Hey Ya'll, I post over in the LT1 section all the time but have a problem with an Iron LS Truck motor, I have it narrowed down to a leaking fuel injector but want some advice if you have it...

Symptoms:
1) Has set individual cyl missfire code, but forgot what it was
2) Sets random cyl missfire after a while of close loop learning
3) Starts best cold and immediately after shutting off when warm.
4) Starts worst when sitting warm, but interestingly enough when it's cranked with the pedal all the way down (Clear flood mode) it sounds like it fires on one cylinder then stops, if you let it sit for 20 seconds and do the same thing it will fire on the one cylinder again for about 1-3 seconds, repeat process over and over as long as you hold the pedal down (thinking fuel is leaking during this time)
5) Resetting the PCM will make it idle good after it starts like crap and cleans up, but with one intermittent weak cylinder coming in and out.
6) As the PCM learns it's fuel tables the overall idle seems to degrade, becomes less of one single intermittent missfire and turns into just a general rough idle (sounds like a lean idle)
7) Everything off idle is fine, full power, great throttle response, etc.

Been like this for awhile, now it's getting to the point missfire codes are being set.


Im thinking the fuel injector is dripping when full pressure and warm, this is allowing enough fuel to fire the 1 cylinder while cranking at WOT, which runs out eventually and refills pretty quick (10-20 seconds).

Im also thinking the PCM is detecting a rich idle due to the extra fuel and keeps pulling fuel, I dont have software to read the fuel trims, dont even have a way to pull codes, have to go to Autozone.

Waiting for the next individual cyl missfire to pop up and investigate that injector.


Any idea's? Thanks for reading all that!

 

Unbolt the rails from the intake. Pull the rails and injectors just out of the intake and turn the ignition switch to the run position. Watch the suspect injector. That should answer your question in 10 minutes.

 

If you have a fuel pressure gauge, hook it up to the rail, key it up for pressure, then watch. A good fuel system will hold the pressure.

-Geoff