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poor running '85

 
Old 07-20-2012, 02:23 PM
  #46  
byrdman454
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rexpontius,
What did the failed pin look like? I did look at the on the caps and the pin was still there and the sping loaded action of them still worked. I pushed them in and they popped back out just like they should to maintain contact.
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Old 07-20-2012, 02:24 PM
  #47  
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I will unplug the o2 sensor next and try it.

I started to pull the gas out of the tank just in case my nephew accidentally put diesel in the tank or got a bad batch from the station. He is just a teenager...you never know.
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Old 07-20-2012, 02:44 PM
  #48  
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My pin was snapped, so there was only a very short piece sticking out (1mm) barely making contact to the rotor.
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Old 07-20-2012, 03:03 PM
  #49  
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Unplugged the o2 sensor and the car runs the exact same. I am assuming the sensor is out even though I changed it just over a year ago. Can it be anything else like wiring versus just the sensor?

Had my nephew drive back by the gas station he used yesterday and teh pump he used did not have a diesel option, so I dont think it is the gas.

What o2 sensor do I need to buy? Universal or the one with the correct plug? Is Rog the cheapest?
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Old 07-20-2012, 03:12 PM
  #50  
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If unplugged and runs the same, then the O2 is probably OK.

Also, the O2 sensor should not affect starting.
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Old 07-20-2012, 03:19 PM
  #51  
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Ken,
If I unplugged it and it ran the same, don't you think the sensor is bad? I would think if it ran worse, then the sensor would be ok.

It still requires some throttle to get it going, but after it is running for a short bit it idles steady and on its own at the correct RPM. The car shakes a bit at idle, but you can really tell it is not happy when applying throttle.
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Old 07-20-2012, 03:30 PM
  #52  
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Ken,
What issues would the car have if I put 87 octane in it with your 92 octane s300 chips?
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Old 07-20-2012, 03:33 PM
  #53  
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What about the MAF?
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Old 07-20-2012, 03:38 PM
  #54  
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He tried that already, see his initial post....
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Old 07-20-2012, 04:03 PM
  #55  
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Missed it. Sorry. I now want to say check the grounds at the back of the engine.
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Old 07-20-2012, 04:55 PM
  #56  
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Originally Posted by byrdman454 View Post
What issues would the car have if I put 87 octane in it with your 92 octane s300 chips?
Nothing really noticeable, at part throttle. It may ping around 3500 in cruise, and may knock(!) around 2700, and over 5000 rpm at heavy load.
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Old 07-20-2012, 06:30 PM
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Just making sure the 87 octane wouldnt be causing this rough running problem.

Ken, why do you think that since the car ran the same with the o2 sensor plugged and unplugged means that the sensor is ok. Just trying to understand the reason for the test. If it was any other sensor, I would say this is proof the sensor is not working.
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Old 07-20-2012, 07:56 PM
  #58  
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Unplugging the o2 sensor causes the ECU to go "open loop" and default to an internal set of parameters instead of relying on the input from the o2 sensor to tell it how to adjust mix. If the o2 sensor was faulty it could be causing the ecu to do all sorts of goofy things based on bad input signal. Unplugging the sensor makes the ECU ignore that input and revert to the stored settings. This would eliminate the 02 sensor as an erroneous input.

Mike
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Old 07-21-2012, 12:14 AM
  #59  
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I agree that would indicate they are both working. Also tells me that it is not likely a spark issue at all. You may have an issue on the fuel side. If you have a noid you can test each injector. You may find one bank is missing. Doesn't the chip kit come with two chips? Maybe one is bad? Never tried unplugging computers one at a time but in your situation I would be willing to give it a go. Certainly won't tear anything up. See if you can isolate it to a computer.

Make sure the vacuum to the computer got plugged in. a vacuum leak can cause rough running until the car warms. Also the car would run poor in WOT if this was not connected. IF you have a vacuum gauge you should have around -2 BAR (-40ish PSI)
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Old 07-21-2012, 04:39 AM
  #60  
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This is all curious.

To test the o2 sensor connect a VOM and run the engine. The o2 sensor should generate between a half a volt to amost a full volt. As it gets to the high side the voltage will peak and then fall off to the low end of the range before moving up again. The engine should change a little in idle accompaning the change in voltage. If the voltage cannot climb above perhaps 0.6 volts then the o2 sensor is shot. A bad o2 sensor will raise the NOX but should not create a noticable change in how the car runs.

It is curious the engine dies when you pull the apmlifer. It should still idle. The fact that it dies on both sides suggests the coils are good along with the rest of the ignition. It happened suddenly so somthing could have failed, but if a cap went bad then one side should run stronger than the other. but that is not happening so I would eliminate the possibility of ignition.

What else makes a car run - air and fuel. You need enough of both. I would consider it occurring on a low gas tank coincidental since you did a tank service recently. Gas with ethanol does not have the water problems of the past so things should still be pretty clean.

That brings things back to a blocked input, a block exhaust or somthing messing with the fuel pressure.

You can just crack the cat at the headers and eliminate the back pressure issue. You did not say if you put on a pressure gauge.

I hopes this helps. Other areas are sensors that could limit enough fuel.
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