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Date:         Sat, 30 Aug 2008 12:33:50 -0400
Reply-To:     Dennis Haynes <d23haynes57@HOTMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
Comments:     RFC822 error: <W> MESSAGE-ID field duplicated. Last occurrence
              was retained.
From:         Dennis Haynes <d23haynes57@HOTMAIL.COM>
Subject:      Re: When the O2 sensor cools down...
Comments: To: pickle vanagon <greenvanagon@gmail.com>
In-Reply-To:  <91c8f9760808300923s5b4fd6e2ye38d6b3c31582bd6@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"

The decision for the ecu to go closed loop is based on temperature, not whether or not the O2 sensor is creating a usable signal. On a warm engine, the ecu will still do the fuel cut off even if the O2 sensor is missing. This is actually a good thing as you don’t want the engine to get too cold.

Dennis

-----Original Message----- From: pickle vanagon [mailto:greenvanagon@gmail.com] Sent: Saturday, August 30, 2008 12:24 PM To: Dennis Haynes Cc: vanagon@gerry.vanagon.com Subject: Re: When the O2 sensor cools down...

Thanks for all of the answers! So now, the point of my question (and this is really the end), was that I was curious if this fuel shutoff still works once the o2 sensor has cooled down. I'd be driving down a really long hill with the van in gear, and at the top, I'd be happy about the fact that I was consuming zero fuel, and then, once I had gone far enough the o2 sensor was cool and reading flat, I was wondering whether I was still consuming no fuel, or whether I was now consuming fuel after all. If the engine braking fuel shutoff still works after the o2 sensor cools, it means it's still most fuel efficient to stay in gear. I guess if it doesn't, you should be better idling on the way down, or shutting off the engine.

On Sat, Aug 30, 2008 at 2:50 AM, Dennis Haynes <d23haynes57@hotmail.com> wrote:

No, fuel cut off only occurs when the engine is warmed up enough for closed loop operation.

Dennis

-----Original Message----- From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of pickle vanagon Sent: Saturday, August 30, 2008 1:19 AM To: vanagon@GERRY.VANAGON.COM Subject: Re: When the O2 sensor cools down...

On Fri, Aug 29, 2008 at 10:25 PM, Dennis Haynes <d23haynes57@hotmail.com>wrote:

> Engine braking is strictly a function of the closed throttle causing high > manifold vacuum as the engine is being driven by the wheels. Yes, engine > braking is caused by vacuum, not compression. >

What I meant to ask, is whether the ECU still shuts off fuel to the injectors above the cutoff (I thought it was 2000rpms?) at zero throttle even if it is not yet in closed loop mode. It makes sense that it would, I just can't verify this with the mixture meter since the o2 sensor is nonfunctional at this point.


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