Please help! Loss of power... at my wit’s end

Mryan1789

New member
Mar 9, 2021
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Hi there, this is going to be a bit wordy and I apologize for that.

The truck:
2005 ccsb
230k miles
4” straight pipe
Egr blocker plate
Finger stick
K&n air filter
S&w turbo mouthpiece

I’ll try to sum this up quickly:
Truck was bone stock when I installed the turbo mouthpiece; no issue.

3k miles later I installed a 4” straight pipe, and on the way home I got 2 egr codes(p0401, 0404) and a low boost code(p0299).(this resulted in limited power)

I had not planned on tuning the truck, so I bought a finger stick that came with an egr block off plate.I installed the finger stick, put the block off plate in, and sprayed my MAF sensor with MAF cleaner spray all at the same time. The next day, no more egr codes or low boost codes, but I had a MAF code(p0103), which also seemed to limit my throttle. The truck would still rev out, but had less power. It was more than driveable so I kept driving it for a couple weeks. I even tried replacing the MAF with no change.

Fast forward a couple weeks and I removed the finger stick, and got the truck tuned with an EFI live tow tune(single tune). Once tuned, it briefly threw a p0100 code, which didn’t last, then a p0102 code which didn’t stick around either. Have about 100 miles on it since then with still no code.

The truck is now much more responsive, but once it hits that certain throttle/boost/something, it still just cuts power and only seems to allow roughly 50-60% throttle.



Here’s the tricky part: when I first start the truck, whether it’s from overnight or a couple hours, it will boost HARD and pull like a freight train. Like clockwork, after 2-3 miles of driving, it starts falling on its face again. Will drive like a brand new truck all day long, but if you give it a little too much throttle, it spools up and pulls hard for 1/2 a second, then the smoke and power immediately cut out at the same time and it defaults to roughly 50% throttle. It’ll set you back in your seat when it originally spools then it immediately cuts power and only allows half.
Once again, if I park it for a couple hours, it’ll run perfect for the first five minutes or so, then start limiting again under hard acceleration.

My tuner also tried unplugging the MAF sensor altogether and it made zero difference, the truck still would drive like normal until you tried to accelerate at any rate slightly over driving grandma to church, and the power significantly gets cut back.

I have tried 3 different MAF sensors, 2 being new and one being original with no luck. I have replaced the fuel filter, with no luck(was hard to prime).

Truck runs perfect as far as my wife is concerned, as she never puts her foot down at all, and it will do a cross country trip with the cruise at 80 if I wanted to, but it’s just when you ask it for power, it delivers for a split second, then cuts your power back significantly.

I can order an ACDelco MAF sensor for around $350, but I wanted to get opinions before doing so, as money is right.

Thanks in advance, hope to get this figured out soon!

mitch
 

Mryan1789

New member
Mar 9, 2021
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Can you log it to see exactly what it’s doing? Could be a number of things
I don’t have any sort of scanner like that, and I don’t have much for diesel shops within 100 miles. Here are two pictures of the parameters that my cheap scanner will show. These are at idle:
 

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Mryan1789

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Mar 9, 2021
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Mryan1789

New member
Mar 9, 2021
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Any smoke at WOT?
Fr the first couple miles or five minutes, yes. Regardless of letting it warm up for 10+ min.

when I roll onto the throttle and the turbo spools, I’ve got a good, healthy 2-3 seconds of black smoke, BUT once it starts acting up, the smoke will come on for a split second then IMMEDIATELY stop once it cuts power and accelerates at half throttle even if the pedal is to the floor.
 

Budneeds2beers

Aka Mike Honcho....
Aug 25, 2016
497
4
18
Cali
So now you’re not getting any codes now, but when wot it will spool then cut out after a second?

check for a boost leak?
Its an lly, so whats are the vanes doing? Checked for a bad position sensor or sticking ring?
Whats your “tunner” saying? Did he flash it back to stock?
Did you look for any chafed/loose maf wires?
good luck with fixing.
 

Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
21,112
4,846
113
Phoenix Az
How did you tune the truck with EFI Live? if you have an autocal, you have the ability to log. the tuner can set it up.

if the WOT you show really is 100% and correct figures at WOT, your rail pressure is only 9700psi. FAR too low. if your tuner decided to turn off rail pressure codes instead of making the tune correctly, you will get "ghost limps" like you have now from too low of fuel pressure and have no idea why.

you need to get a proper log of this thing to know for sure.
 

Mryan1789

New member
Mar 9, 2021
8
0
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Since you did an get delete, I have a hunch that the oringed tube that goes into the mouthpiece has slid out under boost
I just did a block off plate and tuned it out.
I checked for boost leaks and didn’t find much of anything.

I replaced the fuel filter housing(noticed it wouldn’t prime when I changed the filter), and that helped a bit. While changing that, I noticed the lines going to and from the filter housing were EXTREMEMELY dry and crunchy. I replaced both of those as of tonight.

*what I’m guessing, is that it was sucking air into the system and losing fuel pressure there’s does that make sense to anyone else?