Wide band real lean at idle with dumped exhaust ?? - Ford Mustang Forums : Corral.net Mustang Forum
 
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post #1 of 10 Old 04-27-2015, 08:50 PM Thread Starter
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Wide band real lean at idle with dumped exhaust ??

My wide band is in the h-pipe just past the pass. shorty header and I am getting some weirdly lean #'s like 22-23, at idle, I have 2.5" h-pipe and 3" ultra flows into dumps, Does this sound typical with a short exhaust system ?? I only use this wide band once in a great while and used to be able to just run it up in a tail pipe with success so I am suspecting my sensor is getting fouled, it does clean up at higher rpm's and seems logically correct. My unit is a dyno type big box wbo2 system and I just ordered a new innovate MTX to replace it ??

As a secondary question, will I get more stable or accurate wbo2 #'s if I place my bung in a selected leanest header tube rather than the collector ??


First car when I turned 16 was a Brand New 1979 5.0 Coupe and my current car of choice is still a 1979 5.0 Coupe, just not new anymore...

Last edited by 1979 5.0 Coupe; 04-27-2015 at 08:52 PM.
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post #2 of 10 Old 04-27-2015, 09:04 PM
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You want the bung as close to the collector as possible.

On a preOBD2 setup I have found it quite normal to be lean at idle or when decelerating with foot off the gas. However, it should go to 14-15 once you start to put load on the motor.


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post #3 of 10 Old 04-29-2015, 03:28 PM Thread Starter
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My H-pipe has bungs in both sides behind my shorty headers but they are at the 5 and 7 o:clock positions, I know this is less than perfect but I really don't want to pull the full exhaust off to more optimally relocate them to the top side. Can someone give me feedback as to what to specifically expect in terms of accuracy and sensor life ??

First car when I turned 16 was a Brand New 1979 5.0 Coupe and my current car of choice is still a 1979 5.0 Coupe, just not new anymore...
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post #4 of 10 Old 04-29-2015, 03:58 PM
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I think your placement is fine.
Lifespan is fairly long as long as you don't run leaded fuels.

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post #5 of 10 Old 04-29-2015, 05:26 PM Thread Starter
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I have never priced a replacement sensor ?? any idea, worst case on cost...

First car when I turned 16 was a Brand New 1979 5.0 Coupe and my current car of choice is still a 1979 5.0 Coupe, just not new anymore...
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post #6 of 10 Old 04-29-2015, 05:37 PM
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$100

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post #7 of 10 Old 05-02-2015, 11:44 PM
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If you have more than three feet of exhaust after the O2 sensor and there are no leaks, then pipe length is not likely the issue. Overheating will hurt a WBO2 sensor and so will running the engine with no power to the sensor.

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Originally Posted by 2001sleeper View Post
On a preOBD2 setup I have found it quite normal to be lean at idle or when decelerating with foot off the gas.
That's because just about, if not all production digital EFI systems made in the last 30+ years shut the injectors off during decel. It is a fuel saving measure that also increases engine braking.

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post #8 of 10 Old 05-02-2015, 11:55 PM Thread Starter
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Quote:
Originally Posted by GT Madness View Post
If you have more than three feet of exhaust after the O2 sensor and there are no leaks, then pipe length is not likely the issue. Overheating will hurt a WBO2 sensor and so will running the engine with no power to the sensor.



That's because just about, if not all production digital EFI systems made in the last 30+ years shut the injectors off during decel. It is a fuel saving measure that also increases engine braking.
Carburators started doing that the first time one was bolted on a car, they are amazing devices

Thanks for the info guys, I got a new Innovate mtx-l to install, we'll see how it goes. I may remount the sensor on top, I had an ebay dude stiff me on some final parts and f'ed up my weekend of testing driving in beautiful spring weekend weather so I got some extra time to tinker with it.

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post #9 of 10 Old 05-03-2015, 01:37 AM
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Quote:
Originally Posted by 1979 5.0 Coupe View Post
Carburators started doing that the first time one was bolted on a car,
If you're referring to the shutting off of fuel during closed throttle, no they didn't.

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post #10 of 10 Old 05-03-2015, 08:32 AM Thread Starter
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Ya, your technically right. I was just generalizing since they take the fuel down to nill with no electronics. After 20 years of hot rodding mustangs I still laugh at the posts on this site and how most people these days think carbs are old school but they fail to realize that most all of the tuning discussions revolve around efi that is spitting farting surging and bogging and having to take them to a tuner to make them drivable. I have had the original speed pro, then the first of the fast offerings, Big Stuff and MEFI on turbo and blower race cars and non of them were ever impressive and sorted out such that I would have liked to see modern electronics after decades development. I am studying the newest generation of efi and wondering if it is worth trying again. Wondering if any of these new self learning EFi kits really work. I have learned pretty well how to use and tune them over the years but still like my carbs. I did have good success with a Dynojet Power Vision that self learned on my Harley.


First car when I turned 16 was a Brand New 1979 5.0 Coupe and my current car of choice is still a 1979 5.0 Coupe, just not new anymore...

Last edited by 1979 5.0 Coupe; 05-03-2015 at 08:35 AM.
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