Engine won't climb RPM

[ns158sl]

My truck won't climb RPM and pretty much falls on its face after a certain point. Seems to be around the 5000 RPM area with some boost. I already regapped my plugs down to .022". It is a 383 5.3 with 317 heads. 212/212 .560/.560 112 cam. gt5002 turbo. 5 inch exhaust. It almost feels/sounds like fuel cut, but the tune says otherwise. Fuel pressure was steady also. If you look at the frames between 2:20.21 to 2:20.28, it is pretty noticeable of WOT and watching the RPM ramp up pretty decent and then kind of plateau, all while be WOT.

Eric

[Nastruck]

I didn't look at the tune cause I'm walking out the door but main thing see in the log that's stands out first hand is your Long term fuel trims are carrying over into boost adding 10% on one side and 4% on the other. For me pump gas 11:1 is pretty rich compared to what I normally run and with such low IATs you could try adding a little ignition timing to see if it helps.

[GHuggins]

Also wondering if you don't have weak valve springs and/or too much preload causing valve float? Then you need to open the plugs back up to around .032 too...

[ns158sl]

I guess it could,be, the weird part is the engine ran fine before i added a bigger fuel pump and intercooler. It has ls6/3 springs.

[ns158sl]

So I took the truck out again, without a charge pipe on to rule out boost related. The truck still acts the exact same way as before. I logged a bunch more random PIDS to see if I see anything weird. I guess the only thing I did notice is the cam hi to lo locks up about right where the rpm ramp starts to taper off. Any Ideas on what that is all about?

[ns158sl]

Well I installed new valve springs. I would post a log but it acts identical to the log I already posted. Is there something stupid obvious I am missing? This had taking me for a loop, and the bad part is snow is flying now.

Eric

[5FDP]

A shot in the dark here, flash back to a old tune that you know it good. Like something you did a month or two ago, take that tune and make any changes to it that are on your current file and flash it in. Maybe something is just wrong with the most recent file you flashed.

[ns158sl]

I have been meaning to try a write entire from an old tune and see what happens. If the roads are still dry tomorrow I'll give it a shot and report back. Thanks!

Eric

[ns158sl]

Well it was warm enough out, so I did a write entire from a file from 2013. Still exact same thing. I'm starting to wonder about cam and crank sensors? I really feel they would set a fault if it was one of those or even wiring related to those. I did have a friend with a sentra running an AEM Infinity ECM with about the same issue and it was a cam sensor without setting a fault, but that was a full aftermarket system so maybe that isn't even relatable.

Eric

[ns158sl]

Bringing this back from the dead, because its spring and the Truck still isn't fixed haha. So no I am just trying it in Park. It seems like the truck can handle around 5500 RPM. I tried lowering the rev limiter down to 5500 cut and 5400 resume. In park it seemed to be fine. Didn't try driving it. I raised the Cut and Resume to 6200 and 6100, and now the same thing happens like the truck isn't allowed to rev past 5500.

[5FDP]

Why are you even trying to rev it to the moon in park?

Also you lost the IAT sensor in that last log, something to look into.

[ns158sl]

Trying to make the neighbors mad obviously! Haha. No I was trying to see if it was different in park/neutral or more of a powertrain deal. Totally missed the iat! Tomorrow is another day.

Thanks again
Eric

[ns158sl]

The only other odd things I finally noticed is dynamic airflow pegs at 512 the exact time the truck feels like a dog. The other thing is the delivered engine torque also pegs 540 ft lbs. Is there something I am missing with those? The engine should be in straight SD.

Eric

[lukearmstrong1990]

given youre only running 10psi I would suggest trying to come back to 11.7-11.9 AFR under noise.

I would max out the P0121 ans P0106 values in engine diagnostics in airflow. however these would normally log a DTC if coming into play.

given its with RPM under boost I would suspect valve float from weak valve springs as the most likely cause

[ns158sl]

To be honest, I'm starting to wonder if it is too rich to even climb RPM. Everything was fine and ran good before I changed the fuel system. Same thing with the valve springs. They were fine and it revved to wherever I wanted it to. I thought maybe they got weak from sitting for over a year so I changed them last November. Tomorrow I am gunna start leaning it out and see if it responds. I guess I don't know how rich is too rich for a engine to get fuel logged, hah.

Eric

[5FDP]

A wideband would tell you what the fueling is like and if the data is correct from the previous log you have a rather large fueling error between the commanded AFR and the actual AFR.

[ns158sl]

of course I am running a wb. its an lc1. ill lean it down tomorrow and see what happens.

Eric

[ns158sl]

So I tried taking a lot out of the VE table and low and behold the truck hits rev limit. I took it for a quick spin down the road and it actually climbs rpm. I already ran out of time today to keep playing with it but I think maybe it was just overfueling. I would of never though 10 to 11 to 1 especially with boost would make it too rich to build rpm? Either way I think it might be fixed!

Thanks everyone!
Eric

[5FDP]

Maybe your wideband is lying to you and it's richer than it says it is.

I wouldn't call it fixed fixed but it's better, the VE still needs to be cleaned up.

[ns158sl]

Well I was wondering the same thing about the wideband. Maybe time to invest in a better one or atleast just change the sensor. I know the VE is terrible. This current tune is just a really old tune to see if it would run different. Thanks again!