First Time LSX swap review

Discussion in 'High Tech Retrofits' started by jb451, Aug 5, 2014.

  1. jb451

    jb451 Veteran Member

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    58psi at the rail with key on, same at idle. I'll wait until tomorrow morning and try again, it will usually act up for a second or two on a cold start. Yeah, lots Tom, lots and lots of fun.lol

    CL, thanks man, didn't think about the MAF, ill clean it tomorrow.
     
  2. mrvedit

    mrvedit Veteran Member

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    A quick MAF test is to simply disconnect it. Unless you are sure your PCM is tuned for Speed Density with your engine combo and all sensors are working, I don't recommend WOT without the MAF as things may go dangerously lean. IIRC when you disconnect the MAF the PCM also stays in open-loop.

    Do you have a tuner like HP Tuners or EFI Live?
     
  3. sbca96

    sbca96 Veteran Member

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    I had a no start, backfire sputter issue with the 1995 Impala SS LT1, I thought it
    was the opti, though opti test showed it was not bad. Went through the trouble
    of changing it out (dumb dumb dumb) and it didnt solve the problem (duh). When
    I had the WP off and MAF disconnected the car ran, hooked everything up and it
    wouldnt start. Tried a known good MAF and it started right up. Turned out that
    the MAF was bad ... BUT .. it should have ran with the bad MAF!! It should have
    gone to MAP and ran in open loop, but it didnt. I still dont know why. Runs fine
    now and I have a lifetime warranty opti ... and an extra opti.

    Point is ... the little things can ruin your day.

    http://www.nastyz28.com/forum/showthread.php?t=247904

    I reread what happened and I had to disconnect the temp sensor on the WP also
    for it to actually run, so MAF and temp sensor.

    Tom
     
    Last edited: Nov 2, 2014
  4. jb451

    jb451 Veteran Member

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    Is there something i am looking for when i unplug the MAF? I did that yesterday and the idle changed some, but i did not drive the car around. No, i just had LT1Swap.com program the PCM, past that i haven't touched it.


    Just thinking out loud here, but would a decrease in engine temperature cause poor idle/drivability? I forgot to mention, my engine normally operates between 180* and 190*, and yesterday it was down around 165*-175* even around town, due to it being in the low 40's and 50's yesterday and the day before. Coming from the 80's down to high 30's low 40's in the span of overnight shouldn't be an issue for the PCM to compensate….right?
     
  5. mrvedit

    mrvedit Veteran Member

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    What you are "looking for" is whether unplugging the MAF makes the car run better.
    Temperature wise, my car is doing exactly the same thing - running 170F instead of 190F. It should make no difference.
    However, if your PCM is reading e.g. 140F from your IAT, but it is 40F out (denser air), you will run very lean.

    This is all easily figured out by hooking up a scanner to the car. Otherwise we are all just guessing based on your observations.
     
  6. jb451

    jb451 Veteran Member

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    Hm, well i guess i will have to find someone who has one then, i don't have access to a scanner that show realtime data, just codes.
     
  7. jb451

    jb451 Veteran Member

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    Forgot to update a week ago, but I'm 99% sure I solved the issue. My engine came out of a hydroboost equipped truck, so my vacuum port on the back was capped. Well I cobbled together a nipple using the old cap. Guess it came loose or something, causing a leak every so often. Replaced it with a nipple from a non hydroboost truck and no issues or codes since. Thanks fellas.
     
  8. sbca96

    sbca96 Veteran Member

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    Usually something simple at this point. Nice catch!

    Tom
     
  9. jb451

    jb451 Veteran Member

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    Injector circuit issue

    Copied from my thread over at LS1Tech-


    LQ4 started originally by throwing a lean code for both cylinder banks as well as a nasty misfire and backfiring, found out 1 3 6 8 are dead by unhooking spark plug wiring and injector pigtails and listening to the idle. also suspected a vacuum leak, but i couldn't find any. It does not change when you unhook those wires, but the other 4 cylinders will go dead if you unplug them. Noid light shows a pulse, all injectors ohm out between 12.6 and 13.1 ohms. Trouble code p0200 for an injector circuit malfunction, the lean codes have went away. Brand new harness too, double checked injector pins… Pulled injectors and soaked them overnight in injector cleaner, and pulsed them to make sure they actuate (which they do). Had a friend at work hook it up to a live data scanner, no misfire counters were being recorded. I'm stumped, and would appreciate any ideas on where to head/look next. The car did have the lean codes before i put the harness in, but drove/idled fine with no misfiring, just an occasional backfire.

    ----------------

    Bump…. took a stethoscope to each injector, they are all firing (well they are clicking at least.)… Not sure if its at the right time, but they are all firing. Hooked an inline spark tester up, spark on each cylinder, dunno if its good/enough spark or not though.
     
  10. 5.73LSXCamaro

    5.73LSXCamaro New Member

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    Man, i really like your motor trans swap. Looks like it really turned out great. I'm in the middle of my LSX swap right now and your page has a lot of good info. Thanks.
     

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