LMM: LMM Falls on its face, then comes back when I let off and get back into it

[iambatman]

I have an EFI live tune on my 08 LMM with the 5 position switch. When I go "extreme" it falls on its face after accelerating hard for about a block. Then I lift off the accelerator and it goes like hell again. Sometimes. Could this be injectors or other fuel problems? I replaced the fuel filter head and filter, and it was better for about a day. Then right back to the same issue. Help please!!!

 

[A. Stock Lbz]

How big is the tune? Do you have a lift pump?

 

[iambatman]

No lift pump. Not a huge tune, as the trans is stock and wanted to keep it together. I had it done at a local diesel shop, and he figures it's about 80-100 hp gain in "extreme"

 

[iambatman]

I failed to mention before the tune, accelerating as hard as I could to get in the interstate, it would do the same, just not as noticeable. Now with all the tuning done it does it in all modes, just amplifies more the higher the setting

 

[A. Stock Lbz]

Sounds like your rail pressure is dropping. I would take it back to the shop who tuned it and have them data log it so see.

 

[iambatman]

It still is blowing black smoke when it's struggling. Could I be sucking air or have a restriction in my line?

 

[A. Stock Lbz]

How many miles on the truck? Is all the maintenence up to par? Air filter and maf clean? I would go get it data logged and that should give you some idea what it is. New fuel filter?

 

[A. Stock Lbz]

A 80-100 hp tune should be fairly smoke free in my opinion.

 

[iambatman]

100,000. All maintenance is done and up to par. I appreciate the info. I will take it in when their new shop is built. I'm out in the middle of nowhere and they are the only reputable people around. So I'll have to wait while they move from one shop to another sadly. When I replaced the fuel filter and its housing it ran great for a day or two. Then back to the same old same old. It did it 100 percent of the time before that and after. That's what makes me think it's in the lines or something

 

[iambatman]

Also it is pretty smoke free, per my request as well. But it does smoke a little. The smoke stays visible during my issue

 

[A. Stock Lbz]

I don't know if the lmm have the fuel line problem but I had to change one on my lbz were it changed from metal line to rubber. It would suck shut.

 

[iambatman]

I just know nothing about diesels so I came here to learn. I build a lot of cars and gas engines so it's out of my realm. Many thanks for your help

 

[iambatman]

Another thing I forgot to mention is that my change fuel filter indicator will come on every time

 

[iambatman]

And in some occasions I will get a reduced power indication, although this feature has been tuned out I still get the warning.

 

[JoshH]

Low rail pressure. More diagnostics would be required to tell you what is causing it.

 

[Rancelot211]

Subed

 

[Rancelot211]

How fast are u going when this happens. More details.

 

[iambatman]

It happens at all speeds. It's 100 percent of the time under full acceleration in all 5 positions

 

[iambatman]

Goes like hell for a short time then without fail it falls on its face. I lift the throttle for a few seconds, get back into it, and it goes like hell again. For a longer time then fails again. It's like the fuel gets replenished in the rail then i starve it again. A few times of doing this I'm near cruising speed then I can run full throttle again and it will pull strong until I'm going over 100.

 

[Awenta]

If your shop can't figure it out get a new tuner. Also get a lift pump

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