LB7: lopey idle

[ZeroGravity58]

My truck has Done this for awhile. It park/neutral it idles perfectly fine. In drive it lopes and I'm tired of it now that I'm driving it a lot more. I can't figure it out. Anything specific to look for? I have 30 over in it. Fuel pressure at idle right now is 4950.

 

[madmatt]

sounds like a failing fuel rail pressure reg

 

[ZeroGravity58]

Fuel pressure reg is a lbz with 5000 miles on it. I can't remember because its been awhile but I might not of gotten it straight from when I changed regs. I adjusted the b1010 table and got the idle pressure right. I just know I'm missing something else.

 

[SparkZ03DMAX]

I kinda have the same problem. But my #8 injector is at 15+ mm3, I figured one cylinder getting alot more fuel than the others would cause a lope. I'm going to be getting a whole new set of injectors this coming month so I'll see if that was causing the lope. I replaced my FPR with a LB7 FPR back in June so I know it isnt bad.

Check your balances maybe that will show something?

 

[MACKIN]

I have an occasional lop that I believe is the Regulator on the CP3 sticking but it does it at idle ,drive and neutral. A quick stab of the go peddle eliminates it. Odd that it will do it in drive and then when you put it in park it goes away?

I'm thinking you should perhaps look at your balance rates. You have 30 over injectors if I read your post correctly.

I know when I put my Tech II on it when it lops the actual and command pressure is all over the place if I remember correctly been awhile since I checked it out. I usually just stab the go peddle when it does it. Mine will lop enough to push the truck with light brake pressure.

 

[MACKIN]

Fuel pressure reg is a lbz with 5000 miles on it. I can't remember because its been awhile but I might not of gotten it straight from when I changed regs. I adjusted the b1010 table and got the idle pressure right. I just know I'm missing something else.

I know squat about EFI check your balance rates. I was typing while the other gent posted the same.

Thats what I'm leaning to unless it's tune related.

 

[SparkZ03DMAX]

I know squat about EFI check your balance rates. I was typing while the other gent posted the same.

Thats what I'm leaning to unless it's tune related.

Yeah mine only lopes in drive. But my #8 injector is pushing a crap load of fuel (which why I havent drove it in 2 months) so I figured that was the problem, we'll see what it does after I get all new injectors.

 

[GeorgiaDuramax]

Mine does the exact same thing.

 

[TheBac]

Might still be the FPR table. You may want to play with the off-idle values a bit, see if that clears it up.

I was never able to completely tune my lope out, but I started running some additive in my truck this winter and it lessened the loping quite a bit. Still rears its ugly head, but not as bad.

 

[GeorgiaDuramax]

The FPR is what I was thinking.

 

[sparepartsracing]

my truck does the same thing also...just never bother to looked into it

 

[Mike_S]

I'm thinking a combination of increased fuel volume due to larger injector nozzles, as well as the FPR voltage tables not being correct enough. Start by logging commanded vs actual rail pressure. If they don't coincide then you should be looking at that voltage table, however if they are close and not bouncing all over the place then you need to start pulling pulse-width in your main fueling tables.

 

[sparepartsracing]

I'm thinking a combination of increased fuel volume due to larger injector nozzles, as well as the FPR voltage tables not being correct enough. Start by logging commanded vs actual rail pressure. If they don't coincide then you should be looking at that voltage table, however if they are close and not bouncing all over the place then you need to start pulling pulse-width in your main fueling tables.

im getting efi tomorrow and my truck is stock other than the lift pump and boost increase valve so as soon as i figure out how to log ill post it up because ive had this problem with my truck and my cousin has it with his lly but his pushes threw the brakes almost

 

[Mike_S]

im getting efi tomorrow and my truck is stock other than the lift pump and boost increase valve so as soon as i figure out how to log ill post it up because ive had this problem with my truck and my cousin has it with his lly but his pushes threw the brakes almost

If your truck is stock, no programming or anything like that and it is loping then more than likely you have a failing FPR (or FCA...fuel control actuator to the dodge boys...LOL!). They will tend to stick in a slightly open position causing higher than commanded rail pressure and hence more fuel than what is being commanded...this causes the engine to overshoot its target idle RPM and then chop the fuel delivery completely until the RPM falls back below the target desired RPM, at which point it starts the cycle all over again.

This is the basic cause of most all lope idles, excessive fuel in one way or another...high rail pressure, longer than normal pulse widths, or larger nozzles will all cause a lope.

 

[ZeroGravity58]

Ok I did some logging today while I was stuck in line for an hour to get into the local landfill. At idle in neutral the truck commands 4950psi and the actual is +-50 psi. When in gear it was commanding 5150 but the pressure was all over the place around +-500 psi. As stated before it idles fine in park neutral just not in drive.

 

[ZeroGravity58]

my injectors are fine also.+- 3 in gear. I just replaced a few of them a couple months ago.

 

[duramaxdiesel]

I had the same issue. But like Tom said using additive really cleared it up. I've used it ever since (before the motor blew) and never had the lope come back.

Nick

 

[ZeroGravity58]

I use powerservice at every fill up and two stroke every couple. It has changed anything. I don't think the fprv is bad it just something in my tuning I can't figure out

 

[Mike_S]

I use powerservice at every fill up and two stroke every couple. It has changed anything. I don't think the fprv is bad it just something in my tuning I can't figure out

Try pulling some pulse width right around idle, or mess with the rail pressure valve current table some. Either option will probably help get the idle smoothed out. :thumb:

 

[ZeroGravity58]

ok guys i still need help. i havent had a whole lot of time to mess with it but i cant fix it. I tried messing with the pressure, FPRV current, removing fuel etc. I cant get rid of the lope. I can post a log of the pressure jumping all around. Its freaking annoying when im sitting at a red light. as soon as its off idle it runs great.