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Fasstdak
Dodge Dakota
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2/07/2007
22:49:38
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 Subject: RE: map sensor question
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Have them look at these items:
MAP BARO Reading
MAP Voltage
Coolant Temp
Fuel Adaptives (the full chart - all 26 cells, not just a single entry)
Write down the adaptives and the other items and feel free to email me with them.
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Mike stager
Dodge Dakota
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2/07/2007
23:10:14
| RE: map sensor question
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Will do. Thanks for the input.
One thing, would you recommend the dealer to look at this over a regular mechanic? And what does the dealer typically charge for a scan?
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Fasstdak
Dodge Dakota
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2/08/2007
00:15:04
| RE: map sensor question
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I'm partial to dealer techs as they are trained to look at these readings properly. Not saying than a small shop tech can't read them, they just don't look at them on a daily basis on these vehicles.
Average shop charge would probably be for 1 hour ($90 in most cases - depends on the area though).
A good tech can scan, read, interpret, and give a diagnosis with fix in under an hour.
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Mike Stager
Dodge Dakota
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2/09/2007
01:41:10
|  RE: map sensor question
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Excellent. I have a Dodge Dealership right up the street from my work, and a mechanic that works for us and has the equipment but is the type that "promises" to take a look at your car, but is like pulling teeth to actually get him to do it. I'll probably just drop it off at the dealer and see what they have to say.
One thing of note, I don't have the cat on the truck at them moment...short of the dealer telling me that I need one ( plan on it anyway ), they should still be able to tell me what is going on regardless of having a cat or not. And lastly, do you, having seen plenty of these vehicles....know why I have one O2 sensor after the cat and nothing before the cat on a 97, when I'd expect to have the O2 sensor before the cat if I only had one...Seems like it must be a weird single year thing for the first OBD2 trucks....
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Fasstdak
Dodge Dakota
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2/09/2007
07:02:14
| RE: map sensor question
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You should have one in front of the cat - it may be up towards the exhaust manifold (either left or right)...but it will have one - PCM requires it.
All vehicles require one in front of the cat - they won't run right (or at all) without it.
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Mike Stager
Dodge Dakota
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2/09/2007
20:41:50
| RE: map sensor question
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Well, I've been up and down the Y pipe and in front of where the Cat connects and there is no O2 sensor, nor is there a bung where one might have been ( nor is there evidence of anything being on the pipes )
I really think I need to take this to the dealer.
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Fasstdak
Dodge Dakota
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2/09/2007
23:45:17
| RE: map sensor question
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Yeah...something doesn't make sense here. The front O2 sensor monitors fuel delivery and the rear monitors cat efficiency (along with long term fuel trim input). The rear O2 isn't really that important to fuel delivery, but the front is required. If it's not there, the PCM uses calculated values which could cause some really strange performance issues when not in open-loop (or wide open throttle) mode.
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Mike Stager
Dodge Dakota
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2/11/2007
00:54:47
| RE: map sensor question
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See, that's the strange thing. When I bought the truck, the Check engine light was always on. But I've had good performance and mileage ( 18mpg ). I cut off the Cat ( due to it rattling ) and my mileage went down, but performance stayed the same. I replace the O2 sensor and have the computer reset, suddenly I'm getting horrible mileage ( 10 ) and a complete loss of power once the system goes into open loop ( I can only assume it's going into open loop because it happens after driving the truck over 30mph for a few feet. Once I've driven it for a while, it'll run just okay. As soon as I start from a stop though, it'll stumble like the injectors are being shut off.
What I'd like to know is what the hell happened between replacing the O2 sensor ( I drove it for a while before I had the computer reset ) and having the computer reset. I even tried driving the truck with the O2 sensor unplugged from the harness thinking the new one might be throwing off the ECM. Didn't change the behavior of the truck.
Also, I see no where in the engine wiring harness where there would be a connector for another O2 sensor, and the fact that the Check Engine light has gone off with the truck running worse than ever has REALLY got me scratching my head. You'd think that the check engine light finally going off would mean that I'm running within spec. Obviously not if I'm getting crap for mileage and horrible performance.
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Fasstdak
Dodge Dakota
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2/11/2007
02:25:48
| RE: map sensor question
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Open-Loop operation is within the first 30-120 seconds of startup and when at WOT...not normal cruising. The O2's are (almost) ignored in open loop operation.
I'm still wondering where your forward O2 sensor went.
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Mike Stager
Dodge Dakota
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2/11/2007
11:48:09
| RE: map sensor question
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Message:
Where I say Open loop, I mean closed loop. For whatever reason I was having a brain fart on that.
Either way...yes, I'd like to know why I don't have a second O2 sensor when everyone says I should have one.
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Mike Stager
Dodge Dakota
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2/14/2007
00:10:25
|  RE: map sensor question
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Message:
Okay, you can all color me stupid. I found the Upstream O2 sensor. Don't know how I kept missing it, but I did. I was expecting to find the wires off the frame, not off the area by the transmission tailshaft to a sensor mounted upright. Found it tonight after seeing a schematic and looking for it with a flashlight in the dark. Apparently my physical search was worthless and looking in daylight must have given me the wrong light to see the thing in. Guess that's what I get for assuming I was right without THOROUGHLY looking for it.
Oh well. At least now I've got something to focus on.
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Fasstdak
Dodge Dakota
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2/18/2007
00:37:17
| RE: map sensor question
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Ok...got the spreadsheet updated with some real-world values for the PCM calculations...
http://www.dodgetrucks.org/fasstdak/Automotive_Calculations.xls (Copy/Paste the entire line into the browser)
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Mike Stager
Dodge Dakota
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2/18/2007
10:44:28
| RE: map sensor question
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Message:
that comes up all garbled in Microsoft Excel as an unrecognized format.
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Fasstdak
Dodge Dakota
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2/18/2007
14:21:43
| RE: map sensor question
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Wierd...it's corrupted. I'll fix it and re-upload it.
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Mike Stager
Dodge Dakota
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2/18/2007
18:14:49
| RE: map sensor question
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good to go now.
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Fasstdak
Dodge Dakota
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2/18/2007
18:22:20
| RE: map sensor question
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Message:
Figured it out - it was Excel 2007 format (XML)...oops...had renamed the file to .xls and didn't realize what format it was in. (@#$! Microsoft).
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