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Discussion Starter #1
Truck started to misfire on 4 & 8 changed spark plugs and had some oil on a few boots. When I put the coils back on with with the new spark plug I flipped them driver side went on the passenger side. Still getting a misfire on 4cyl Any one run into this issue before?
 

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Thought I read on here someone else having the same problem and he replaced the fuel injector which fixed the problem. Cant find that thread right now but I dont think an injector is a whole lotta cash so might be worth a try.
 

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Random misfire is typically only a couple of things.. coil and plug are easy to check first like you did. Run a bottle of fuel injector cleaner and Chevron Techron through with just a 1/4 tank and see if that takes care of it. Before replacing the injector as the next step make sure your fuel pressure is good on the rails.
 

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Random misfire is typically only a couple of things.. coil and plug are easy to check first like you did. Run a bottle of fuel injector cleaner and Chevron Techron through with just a 1/4 tank and see if that takes care of it. Before replacing the injector as the next step make sure your fuel pressure is good on the rails.
how do you check fuel pressure on these 5.7 flex? Also notice my 4LO is flashing aswell.
 

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how do you check fuel pressure on these 5.7 flex? Also notice my 4LO is flashing aswell.
In a nutshell you Tee a mechanical gauge into the fuel line and use the Techstream to command the fuel pump to run for low and high speed.
There are also particular safety procedures to follow so leave it to a professional unless you know what you are doing.
Search the forum for more info, it has been covered many times.

Discharge fuel pressure
T into the fuel rail lines.


Command the fuel pump for high and regular pressure.
Powertrain / Engine and ECT / Active Test / Activate the Fuel Pressure Switching Valve / High.
Measure the fuel pressure.
Standard fuel pressure for High:
370 to 430 kPa (3.77 to 4.38 kgf/cm, 53.7 to 62.4 psi)

Powertrain / Engine and ECT / Active Test / Activate the Fuel Pressure Switching Valve / Low.
Measure the fuel pressure.
Standard fuel pressure for Low:
270 to 330 kPa (2.75 to 3.37 kgf/cm, 39.2 to 47.9 psi)

Check that the fuel pressure remains as specified for 5 minutes after the engine has stopped.
Standard fuel pressure:
147 kPa (1.5 kgf/cm, 21 psi) or more
 

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Discussion Starter #7
In a nutshell you Tee a mechanical gauge into the fuel line and use the Techstream to command the fuel pump to run for low and high speed.
There are also particular safety procedures to follow so leave it to a professional unless you know what you are doing.
Search the forum for more info, it has been covered many times.

Discharge fuel pressure
T into the fuel rail lines.


Command the fuel pump for high and regular pressure.
Powertrain / Engine and ECT / Active Test / Activate the Fuel Pressure Switching Valve / High.
Measure the fuel pressure.
Standard fuel pressure for High:
370 to 430 kPa (3.77 to 4.38 kgf/cm, 53.7 to 62.4 psi)

Powertrain / Engine and ECT / Active Test / Activate the Fuel Pressure Switching Valve / Low.
Measure the fuel pressure.
Standard fuel pressure for Low:
270 to 330 kPa (2.75 to 3.37 kgf/cm, 39.2 to 47.9 psi)

Check that the fuel pressure remains as specified for 5 minutes after the engine has stopped.
Standard fuel pressure:
147 kPa (1.5 kgf/cm, 21 psi) or more
Can leak coil tube gaskets cause a misfire?
 
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