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7 miles to the gallon and burning rich
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devesvws
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PostPosted: Sat Feb 01, 2014 6:48 pm    Post subject: 7 miles to the gallon and burning rich Reply with quote

I got 106 miles from fill up to it running out of gas last time I drove it?? what the heck?? its been a few weeks since I last drove it and ran well last time. unplugging the green wire from the Oxygen sensor makes it run normal and I did swap the temp sensor with a known good one but still no good. so I replaced the less than a year old Oxygen sensor with a used one but still no go, as soon as the green wire is plugged back in it starts running rich again.. if it is the Oxygen sensor why would it go bad so soon??? oh btw I have the 80 degree Thermostat not the 87
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hdenter
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PostPosted: Sat Feb 01, 2014 8:21 pm    Post subject: Reply with quote

Inspect the wire for the O2 sensor. If there is even a slight problem with it, it throws off the signal. There is an outer grounded sheath that must not contact tne inner signal wire.

Hans
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DirtyBlueVan
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PostPosted: Sat Feb 01, 2014 8:54 pm    Post subject: Reply with quote

Check for exhaust leaks before the O2 sensor.

It can suck air through the leak creating a false lean o2 reading.
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plummerdesign
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PostPosted: Sat Feb 01, 2014 10:27 pm    Post subject: Reply with quote

Have you done a compression test?
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ute
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PostPosted: Sat Feb 01, 2014 10:58 pm    Post subject: Reply with quote

Manual fuel pressure regulator...mine was bad and I was getting 7mpg.
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devesvws
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PostPosted: Sun Feb 02, 2014 5:02 am    Post subject: Reply with quote

ute wrote:
Manual fuel pressure regulator...mine was bad and I was getting 7mpg.
if I unplug the green wire from the O2 sensor and it runs great, how does that affect the ''Manual fuel pressure regulator'' ? clearly its electrical in nature, but I guess it could be mechanical.... btw everything is in order and I'm always on top of anything that it might be in need of, just sayin.....
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morymob
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PostPosted: Sun Feb 02, 2014 5:42 am    Post subject: Reply with quote

If it runs close to norm with oxy wire unplugged u don't have a fuel press problem. DO as already mentioned, check oxy wire at conn plug-ecu side, outer shield will fray and a strand(s) will touch center wire grounding it out, WILL run rich. Meter from shield to center, NO SHORT reading, some hi reading thru ecu internals normal. Very common problem.
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devesvws
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PostPosted: Sun Feb 02, 2014 11:22 am    Post subject: Reply with quote

I just drove it to the store about 18 miles away and it started to stumble and surge just a little on the way, but coming home it ran fine. why I never think to check the ''oxy wire at conn plug-ecu side'' smh
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rsbones
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PostPosted: Sun Feb 02, 2014 5:55 pm    Post subject: Reply with quote

Fwiw, I thought I got really bad gas mileage for a couple of a tanks until one day I looked down and the odometer wasn't moving. Apparently it had started working only intermittently. (Now it doesn't work at all). So make sure it's working before you use it for calculating mileage!
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devesvws
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PostPosted: Sun Feb 09, 2014 7:31 am    Post subject: Reply with quote

*update* so for the most part it's running ok with the green OX sender wire unplugged and back to 15 mpg over all, btw I have checked the speedo many times and it is about as accurate as a vanagon speedo can get. looking around everything looks in place and wires look ok. I think I will do a major tune-up with a new OX sender and new temp sensors, it has run flawless since I replaced the old AFM with a reman AFM and reman fuel injectors, that was about 8k ago. when I first got it going after rebuilding the motor it would start at the first click of the key now it takes about 4-5 turnovers for it to start. I also have some sort of issue with the battery going dead (new battery) it sat a day and a half this last time it went completely dead in 4 days before that, so I'm wondering if there might be a link to it running rich??? I did replace the alt about 4 months ago....
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funagon
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PostPosted: Sun Feb 09, 2014 8:48 am    Post subject: Reply with quote

you still haven't tried what morymob and hdenter suggested? There's your answer. You have to make sure that the green wire to the OXS is working properly.
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devesvws
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PostPosted: Sun Feb 09, 2014 9:11 am    Post subject: Reply with quote

I replaced the OX sender with a used one that was good, even though the one I removed was less than a year old. i checked and traced the wires for any kind of broken wires or chafed wires from the plug going into the main wire harness and cleaned the whole harness the best I could, like I said all looks normal. am I missing the point or something?? I assume it is one or both the OX and temp sensors, plus doing a major tune up cant hurt...
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PostPosted: Sun Feb 09, 2014 7:13 pm    Post subject: Reply with quote

The worst fuel mileage I ever experienced was caused by low coolant! You can doubt it if you want but this was during a 12 hr drive and I had another vehicle traveling with me that fueled on the same schedule as I did. Eventually i realized I was fueling way before they needed to. And once I realized my coolant was low and fixed that the fuel consumption went back up immediately!
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ute
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PostPosted: Sun Feb 09, 2014 9:40 pm    Post subject: Reply with quote

I went down same path...and it turns out my O2 sensor was bad along with the silver regulator. I hear they rarely go bad, but mine did while half way through a cross country drive.

