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Car stumbling after 4g

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Old Mar 11, 2006 | 07:35 PM
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Default Car stumbling after 4g

Any i deas of what this could be?
Stock 99 Z28 with a whisper lid, If i launch the car off a foot brake, at about four grand the engine is still pullin RPM's but the car falls on its face...The car will rev to 6 grand all day but after 4 grand the front end drops and goes nowhere till it hits second and there on after... But it is inconsistent. Doent always do it sometimes it feels strong..
THING IVE ALREADY REPLACED
-Brand new GM performance parts 4L560E (warranty)
-Fuel filter
-fuel pump
-brand new converter (warranty)
Also have had the computer scanned several times, and nothin comes up
ANY IDEA"S
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Old Mar 11, 2006 | 11:40 PM
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spark plugs/plug wires. Possibly a coil. Could be a sensor as well. Dirty MAF maybe. I would try plugs/wires first. Good luck
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Old Mar 12, 2006 | 12:40 AM
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Thanx man this things turnin into a maintanace freak....any other opinions
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Old Mar 12, 2006 | 02:46 AM
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i had the exact same thing happen to me and it was a loose spark plug wire
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Old Mar 12, 2006 | 05:01 AM
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Injectors might be running at their max duty cycle. Hope it isnt that. you don't want to lean your **** out!
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Old Mar 12, 2006 | 01:23 PM
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The thing is bone stock with a lid so thats out of the q's id think
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Old Mar 12, 2006 | 02:21 PM
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Check your knock retard by logging some runs on autotap to see. I have had the same problem and thought it was a transmission problem and it turned out to be a broken knock sensor wire.
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Old Mar 12, 2006 | 05:22 PM
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Nt to sound like a meatball but whats an autotap
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Old Mar 12, 2006 | 07:54 PM
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Throttle Position Sensor.
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Old Mar 12, 2006 | 08:34 PM
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any reason to believe it is not related to the fuel pump? The faster your engine is running the more fuel it is calling for.
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Old Mar 12, 2006 | 08:35 PM
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Brand new fuel pump. I only have about 58 miles on the new trans coverter and fuel pump
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Old Mar 13, 2006 | 11:10 AM
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Ttt...
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Old Mar 13, 2006 | 12:23 PM
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edit-didnt read the tranny replacement, id get a friend with either autotap or hptuners see what codes are being run, and then id take it to the dealer and see whats up, good luck
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Old Mar 13, 2006 | 06:29 PM
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Ttt!!!
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Old Mar 13, 2006 | 07:02 PM
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mine was doing the same thing, replaced spark plugs and wires, and it went away.
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Old Mar 14, 2006 | 09:27 AM
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Im gonna do that after work today and let you guys know what happened
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Old Mar 14, 2006 | 04:04 PM
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Mine did this and it was the Throttle Position Sensor (TPS). If you have an Ohm meter handy, take it out and check resistance across it. My car would climb to a certain RPM and choke out and not climb anymore, but it was fine below a certain RPM. It was because one of the resistor strips read infinity and could not transmit a signal to the throttle-body actuator to open the blade any further. So it would stumble and gain speed but only very slowly, because air was being allowed in. Checked everything else and ran diagnostics and it was never discovered--apparently the ECM doesn't see a problem if there is some airflow. Before that I changed the plugs and wires and that didn't solve ****.

If it's only happening sometimes, the TPS might be on the fritz and is on its way out.
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Old Mar 15, 2006 | 02:18 PM
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I was also thinkin that after i talked to one of my techs at work so im gonna check that on saturday when i have time.I also aquired a new granitelli maf so im gonna throw that on. Its free why not. ITS AMAZING WHAT YOU FIND IN THE BACK OF A DEALER CAR
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Old Mar 20, 2006 | 10:22 PM
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changed then maf 2 days of drivin no stumblin
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