Lope at idle after new injectors

millerman04

millerman04

< The Man Cave
Jul 14, 2010
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Just spent this past Friday and Saturday replacing my injectors. Got them from Lincoln Diesel. Excellent choice I may add. Got the truck back together Sunday around 2 am. Now I have a lope at idle. Seems to clear up after truck warms up. Only does it when you start it cold. Could this be my fuel pressure regulator acting up? Or maybe a lil air still in the system? Thanks all!!
 
DAVe3283

DAVe3283

Heavy & Slow
Sep 3, 2009
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Boise, ID, USA
Do you have EFILive? If so, log the commanded and desired rail pressure, injector pulse width, timing, and main fuel rate. If it is your fuel pressure regulator, you will see the commanded fuel pressure staying constant, while the actual jumps up and down in a sawtooth fashion.

Something else you could try is putting a little two stroke oil in the fuel. That helped my fuel pressure regulator limp along another 10,000 miles or so. I used a 500:1 mix, or 6-7 oz of two stroke oil per tank. The cheap two stroke oil works fine.
 
catman3126

catman3126

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Jul 24, 2012
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I jus thad a guy with this issue and he replaced the FPR and it didnt change. he is running my DSP5 tune in an 03 and for the first 3 days it had no lope and then started. I flash his exact tune in my 03 and had no lope issue. I will ask him if he got it figured out. one thing that I had happen was the valley lines were brittle and crack and as soon as I replaced the lines the lope went away. this guys 03 had the same thing and he said "yeah mine lines looked dry rotted but they werent leaking" to which I replied well the suction line is just that and never has pressure on it since there is no lift pump. he said shit so I gotta go back in there?
 
WolfLMM

WolfLMM

Making Chips
Nov 21, 2006
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Yeah. I had the same problem. Mine was the fpr. I also had dry and cracked fuel lines in the valley.
 
millerman04

millerman04

< The Man Cave
Jul 14, 2010
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What gets me is it never did it before the injector swap. Now it only does it when you cold start it. Smoothes out after it warms up. Could it be my shimmed fuel pressure relief valve?
 
millerman04

millerman04

< The Man Cave
Jul 14, 2010
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Just a lil bit of smoke after it starts. Goes away after it warms up. I thinks it is a touch blue but would hafta look again at next start up.
 
catman3126

catman3126

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Jul 24, 2012
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millerman04 said:
What gets me is it never did it before the injector swap. Now it only does it when you cold start it. Smoothes out after it warms up. Could it be my shimmed fuel pressure relief valve?
Click to expand...

Shimming a rail relief on a LB7 isnt a good diea since the injector bodies are weak as it is. crack one and fill the crank case and you'll be right back in there.
 
millerman04

millerman04

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Jul 14, 2010
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Just started it now, and everything seems fine. Wasn't no smoke at startup this time. Its 17 degrees here and the winds blowin. I'll make an update in the am after I start it. It seems to do randomly anyways. It'll idle fine for a lil while, then lope some, then quit. Maybe i'll see about un-shimming here sometime soon. Just a pain in the arse!! What's the size of the bango bolt gasket on the pressure regulator? Will one off the ficm fit?
 
catman3126

catman3126

Ehhh?.... You don't say?
Jul 24, 2012
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you can usually re use that if its not to smashed up. but no the FICM bolt is different size (smaller) so it most likely won't work.
 
millerman04

millerman04

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Jul 14, 2010
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Well hopefully one more time wont hurt. I definately dont wanna screw up my new injectors thats for sure. I only shimmed it in hopes that it may have fixed my problem. But it didnt. New injectors did tho. Haha
 
Yngdmax92

Yngdmax92

Active member
Sep 26, 2013
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I honestly dont think a relief valve will make the truck lope. It probably has something to do with the fpr or like one of the other guys said air leak some where maybe in the rubber hoses or what not. Do you have anything to scan the truck with? like watch actual vs desired on fpr or rail pressure. And see what percentage the fpr is at idle
 
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