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weird hicupping / random rough idle

985 views 5 replies 2 participants last post by  White95f250 
#1 ·
i have a 97 7.3 with 200k ish miles, in the past few months i've noticed when it's idling my rpm's will fluctuate slightly & when i accelerate it sounds like its hiccuping almost or like a slight chug or miss? a couple times it was pretty severe and felt like it was bucking back. it seems to be slightly better when the motor is warm but it will still do it when its warmed up. the truck wouldn't start awhile back so in trying to figure out what it was i replaced the ICP, IPR, IDM, new fuel pump, & the CPS (i got it running) i was hoping in the process that i would have fixed the rough idle but it still persists, i'm not sure what else to look at? the UCVH is good. any thoughts? thank you in advance
 
#2 ·
Triple check the valve cover connections. I just soldered on a new connector because the pins were severely melted. Looked ok but once I unplugged it I saw how bad it was.

You could also do a buzz test and listen to see if any injector sounds weak.

What I do is drive it hard for a few miles to keep everything cleared out. I think that's the only reason my stock injectors have lasted this long. Lots of hard driving!
 
#3 ·
i re-checked the valve cover connectors and they all look good, would you suggest taking the valve cover off and re checking underneath also? i unplugged the exhaust back pressure sensor and it didn't help either, the surging has become more severe and shakes the truck now
 
#4 ·
Have you hooked a scanner up to it and attempted a buzz test? What's fuel pressure at? What's HPOP pressure and IPR % while it's running?

A buzz test will eliminate the need to remove the valve covers. You can give a visual check but a buzz test will check from the IDM to the injector.
 
#5 ·
my apologies i forgot to mention i had a buddy who brought his scan tool over and we did a buzz test and they all sounded fine, i'm not sure if his scanner is capable checking HPOP pressure or IPR % but i'm gonna ask him. if not i might have to bring it the shop and have them see if they can figure it out
 
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