Another head scratcher in the shop this week - low power

[webb06]

Customer came in wanted headstuds put in. I hooked up the computer and went for a drive to monitor EOT vs. ECT. Truck had almost no power. Driving 60 and mash the pedal and it wouldn't do much. Boost would be 20-21 psi. Oil cooler was bad so I did a few flushes on it and proceeded to pull the cab thinking the low power was from a sticky turbo.

Long story short everything is back together and it's still low power on top end. I've swapped a different turbo on it, PCM, icp sensor.

Truck has an sct tuner on it as well. Weird thing is when it's acting up, you can pull over shut the engine off, start it back up and immediately have normal power and everything runs fine. Within 2-3 hard pulls it acts back up. Shut if off its fine again for just a few minutes.

A little data....
When acting up under WOT icp is 3400, and that's what it's desiring. Ipr% is 70-71.
When it's running right under wot icp is 3400 but its desiring 3900. And ipr% is 85%.

Another thing is that the instrument cluster is all fudged up. Tach is reading about 200rpm low. Speedo doesn't work. Abs light on but no abs codes. Odometer hasn't moved since I've put about 30 miles on it.

Anybody have any idea what's going on? I've got IDS so I can monitor and get any needed data. Thanks

 

[Gary]

I'll throw out a couple thoughts,
Whats going on with exhaust back pressure?, is the tube clear? switch clean inside?
Then check MAP.
Will your scanner control VGT? try and work the VGT and see if the PID's change.
Maybe watch fuel pressure.
I'd look at that stuff.

 

[Gary]

Also check your MAF, I've never seen one go bad on a 6.0, but a gas engine will fall on it's face and sometimes not start when it fails.

 

[dieseljosh07]

What year is the truck?

 

[webb06]

I'll throw out a couple thoughts,
Whats going on with exhaust back pressure?, is the tube clear? switch clean inside?
Then check MAP.
Will your scanner control VGT? try and work the VGT and see if the PID's change.
Maybe watch fuel pressure.
I'd look at that stuff.

Exhaust back pressure is exactly what is being desired. I can control vgt and give it more boost and it doesn't affect anything. EBP, map, and baro are all the same. Swapped a maf sensor with no change it reads 32-36 at idle. Fuel pressure is 60-61 at all times. Turbo was cleaned before installed so was the replacement.

Truck is a build date 04/06

 

[hiniker88]

Stock exhaust? Cat plugged/bad?

 

[Mdub707]

Are you reading ICP with the tune on, or on stock tuning? How does it do with stock tuning? Any smoke when you're WOT and it's sluggish?

 

[webb06]

Stock exhaust but unhooked at the connection before the cat. Reading icp with tuner in. I've heard it affects the reading. Stock tuning it acts up every time. No smoke at all

 

[Mdub707]

The tune can certainly throw ICP readings off, I believe they usually read about half though. It may be worth trying to get the ICP readings on stock tuning though, just for a comparison. How is battery voltage when running and FICM voltage as well?

 

[webb06]

We went and drove another truck this morning and monitored the data. Everything is right in touch with everything the other truck is doing when it's running right for a little bit. Haven't monitored either of those

 

[webb06]

Sitting at an idle B+ is at 14.30 FICM is 48.5

 

[motleycrew]

man, it's a long shot, but I had a truck that was doing something similar to that, only it was bone stock.
Turns out, the cust. had put a fuel filter in it, and it was screwed up on the bottom of the filter itself. It wasn't pushing down the little sleeve in the canister all the way, which was chokin it for fuel on a higher RPM pull.
It would start to chug and die, so I would wait a second, cycle the key, (which refilled the canister), then fire it up and good to go.....until I floored it, or put it under a decent load.
Most filters have that "toothed" edge on the bottom of them to engage that sleeve and push it down. This one didn't, it was just flat on the bottom. TOok me FOR-EV-VER to find it, I kept checking fuel pressure pre-filter and it was fine....

Long shot, but check it out. This filter was from NAPA.
mike

 

[webb06]

man, it's a long shot, but I had a truck that was doing something similar to that, only it was bone stock.
Turns out, the cust. had put a fuel filter in it, and it was screwed up on the bottom of the filter itself. It wasn't pushing down the little sleeve in the canister all the way, which was chokin it for fuel on a higher RPM pull.
It would start to chug and die, so I would wait a second, cycle the key, (which refilled the canister), then fire it up and good to go.....until I floored it, or put it under a decent load.
Most filters have that "toothed" edge on the bottom of them to engage that sleeve and push it down. This one didn't, it was just flat on the bottom. TOok me FOR-EV-VER to find it, I kept checking fuel pressure pre-filter and it was fine....

Long shot, but check it out. This filter was from NAPA.
mike

I just installed new racor filters in it just before dropping the cab, but I will pull the secondary filter just to check it out.

Thanks for throwing out ideas

 

[webb06]

GOT IT FELLAS!!!

My dad took over the troubleshooting since I had another cab to get pulled. He wanted to start with the obviously things that were wrong, the instrument cluster was first on the list. There were "U" codes for the abs module and instrument cluster, so he began with a wiring schematic and found that 2 fuses in the engine compartment fuse box that should always be hot were not. These supplied power to the abs module. Found the contacts inside the fuse box burnt up. After repairing those and going for a test drive everything on the instrument cluster worked and it ran like a normal tuned truck.

Hope this can help someone down the road if they ever run in to this problem. Thanks again to anyone who threw ideas out.

 

['94IDITurbo7.3]

So why did burned up fuse contacts for the ABS module mess up the rest of the truck? is it just because it is all on the CAN BUS so everything is inter-twined so to speak?

 

[DEEZUZ]

Lol. Ok

 

[webb06]

Lol. Ok

what is the point of your post?

 

[webb06]

So why did burned up fuse contacts for the ABS module mess up the rest of the truck? is it just because it is all on the CAN BUS so everything is inter-twined so to speak?

no clue. i know that it solved the problem though. it fixed the instrument cluster and the driving issue. i dont have any explanation on how or why. just like many freak 6.0 problems