Reduced Engine Power, no codes

[kirker912]

I have a 2008 2500HD that has me stumped. It will go into "reduced engine power" every few minutes. It will even do it at idle. It isn't throwing any codes.

I have done the following:
cleaned the MAF
Replaced the throttle sensor/peddle
Flashed ECM and TCM with EFILIVE
Logged data when the problem happens
Rail pressure holds well

I still suspect something to do with the throttle position sensors because they do not read 0 at idle or 100% at WOT and they don't perfectly match either.

Mods are:
Air dog 165
Exhaust
Down pipe
EGR delete
PCV
Batmowheel
EFILIVE
Cold side IC pipe
Race fuel plug
Transgo Jr

Anyone out there have any ideas?

 

[gmduramax]

Turn the codes back on. Replace the maf sensor

 

[03badmaxxx]

Do yourself a favor and try a different MAF. If it doesn't work, return it. I've had similar problems like this with a few trucks at the shop and all of them came down to the MAF. cleaned them, no codes or anything but would throw reduced engine. Went over the whole wiring harness, all sensors and couldn't find a damn thing wrong. Finally on a whim changed the MAF and it set the truck right.

 

[NKlamerus]

When is the last time you replaced the fuel filters and have you bought diesel anywhere odd lately?

 

[Harbin_22]

Check for codes with EFI in the actual scan tool part, not just the handheld. I have had a few codes that didn't set a light, didn't show up on the V2 by itself, but were there when I used the scan tool software.

 

[NC-smokinlmm]

Is it limping in park? Or is it only limping when you put it in gear?
There are 2 types of limp, one is engine related the other in trans. We need to figure out where to start before any advise is given...

 

[kirker912]

It will do it while driving or while idle in park.

Diesel always comes from the same place except long road trips.

I'll runs codes with the scan software this afternoon and see what it says. Is there a good way to tell if it is engine or trannie causing the problem if no codes are shown?

Fuel filters are a month old. About 3k miles.

 

[NC-smokinlmm]

Its an engine limp it coud be from faulty emmisions equpiment or inproper tunng for what has been removed.

LMM's can be tricky. What's the map sensor reading?

 

[kirker912]

No codes came up with EFILIVE and the scan program running. I hope to have a new MAF tomorrow try. I have a new ECM on the shelf I may swap as well though I don't think that's the problem.

 

[kirker912]

Swapped the MAF and it ran for 3 miles before "reduced engine power"

 

[NC-smokinlmm]

What is the map sensor reading? LMM are wierd about the map and maf, if either is off they freak out...

 

[kirker912]

MAP varies from 12.2 to 28 while driving and MAF from 4.9 to 36

The problem has occured with a MAP from 14.8 to 17.7 and MAF from 15.9 to 17.2

Idle map is 12.6 and MAF is 5.17 to 5.38

 

[Bobo]

MAP varies from 12.2 to 28 while driving and MAF from 4.9 to 36

The problem has occured with a MAP from 14.8 to 17.7 and MAF from 15.9 to 17.2

Idle map is 12.6 and MAF is 5.17 to 5.38

Have you reset all your codes to stock values so the ones that need to report are there?

Do you see anything odd with the fuel rail pressure desired vs actual on the data log?

 

[kirker912]

I flashed the TCM and TCM with original files from Tune File Depot and there was no change.

Actual and desired match almost perfectly.

The first day that this happened it was pulling a small cattle trailer empty. Is it possible for the trailer break controller to cause this? We have since unhooked the trailer and problem persists.

 

[NC-smokinlmm]

What Bobo said^^^^

I'd bet that sucker is wanting to throw a p299...

 

[kirker912]

Pulled ECM. Cleaned connectors, logged a bit, checked fluids.

Going along with the P0299 idea. It isn't appearing but if I have a leak in the Y-Bridge then the MAF data is off....

 

[GMC_2002_Dmax]

Log the vane position, if it goes to 100% and then shows reduced power it's underboost

 

[kirker912]

Here is the latest log file. It was logged while pulling an empty 24' gooseneck. There is a marker about the time the error occur.

 

[kirker912]

The problem is finally solved. It was the ECM. Replaced it, flashed the same tune, updated injector data and its been running for two days now without a problem. Thank you all for the help.