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7.4 missfire help

ScottL5385

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ScottL5385 Enthusiast

ScottL5385

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I have a 2000 k3500 dump with a 7.4L Auto

Has not been running properly since i purchased.
When first bought, it would begin to accelerate, then hesitate. If throttle was pushed harder it would take off and run great.

Upon purchase the egr was blocked and was showing a maf code.
Unblocked egr, cleared code and came back. Replaced egr, and code went away. Installed a new maf and upon installing maf i noticed a bad connection with the wiring harness to the maf and spliced in a replacement, code went away. also did pcv valve, iac, throttle position sensor.

Truck was running better but still had the hesitation. I replaced the pcv valve, iac, tps and still didnt work correctly. After checking many connectors i found the map sensor was cracked at the intake and only held on by the tab.
Replaced map sensor, and the truck now was running good.

FF a few uses, and now the truck is hesitating/missfiring multiple cyl, mostly 1 but also few on, 2, 3, and 8 again but only after going open loop at 180 and hard to start after warm.

Read many places saying check fuel pressure, found that it dropped to around 40. replaced fuel pressure regulator and injectors. now pressure is 58 initially while cycling key on and off 52 after key is in the on or off position.
This solved my hot start issue.

Next I replaced the complete distributor, wires, and plugs did not help.

Still having trouble with the hesitation it is around 1500 rpm and only while going pretty slow forward or reverse in the yard/driveway

truck has a fairly new exhaust also including highflow cats from previous owner and magnaflow muffler that i did to replace glasspacks.

Can anyone give a direction to look

 

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