Hi guys this is my first time posting I hope someone can help. I have a 2008 duramax LMM. I have an intake,exhaust and H&S mini max tuner I'll try and explaine my issue the best I can. I have a 6000 pound holiday trailer and I'm getting 41L/100km I can't maintain any speed going up a slight hill to a larg hill even flat ground it has a hard time the transmission temp is getting up to 230F. I tied to post a video of my truck unloaded going up a small incline and it shifts from 6th,5th,4th back to 5th,6th,5th,4th then repeates again and again till I hit the top I even have had it shift from 6th to 5th on flat ground. I have taken it to our local shop they said their is nothing wrong with it. Any help or direction would be great sorry if I posted this in the wrong spot. Thanks
Bad power transmission hunting?
- Thread starter Mx_master
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Ditch the mini maxx. Get a good set of EFILive tunes. those mini maxxes along with edge, banks and bullydogs love to destroy transmissions. My Dad had a Banks tuner on his LMM and now his trans hates him.
Ditch the mini maxx. Get a good set of EFILive tunes. those mini maxxes along with edge, banks and bullydogs love to destroy transmissions. My Dad had a Banks tuner on his LMM and now his trans hates him.
Have you changed fuel filter?
Yes I have changed fuel filter and oil a month ago. I also put a brand new Airaid filter on just incase it would help. I did buy new internal and external transmission filters but haven't put them in yet.
All the shifting up the hill Is in cruise control set at 120km/h with no load on truck
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I'm getting 8Mpg hauling a 6000 pound trailer somthing is wrong. The shop said my injectors checked out fine.i only have 129,000 km on the truck (80156 miles)
First of all why do you have cruise control on going up hill towing a trailer. That's more than half your issue.
I don't I'm empty that's the issue l. When hauling the trailer I never use cruise control and it can't maintain speed. It will down shift on flat ground with the trailer to 4th a duramax should have no issues pulling a 6000 pound trailer.
Sounds like a fuel problem to me.
eh, you'd be surprised how many people keep cruise control on and still pull hills
^^this
time to start looking at rail pressure (actual vs desired).
I thought maybe a fuel problem as well until I ate through a full tank of fuel pulling my trailer in less then 3hrs on a 95% flat highway. I figured I was getting lots of fuel but not transferring the power to the wheels I'm no mechanic or anything I been just guessing haha.
How does it do with no programmer
I was told I can not run with out a programer as I have the DPF delete. So I never tried to be honest just in case it screws somthing up. This is the second programer on the truck the first one was some shity Godzilla thing the previous owner had I was told it was my programer causing this issue so I bought the H&S one a few years back and it didn't solve it. The issue wasn't this bad last year so I'm not sure why it just got worse.
unfortunately we cant just tell you "this is your issue" without some diag from you or someone working on the truck. fueling needs to be logged, history of codes checked, and so on.
I had the shop run diag yesterday and they didn't find a single issue they said injectors seem good no stored engine codes nothing. So now it's booked to go into gm tomorrow and see if their computers can find somthing the other shop couldn't. The only code that I ever seen come up was low fuel rail pressure when playing with my programer at the highest setting and hammer the throttle down it will through that code other then that the check engine light has never come on.
I'm with him, sounds like a low fuel pressure issue, if it is my guess on the cause is more then likely high return injectors, use mini max to watch rail psi!
The dealer will more then likely blame your tuner. And then proceed to waste a bunch of your time and money.
You are losing rail pressure. Do like everyone has said and log your rail pressure. Desired and actual. And do it while towing up hills.
Possible causes include,
Leaking fprv
Worn CP3 pump
Pinched or restricted supply lines
Worn injectors (high return rates)
Restricted tank vent (in the cap)
Low rail pressure, and power will also result from a faulty fuel temp sensor on an LMM.
And I don't believe that your injectors are good just because the previous shop said so. If they couldn't diagnose your issue I highly doubt there ability to determine good injectors from bad ones. Not saying your injectors aren't good, I just wouldn't trust the previous shop 100% on that just yet.
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Okay awesome thanks a lot for your help guys ill keep an eye on the fuel rail pressure and see what happens. The previous shop when I asked how they test the injectors didn't really have a answer they said it's not much of test but they seem good it was my first time going their looks like I won't go back their.
You most likely do have a fueling problem with that code popping up. Just my guess.