So since it finally got humid here in AZ, i started driving the limo again. over the winter, i noticed a little knock after going on a couple trips to the dunes but wasnt anything that warranted me diving deeper into it. Well this past week ive really taken notice to it.
here is what she does. when cold, it wont knock. sounds happy as can be when cold. soon as she warms up it starts knocking on one cylinder (#5 to be exact). this knock sounds like a fuel knock when you unplug the FPR and give it full rail. its not quite by any means as i can hear it in the cab easily. it would only knock at idle in gear over the winter, then it started to do it in park begining of last week, now im fairly sure i hear it a little cruising the highway. No smoke, no haze, no bad MPG, not making oil, no puffs of smoke out the oil fill, no blown out dipstick from a broke piston. fuel return isnt all that much even taking the main return line off. i was actually surprised at that. its just a little trickle.
at first i thought it might be tuning as running the stock tune would quite it down so i messed with the tuning a bunch, increasing rail then decreasing (above and below stock), adding or subrating timing (above and below stock), and attempting to see if messing with commanded idle mm3 would do anything. So what i thought fixed it was lowering everything as it quiet it all down and it was good for a day, then it came back just as loud as before. If you shut cyl 5 off, knock is completely gone and she sounds great besides the miss. So i tried some injector clean thinking maybe they are a little gummy after 25k. made absolutely 0 difference. balance rates are no higher than -+2.0 accept for cyl 5 which is positive 6.
at this point, im thinking the copper seal is no longer sealing in the cup for the injector or the injector is bad its self. the positive number makes me think compression is a little lower in that cyl from it not sealing or maybe a weak coil on the injector.
anyone else have any ideas to double check? ive tried to do most of the diag before posting. valve cover comes off tonight. least its on the easy side
here is what she does. when cold, it wont knock. sounds happy as can be when cold. soon as she warms up it starts knocking on one cylinder (#5 to be exact). this knock sounds like a fuel knock when you unplug the FPR and give it full rail. its not quite by any means as i can hear it in the cab easily. it would only knock at idle in gear over the winter, then it started to do it in park begining of last week, now im fairly sure i hear it a little cruising the highway. No smoke, no haze, no bad MPG, not making oil, no puffs of smoke out the oil fill, no blown out dipstick from a broke piston. fuel return isnt all that much even taking the main return line off. i was actually surprised at that. its just a little trickle.
at first i thought it might be tuning as running the stock tune would quite it down so i messed with the tuning a bunch, increasing rail then decreasing (above and below stock), adding or subrating timing (above and below stock), and attempting to see if messing with commanded idle mm3 would do anything. So what i thought fixed it was lowering everything as it quiet it all down and it was good for a day, then it came back just as loud as before. If you shut cyl 5 off, knock is completely gone and she sounds great besides the miss. So i tried some injector clean thinking maybe they are a little gummy after 25k. made absolutely 0 difference. balance rates are no higher than -+2.0 accept for cyl 5 which is positive 6.
at this point, im thinking the copper seal is no longer sealing in the cup for the injector or the injector is bad its self. the positive number makes me think compression is a little lower in that cyl from it not sealing or maybe a weak coil on the injector.
anyone else have any ideas to double check? ive tried to do most of the diag before posting. valve cover comes off tonight. least its on the easy side
