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    Thread: Please Help! Stalling, violent idle, no acceleration

    1. #11
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      I checked for vac leaks and couldn't find any but I will definitely replace the map sensor and go from there! Thank you and if you think of anything else, please let me know. I am very desperate at this point.



    2. #12
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      One other thing, I have an obd2 scanner with liveview and looking at the map data during (rough) idle, it's reading 56kpa. Is that off what you'd expect?

    3. #13
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      Quote Originally Posted by Chrisj4269 View Post
      One other thing, I have an obd2 scanner with liveview and looking at the map data during (rough) idle, it's reading 56kpa. Is that off what you'd expect?
      I had seen that and, assuming an idle of 600-700 RPM, that 56 is probably near the upper limit of being ok. It's always better to get a number of readings at different RPMs, but unfortunately trying to figure out if that sensor is ok while on the vehicle is not an exact science in any case. The MAP sensor would need to be removed from the vehicle and bench tested with a pump, in order to determine if it's good or not.

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      Ok thank you. I'll get the map sensor ordered. Anything else I should go ahead and get ordered while im at it?

    5. #15
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      Quote Originally Posted by Chrisj4269 View Post
      ... Anything else I should go ahead and get ordered while im at it?
      Yes, the MAP sensor vacuum tube - they get brittle and crack as they get older.

    6. #16
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      I have replaced the MAP sensor with genuine GM part and also the vac line. No change... Please help. Any other suggestions???

    7. #17
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      Did that improvement in performance a few days ago happen after you cleaned the throttle body, or one of the other things you did?

    8. #18
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      It happened after replacing plug wires and ignition coil but quickly went back to running very poorly. I exchanged the coil pack at the auto store after that happened just to insure that the coil wasn't the issue and I got one that only lasted about 20 minutes for some reason

    9. #19
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      Quote Originally Posted by Chrisj4269 View Post
      It happened after replacing plug wires and ignition coil but quickly went back to running very poorly....
      That's actually a fairly good clue, and provides a direction for some additional testing that you can try. First start it up with the engine deco cover off, at night with as little light as possible (completely dark is best). Take a look while it's idling, to see if you see any arcing. If nothing shows up, then spray a fine water mist onto the engine to see if that results in a light show.

      If you don't find any arcing, then check the spark of each plug individually, and compare them to each other. An HEI spark tester is best, but a regular inline spark tester can diagnose problems as well. You can even use the redneck method of simply grounding the plug to the block and watching the actual spark. It's best to first run the fuel dry by pulling the fuel pump relay and letting it stall out, because it's easier to read the spark when it's less frequent. You'll probably want to have a helper crank the engine, while you watch the spark from the front of the bay.

    10. #20
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      I had a mechanic look at it today and he suggested it may be the pcm. He was watching the data and load was showing 100% at idle, throttle at 50%+ and intake air temp of -40c (brand new sensor and verified with a new one). What are your thoughts on that?





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