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+--- Thread: 870 air fuel issue (/showthread.php?tid=10062)
870 air fuel issue - Bradar - 04-06-2025
07 isx 870 having issues with over fueling. Loaded I very seldom have an issue usually empty or bobtail. The problem is when you are going down a hill or 1/4 throttle and you go to accelerate and no power just a lot of black smoke out of the stack. It will clear out but it takes a few seconds. It started this 2 weeks ago so I done an injector leak down test and found number 5 injector was leaking so I replaced the 4,5 and 6 injectors. The truck idles better but that’s about the only change I have noticed. It still has the over fueling problem. So I done a cac leak test and found a small leak on intake clamp and oring fixed that still the same issue. The boost controller has sufficient air pressure and the truck has 32psi of boost. Has anyone ever had this issue? Thanks!
RE: 870 air fuel issue - tree98 - 04-06-2025
32 psi of boost is low for an 870. I would suspect the turbo control box is going bad, could be the air actuator is bad, or maybe the VG ring is hanging up.
RE: 870 air fuel issue - Rawze - 04-07-2025
boost only at 32 psi is also an indicator of an Auxiliary emissions derate.
If it s de-mandated, the chances that its a bad delete are more than 90%+.
here is likely your issue...
ref: https://rawze.com/forums/showthread.php?tid=8370&pid=72522#pid72522
why they do this is described in this post...
https://rawze.com/forums/showthread.php?tid=7355&pid=64964#pid64964
Get with forum member 'running rough' as her is the resident CM870 specialist for those old GTIS3 products.