Lope at idle after new injectors
- Thread starter millerman04
- Start date
T25 IIRC the whole thing would be better if it wasnt for that plastic harness that goes right over the top.
On the cold start this morning it was about 10 degrees out. Truck fired right up. Lil blueish/gray smoke for a bit, then cleared up to a clear color. Never missed a beat in idle, least that I heard anyways. I wasn't outside much longer after it started. I'll do some checking of the lines up on top when I change the oil. I'll either check the fuel pressure regulator with my efi, or my buddies cts.
A LB7 with a shimmed FPRV can cause lope with new injectors. The old injectors could have returned fuel slightly quicker making the rail pressure low enough not to lope. And the remans are up to spec again raising rail pressure because of the shim. The smoke will appear when too much fuel is being forced into the cylinder and temps aren't up where they should be to burn it. Start with removing the shims and go from there.
How's does the relief even come into play at idle? if its set to open and say 26K how does it have anything to do with the pressure at idle? want to learn something here.
The relief is controlled by a spring. So the spring gets compressed more as the pressure climbs to 26k, gradually allowing fuel to return back to the tank as needed throughout the rail pressure range. Its not a waste gate style control for rail pressure. Meaning it wont stop fuel from returning until the pressure reaches a set pressure (26k for example) and then open. That's why some need shim kits (LLY,LBZ ect.) to hold the rail pressure. The spring opens easier (sooner) allowing more fuel to return quicker in the rail pressure range. Fuel will start returning as soon as pressure climbs high enough to push the spring a little. Even at 4-5kpsi. Hope this explanation helps some.
Whether its the FPRV returning fuel, or the injectors, or CP3, fuel must return to the tank at idle (and at all times) for the truck to run correctly.
Whether its the FPRV returning fuel, or the injectors, or CP3, fuel must return to the tank at idle (and at all times) for the truck to run correctly.
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Im still waiting on the time to get to the truck to remove the shim kit I put in. I only did it to try and rule out having to replace my injectors. I should get to it here next week. The lope has seemed to have went away. So maybe I still had a lil air in the system somewhere. I wasn't a bad lope. Just a bit noticeable.
I'm not sure to let the shim kit in or not. Yes the truck runs fine. Starts fine too. Just don't want it to lead to a problem down the road.
I'm in the same boat with my LMM. I was told it's a known issue with the LMM sometimes on larger injectors (I did 40 over tips). Sometimes it's not bad, sometimes awful up and down, but it's always the RP bouncing higher than commanded never lower. When it warms up I plan on looking for any fuel line pinches or leaks just in case. My mm3 is always bouncing around from like 20mm3 down lower and back up up again.
Hopefully yours continues to run well :thumb:
Hopefully yours continues to run well :thumb:
My buddies truck has the same issue.....kinda, it lopes at idle till it warms up then it's ok until you put it in drive then it lopes again, it did this before and after new injectors and fpr! running outta ideas on this one
You can rescale current on fuel pressure regulator to cure your lope. This will most of the time work unless the reg is shot.
I wondered about that. this is a new regulator that has the 90 deg connector on it. any tips on where to set the scale? it was loping before and now its not as bad but still doing it just seems to be quicker.