ok so i have had a cylinder 3 misfire since i got the truck here is a list of what ive done to try and remedy the issue but to no avail...

replaced the complete head twice
new cap, rotor, spark plug wires and spark plugs
had the fuel injectors cleaned and tested
leakdown test *passed*
compression test *passed*
checked to make sure i was getting spark definitly felt that one so *passed*

now im at a loss i have no idea what to check next the only error code i have is the P0303.

Thanks,
Tony

forgot to add its a 2001 1500 5.2l 2wd

 

Have you pulled the plug to see how it looks? Blown plenum fouls out plugs which leads to misfires, but usually #8.

 

Check the fuel pump. If it is not working right, it will cause misfires in the engine cause it wont be able to supply enough fuel...

 

The injectors may have been tested, but what about inspecting the injector connector and harness for damage?

 

If the harness was bad, it should be throwing both misfire codes and P020X codes, where X is the cylinder that the injector was malfunctioning on (there could be more than one). Not saying it couldnt be a bad harness and not throwing codes, but more than likely it would be... BTW watch out! If your harness goes bad, it could blow your PCM!! Just happened to me...

 

AND hanging either an oscilloscope or a noid light on there to verify that the pulses are present.

 

Just need a 12-volt test probe... Unplug ONE injector at a time AT IDLE speed, then hook the probe into the injector pigtail and watch it flash...

One other thing, with the engine off, unplug the injector and take a ohm meter and test the resistance of the injectors... I think it should be around 14 ohms... Someone correct me if I am wrong!

 

The injectors ohms are all within 4% is what the guy told me and the harness is good and supplying voltage to each injector.

If it was fuel pump the misfire would be on differant cylinders.

I went to do my emissions testing today and when I first got there it said not ready to test so I took it on the freeway for like 20miles and then took it back and it passed.

So it passed and isn't giving any error codes so maybe the injector service fixed it. However it still feels like it has a rough idle...

 

Rough idle? Hmm... Check your fuel pressure JUST TO BE SURE... It could cause you rough idle!!

 

Rough idle...check IAC next.