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Bad miss under acceleration

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Old Dec 17, 2015 | 01:06 AM
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Bad miss under acceleration
i have a 97 f150 with 4.2 4x4 auto. i have a bad miss under acceleration. if i ease on the gas no problems. stomp it and it chugs and pops back thru airbox til it gets to 2500 rpm then clears up. if i shift it manually and keep rpms up its fine till it gets below 2500. i have replaced spark plugs, plug wires, fuel filter, upper and lower intake gaskets, cleaned injectors, new air filter and cleaned o2 and mas sensors. had vacuum system checked and was told all good. if anyone has any ideas i would greatly appreciate the help
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Old Dec 17, 2015 | 05:13 PM
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and no code light ?
 
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Old Dec 17, 2015 | 06:34 PM
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Coil Pack?
 
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Old Dec 17, 2015 | 06:35 PM
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Coil Pack? ? ?
 
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Old Dec 17, 2015 | 06:35 PM
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Coil Pack..............?
 
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Old Dec 17, 2015 | 06:36 PM
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Maybe the Coil Pack?
 
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Old Dec 17, 2015 | 06:37 PM
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Originally Posted by roundheadlightsonly
i have replaced spark plugs, plug wires, fuel filter, upper and lower intake gaskets, cleaned injectors, new air filter and cleaned o2 and mas sensors. had vacuum system checked and was told all good. if anyone has any ideas i would greatly appreciate the help
..

Coil Pack?


Sorry about that. My computer started to stutter.
 
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Old Dec 18, 2015 | 10:03 AM
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coil pack replaced also
 
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Old Dec 18, 2015 | 10:11 AM
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also checked vacuum and electrical connections to I.R.C.M. cleaned all carbon deposit from intakes . just pulled plugs back out all look fine.
 
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Old Dec 18, 2015 | 03:54 PM
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Fuel pump also replaced?


Try taping a fuel pressure gauge to the wind shield and go for a test drive.
 
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Old Dec 19, 2015 | 03:19 AM
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will try fuel gauge. I think it should idle@65p.s.i. and 70 p.s.I. under load . where is the best place to tap in.. fuel rail connector?
 
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Old Dec 20, 2015 | 02:58 AM
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can anyone help me with proper fuel pressures? idle and under load. 97 4.2 auto 4x4
 
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Old Dec 20, 2015 | 04:22 PM
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Running - 28-45 psi.
KOEO - 35-45 psi.
per shop manual.
 
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