It is a cheap part and help keep fuel rail pressure where it needs to be. It ran REALLY rich for me...hence me responding.
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Howesight
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PostPosted: Sun Feb 09, 2014 10:32 pm    Post subject: Reply with quote

The answer to your problem has already been given above by prior posters, but I am gonna try agin' ta learn ya.

The wiring between your oxygen sensor and the ECU is compromised. That's the entire problem. The wire is co-axial. The inside wire is the signal wire that sends a very small current signal between 0 volts and 1 volt to terminal 2 at the ECU. The outside wire is a shielding wire. It is supposed to be connected to ground (and not to the signal wire). Its job is to protect the signal wire from electromagnetic interference.

Here's what happens: Either a strand of the coaxial wire or a strand of the signal wire pierces the insulation separating these co-axial wires. This then tells the ECU that there is an excess of oxygen (not so, obviously) and the ECU responds by enriching the fuel mixture to burn up the "excess oxygen".

To test whether this is occurring, you need to check, with a volt/ohm meter, for any continuity between the ground wire and the signal wire. The end point of the coaxial wire is a place where this unintended connection between the coaxial wire and the signal wire can occur, so check that out. The signal from the oxygen sensor is so weak that the slightest connection between the shielding cable and the signal wire can cause the problems you have described.

It is also possible that you signal wire has, somewhere along its path, touched a ground point unrelated to the coaxial wire, and it would be good to check that also.
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Wildthings
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PostPosted: Sun Feb 09, 2014 11:47 pm    Post subject: Reply with quote

Anything thing that creates extra oxygen in the exhaust can cause this problem as can something that causes one cylinder to run at a different mixture than the others. An exhaust leak at the heads, a minor misfire, something restricting air flow to one cylinder, a single injector which doesn't flow correctly.

It does sound similar to ground problem with the wire to the O2 sensor, but it sounds like you have eliminated this as a possibility.
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devesvws
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PostPosted: Sat Mar 08, 2014 9:53 am    Post subject: Reply with quote

Howesight wrote:
The answer to your problem has already been given above by prior posters, but I am gonna try agin' ta learn ya.

The wiring between your oxygen sensor and the ECU is compromised. That's the entire problem. The wire is co-axial. The inside wire is the signal wire that sends a very small current signal between 0 volts and 1 volt to terminal 2 at the ECU. The outside wire is a shielding wire. It is supposed to be connected to ground (and not to the signal wire). Its job is to protect the signal wire from electromagnetic interference.

Here's what happens: Either a strand of the coaxial wire or a strand of the signal wire pierces the insulation separating these co-axial wires. This then tells the ECU that there is an excess of oxygen (not so, obviously) and the ECU responds by enriching the fuel mixture to burn up the "excess oxygen".

To test whether this is occurring, you need to check, with a volt/ohm meter, for any continuity between the ground wire and the signal wire. The end point of the coaxial wire is a place where this unintended connection between the coaxial wire and the signal wire can occur, so check that out. The signal from the oxygen sensor is so weak that the slightest connection between the shielding cable and the signal wire can cause the problems you have described.

It is also possible that you signal wire has, somewhere along its path, touched a ground point unrelated to the coaxial wire, and it would be good to check that also.
is there a replacement oxygen sensor harness on the market? if that is the problem?? I'm just about to buy a few things for it and one thing I'm buying new is a temp sensor connector...
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insyncro
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PostPosted: Sat Mar 08, 2014 11:17 am    Post subject: Reply with quote

I highly recommend reading Tencent's thread on the shielded wire and use a Bosch sensor with the factory pigtail, no splicing.
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devesvws
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PostPosted: Sat Mar 08, 2014 12:10 pm    Post subject: Reply with quote

plummerdesign wrote:
Have you done a compression test?
with plugs removed 2 strokes is 120 on all 4 and 140 avg after 6-10 strokes.
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Ahwahnee
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PostPosted: Sat Mar 08, 2014 12:20 pm    Post subject: Reply with quote

Are you still having the initial problem? The likely problem is simple to diagnose and fix. Mentioned many times already so I'll offer a redux:

Howesight wrote:
...The wiring between your oxygen sensor and the ECU is compromised. That's the entire problem. The wire is co-axial. The inside wire is the signal wire that sends a very small current signal between 0 volts and 1 volt to terminal 2 at the ECU. The outside wire is a shielding wire. It is supposed to be connected to ground (and not to the signal wire). Its job is to protect the signal wire from electromagnetic interference.

Here's what happens: Either a strand of the coaxial wire or a strand of the signal wire pierces the insulation separating these co-axial wires. This then tells the ECU that there is an excess of oxygen (not so, obviously) and the ECU responds by enriching the fuel mixture to burn up the "excess oxygen".

To test whether this is occurring, you need to check, with a volt/ohm meter, for any continuity between the ground wire and the signal wire. The end point of the coaxial wire is a place where this unintended connection between the coaxial wire and the signal wire can occur, so check that out. The signal from the oxygen sensor is so weak that the slightest connection between the shielding cable and the signal wire can cause the problems you have described...


Note - you cannot fix this by replacing your O2 sensor (it's not the problem).

Also note - you said "like I said all looks normal..." -- you cannot diagnose this by looking.

Even one tiny strand loose from the coax and touching the connector on that green wire is enough to fool the system into running stink rich. Only way to find it and to be sure you fixed it is with an ohmmeter as described above.
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