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Fuel Pump Failing?

This is a discussion on Fuel Pump Failing? within the General Help forums, part of the LSx Technical Help Section category; well they called they are 98% sure its the pre cat 02s causing a bad reading screwing the computer up ...

  1. #21
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    well
    they called
    they are 98% sure its the pre cat 02s causing a bad reading screwing the computer up
    they are pretty sure replacing them will fix the problem...

  2. #22
    Moderator Cutlass's Avatar
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    With bad precat O2s it should run ok on a cold start (open loop) and then after a little bit of warming up (closed loop), it should start to run like crap. If thats not the case, then I'd be suspicious of their diagnosis.

  3. #23
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    their words not mine
    it used to get worse when warm, now like i said its all the time it runs like crap
    they said that cycl 2 was all over the place, the replaced the plug, wire, coil and injector and still was acting up
    he then checked the O2 reading and again they were all over the place so he says its the 02s

  4. #24
    Moderator Cutlass's Avatar
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    ok well if its isolated to cylinder #2, then its not an O2 sensor problem. If its not the plug, plug wire, coil, or the injector, then it could be the wiring/computer problem for the coil or injector. Both are very easy for a technician to test. A spark test confirms the ignition system is ok. An injector drive test confirms the computer is firing off the injector. If it has both injector drive and spark, then the next thing to check for is mechanical problems like low/no compression on cylinder number 2. Causes could be broken/stuck rings, bent valve, bent rod, hole in piston, or other valve train related problems. Easily checked with a compression and cylinder leak down test.
    So question them in this order...Does it have spark? Does it have injector drive? Did you do a compression and/or cylinder leak down test?

  5. #25
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    did compression
    it checked out
    hes apparently their head tech (which i trust since my uncle is his boss)
    he said he went over everything pretty well and this is his best guess as to what it could be...

  6. #26
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    is there an update? any progress pin-pointing your problem?

  7. #27
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    Quote Originally Posted by Camaro98Z/28 View Post
    well
    they called
    they are 98% sure its the pre cat 02s causing a bad reading screwing the computer up
    they are pretty sure replacing them will fix the problem...
    Does the car run poorly on a COLD start??

    If so, its NOT the O2 sensors. Whenever you start the car cold, its in open loop, meaning the readings from the O2 sensors aren't used by the ECU. The O2 sensors are nothing more than feedback devices for the ECU to determine fuel trims.

    The technician probably thinks its the O2 sensors because the readings on the sensors are going to be way off due to the engine running poorly when warm. It its got a random/cylinder misfire and its getting fuel, the exhaust is going to be pig rich. Meaning the O2 voltages are going to hover in the upper end of the spectrum, which he may be interpreting as bad O2 sensors.

    I'd be weary of trusting that dealer to repair your car, sounds like they aren't very knowledgeable.

  8. #28
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  9. #29
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    Quote Originally Posted by Camaro98Z/28 View Post
    oops, i read that but my brain didnt click it to this!

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