CAT 6NZ misses/shudders under loadI have a 2003 Peterbilt 379X. CAT C15 6NZ Engine. I'm 19 months into 4 year full platinum rebuild. Here's my symptoms....
Answer to "My C15 has hesitation/miss/shudder on hard pulls & acceleration why?"i FOUND OUT ACCIDENTALLY THAT THERES A UPGRADE TO THE FUEL PUMP SPRING. i BOUGHT IT, INSTALLED IT IN MINUTES AND IT BOOSTED MY FUEL PRESSURE TO THE POINT WHERE MY ENGINE IS RUNNING CONSIDERABLY BETTER. i HAD THE SAME THING GOING ON WITH MY C15 6NZ. Parts guy at CAT said alot of guys with 6nz engines are being wrongly told the fuel psi should be 95 psi, when in fact it should be 115 psi for a 6NZ. Now im running 125 PSI and its much much better. The spring is hugely over priced, its a darn spring the diameter of a pencil under 3 inches long (but it comes with a new cap plug….WOW.. NOW ITS WORTH THE $93… “ NOT”…. (but it works..try it )
Answer to "My C15 has hesitation/miss/shudder on hard pulls & acceleration why?"My 2003 C15 6nz has same issues. Changed frame mounted fuel filter head (Peterbilt said was sucking air) Next they said it's a bad fuel line between fuel pump and tanks. I changed all fuel lines. Next they said it's a bad fuel pump, they changed it. The list is endless. Still it pops and stumbles under load. 3X CAT drove with me, cutting out injectors with no resolve. Here's my unique symptoms. I'm 19 months into a platinum rebuild by CAT. New Tranny (18) behind it. 2 new diffs. Balanced driveshaft. New Ujoints & hangar bearing. New load leveling valve. Pops, stumbles and power goes down under load or pulling empty trailer. Ease my foot off accelerator but still maintaining road speed on a flat surface and all is fine. Press down a touch to increase speed and pop...shake and shudder. Here's the clincher... Idle for a few hours and head out loaded and my engine runs smoothly and perfectly , for 2 to 5 minutes. Last week I had a entire day of perfect smooth powerful engine running, for unknown reasons. Tried...