LB7: Lb7 loping/running rough under light throttle

[Bustedknuckles]

I just noticed today that if I'm idling and apply SLIGHT throttle, barely enough too raise the rpms my truck will start shaking and running rough, any more and it goes away and it runs smoothly at idle. It acts almost like it has a mild lope tune. Has anyone else experienced this? Is it normal or is it a bad sign? TIA

 

[McRat]

You need to check injector balance rates. Does the exhaust smell more like raw fuel than it used to?

 

[Bustedknuckles]

No, no smoke at all on startup either. I have a airdog too so I'm hoping its not injectors! I just thought about that I forgot to put additive in this tank......

Sent from my Evo while driving.

 

[McRat]

With an LB7, additive is a good idea.

Check the usual, aircleaner, boost leaks, etc, but 90% of the time it's an injector.

 

[McRat]

Oh, and if you have a harness box (Edge/Banks/etc) take it off, and see if the problem persists.

 

[Bustedknuckles]

I have a dsp5 with tunes from rob coddens so thats ruled out. I'll check balance rates tomorrow and expect the worst. Thanks for your advice!

Sent from my Evo while driving.

 

[McRat]

Reflash and see if it persists. Sometimes the ECM can get stuff "stuck in it's throat", and a reflash can clear certain tables that can't be seen. Rare, but it happens.

 

[Evan@InglewoodTrans]

I just noticed today that if I'm idling and apply SLIGHT throttle, barely enough too raise the rpms my truck will start shaking and running rough, any more and it goes away and it runs smoothly at idle. It acts almost like it has a mild lope tune. Has anyone else experienced this? Is it normal or is it a bad sign? TIA

Ironic this question came up Ive had the same issue for a while. It doesn't do it unless you just barely set your foot on the gas it's strange.

 

[Bustedknuckles]

Ironic this question came up Ive had the same issue for a while. It doesn't do it unless you just barely set your foot on the gas it's strange.

Right, not even enough to make the tach move.... I'll try the reflash and see if that fixes it.


Sent from my Evo while driving.

 

[Evan@InglewoodTrans]

Im going to try switching tuning then go from there.

 

[Evan@InglewoodTrans]

I hadnt had the problem for a while and I switched tuning the other day and noticed it again so i think it could be it. Balance rates are good and the truck runs perfect otherwise.

 

[Bustedknuckles]

I switched tunes and it didn't change but I havn't reflashed or checked balance rates yet.

Sent from my Evo while driving.

 

[Evan@InglewoodTrans]

It's not a tuning issue for me I just confirmed that. I'm not that concerned the truck runs great it's just strange.

 

[DIESELMAFIAPER.LB7]

Mine will do it once in awhile as well I don't know what it is

 

[Mike_S]

If you apply enough throttle to register 1 percent, it disables the balance algorithm in the system. You can see this effect if you have efi live, watch the balance rates as you depress the throttle, the rates will all zero out corresponding to the rough idle, and one percent throttle give or take. Every LB7 that i have been in does this, and most LLYs as well. Can't speak for any engine platforms above that as I have not remembered to try it. It is a good on the fly way to check your injectors, if it is an erratic rough idle chances are you have nothing to worry about. If it is a definate or noticeable "miss" then you best be checking your balance rates, or having the thing checked out. Although this is a very very subjective and dirty test, it does give you an idea if you should drag out the testing equipment.

 

[1chevy02]

Mine and a couple others I know of will also shake slightly when you barely press on the accelerator.

 

[Jscherbs]

If you apply enough throttle to register 1 percent, it disables the balance algorithm in the system. You can see this effect if you have efi live, watch the balance rates as you depress the throttle, the rates will all zero out corresponding to the rough idle, and one percent throttle give or take. Every LB7 that i have been in does this, and most LLYs as well. Can't speak for any engine platforms above that as I have not remembered to try it. It is a good on the fly way to check your injectors, if it is an erratic rough idle chances are you have nothing to worry about. If it is a definate or noticeable "miss" then you best be checking your balance rates, or having the thing checked out. Although this is a very very subjective and dirty test, it does give you an idea if you should drag out the testing equipment.

Great info here thanks

 

[stephen]

I have same thing just above idle and also drone/vibration at cruising speed 55-75 if I shift into neutral it goes away. Any body have an idea what's going on with my lb7.