bosch widebands from 2013-present. Straight into the bung... Never had to replace a single sensor... I hear good things about the NTK's, but haven't had a reason to change.
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Old 08-19-2019, 09:53 AM
  #34  
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Originally Posted by Baja Rooster View Post


Your tail pipe flappers are gone? Is that correct? It’s very possible that your taking waves up the pipes when you’re just sitting there.

Which brings up a good point, some do use the term reversion when they should use the term intrusion.
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Old 08-19-2019, 09:53 AM
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NTKs are definitely more hardier than Bosch.
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Old 08-19-2019, 11:27 AM
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Yup, my new flappers are not in the boat, sitting on my desk. I hope it's a problem with the parts. I'd love it if I had a solution like Ryan. I'll order a sensor...
On the intrusion question, I was sitting in a cove. No waves, I mean zero. But I don't rule out that water could condense in there.

Last edited by NHGuy; 08-19-2019 at 11:42 AM.
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Old 08-19-2019, 12:25 PM
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Originally Posted by tgorbett View Post
Smitty,
Have any experience with the KE cast headers with regard to reversion issues?
I hear good things about them but have no first hand experience. Im probably going to go to them on my Scarab once I decide for sure what Im doing. As of right now, leaning towards 522's w 13-1 or so compression, edelbrock proflow4 intakes but still in the planning stage.
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Old 08-19-2019, 12:31 PM
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Originally Posted by SB View Post
Sure is interesting. I fortget his name, but he had a build several years back with real mild cam and was sucking water bad with those headers.

Would love to get header dimensions (ID's and lengths) + rate of fall and a good pic of how water is introduced into the exhaust stream.
Was the guy from Va that had a blown single and a big cruiser that had all the distributor problems, rob sheffield. Stock 500hp cam, reverted water to point it also killed all o2 sensors until he put them in header tubes
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Old 08-19-2019, 12:37 PM
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Originally Posted by articfriends View Post
Was the guy from Va that had a blown single and a big cruiser that had all the distributor problems, rob sheffield. Stock 500hp cam, reverted water to point it also killed all o2 sensors until he put them in header tubes
NO.
I'll think of it sometime, hopefully today. I have sometimers and mantimers kicking in.
He was on this board for a few yrs trying everything and everything. He started from no/little knowledge of engines to a good amt during that time period.
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Old 08-19-2019, 12:40 PM
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Oh, I think his name was Budman. Smaller boat, single, 502, AFR heads, Lightning headers, small hr cam..... I'll search him in a bit.

Phew.......my brain was cramped up trying to remember.
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