Looking For A Little Help

[WisconsinHick1]

I recently tuned a buddies LMM it is a stock LMM doesn't even have a lift pump. For some odd reason now on his big tune (That's all he runs on) while driving down the road it will slow down and no matter how hard he presses the pedal it wont speed up then all of a sudden it'll start speeding up again. It is inconsistent as too how much it slows down also.

I don't think it would be tuning related but could anyone give me any idea's as to what I might want to look at? I could email the tune to you for you to look over. I haven't rode in the truck since I tuned it so I don't have any logs showing what happens. Maybe this weekend I can get some.

[THEFERMANATOR]

Check rail pressure to see if maybe the fuel lines are collapsing. Otherwise your going to have to find out if it is a defuel of some sort, or limiter causing it.

[Mitco39]

If rail pressure is fine and everything else checks out just start over with a clean base and full flash it in.

[WisconsinHick1]

The weird part is it's at constant speed 65 mph in or not in cruse. It was a clean fresh tune from Tony at Ridge runner. I did a Cal flash after a slight alteration but I will try a full flash.

I also told to try it in the base tune where I didn't touch anything other than limiters. He also has a new fuel filter on there to make sure that wasn't it.

[GMC-2002-Dmax]

That tune was right off TIS, updated file from GM.

So it was never tuned with anything, just as if GM replaced the ECM with a new one

[Mitco39]

I thought it was your tune you were making and flashing. I would just contact Mr Tony himself. He knows his stuff.

[GMC-2002-Dmax]

The weird part is it's at constant speed 65 mph in or not in cruse. It was a clean fresh tune from Tony at Ridge runner. I did a Cal flash after a slight alteration but I will try a full flash.

I also told to try it in the base tune where I didn't touch anything other than limiters. He also has a new fuel filter on there to make sure that wasn't it.

Try your tune as a single tune file, not a DSP5 first.

Also log vane position when the issue happens, if it moves to 100% then its an underboost and if you shut off the P0299 it won't be as apparent as to what is going on.

Typically the LMM's will suffer from Underboost conditions more so than any other model, especially when deleted.

If you want an answer start with a log of all sensors and vane tables as well as the fuel system.

Tony

[WisconsinHick1]

Alright I'll give that a shot thanks for the direction!

[WisconsinHick1]

I thought it was your tune you were making and flashing. I would just contact Mr Tony himself. He knows his stuff.

Tony gave me the clean stock tune and I built off of that.

[30 RUM]

Check to make sure that you don't have any values but 0 in the first row of your torque reference tables. Recently I did a LMM and when it populated the DSP tables regarding the 5th tune, I had some strange values in the elevation torque tables. I don't have my computer in front of me, if I did I would tell you the exact tables I had problems with. Has he had any check engine lights? I had a P0606 (internal ecm fault). I chalked my issue as a fluke, it will be interesting to see if you have the same problem.

[WisconsinHick1]

In my base tune the first row is 0 but in my DSP positions they have a low value in the first row. No codes though. But I will change the values to 0 and see how that goes!

Thanks!

[30 RUM]

That was my problem, it was only on the 5th tune or number 4 in the program. I missed it because I only altered the lower elevation and not the mid/high. When the ecm would blend between low and med it would cause the problem. Let me know if*that works for you.