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Odd misfire from 5.2

679 views 1 reply 2 participants last post by  OSHA Violations 
#1 ·
Hello. I have a 1999 Dodge Dakota SLT 4x4 318 with a nv3500 5 speed manual. I am here because i have a odd issue with this truck. The truck has a single misfire when driving and heat soaked or hot. Maybe after 30 minutes of driving or 30 miles it will start to have a single misfire or a dead flat shut off for about a second. And it does this randomly many times until your done driving. Its like a quick OFF and back On. It doesnt feel like a single cylinder miss it feels as a whole ignition shut off. Sometimes if your in the gas when happening it will have a small backfire. So im assuming its getting fuel. Ive checked the following:
Used coil from known good engine.
New champion plugs
New wires, cap and rotor
New mopar crank sensor
New mopar cam sensor
New ASD relay
Cleaned PCM grounds.
Fuel trims look good. Left oxygen sensor reads around 0.4 volts right reads 0.1 during normal driving on highway.
Ran a LED light on the power side of coil/injectors and light did NOT go out when truck acted up.
Ran a led on the pcm negative wire to ASD relay. LED didnt go out when truck acted up.

Only drivability issue with truck is when coasting it will idle surge from 700 to 1200 when moving with clutch pushed in. Never idle surges any other time and has great idle. Cold idles high and levels out to 700 normally.
My next suspect is faulty PCM.
Any ideas or help would be greatly appriciated! Thanks
 
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#2 ·
Check your vacuum, these engines have a pan on the bottom of the intake slight enough leak that you are not losing oil to notice but enough to run lean. Leds are good for a dead fault but you need to hook up a digital oscilloscope to get split second signal failures. No codes? No freeze frame? I can only shoot ideas in the dark.
 
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