need tuning advice - 2008 Silverado Z71 with sloppy stage 2 cam

[Bgramling524]

this is what ive got. the vehicle is a 2008 Silverado z71 4x4. its a 5.3L (LY5) with 4L60E. I have installed a sloppy stage 2 camshaft, ls7 lifters, new pushrods, new .560 beehive springs. While the truck was on its stock tune AFTER cam install, it did start up and run, and was driveable. now i have HPtuners and ive been learning as i go, reading up on the forum and watching tutorial videos on youtube. ive made some adjustments to the tune, but i dont have a wideband yet so i really havent been able to see what im doing. anyway, now when i start the truck, it starts up but dies after a few seconds. when i pat the throttle to try to keep it going, it has hardly no throttle response and it seems like its cutting out like its out of fuel or something. ive attached my current tune file and a few logs to this post. i would greatly appriciate any help or advice.

[5FDP]

Give it more idle rpm when cold. No engine is going to be very happy with 700 rpm at cold starts. Look at how the stock file has it, it gets lower as rpm rises.

Also add a little bit of base running airflow because of the camshaft.

Return the dynamic airflow high rpm disable settings back to stock if you aren't running speed density.

Try 20 degrees of idle timing and lower the over/underspeed spark correction settings. You don't really want it to allow a -17 to +14 timing swing, try to +/- 8 degrees.

I can't view the logs but those are just some quick things I saw looking at it.

[Bgramling524]

Okay, thanks for the input. Ive updated the tune, would you mind going over it again? I should have mentioned that this truck is otherwise stock, besides for free flowing exhaust and an air intake. i have not loaded this tune into the truck yet, but i will in the morning. in the mean time hopefully i can get some more information from anyone who cares to share their knowledge.

[kevin87turbot]

That combo typically needs a little higher idle speed than you currently are targeting. I'd typically target 750-775 rpm. You'll need to add a little more min airflow as well. I would suggest changing the dynamic airflow settings to a smaller value, such as 200 for the high and 100 for low. That will allow you to run primarily on the MAF table.

I'd also recommend changing the valve springs to some PAC 1218 springs. It's very likely that you'll have problems with a spring designed for a maximum lift of 0.560" and a camshaft that has 0.585" lift.

[reubone]

basetunev2try.hpt
See if this is an improvement

[Bgramling524]

thanks for that. i have been having an issue with startup, like theres no throttle response. i loaded your version of the tune file though and recorded a little bit. basically the first half of the log is with my issue that ive been having. once it does whatever it does though and my throttle response is there, it seems to do great. ill get some more logs of some regular driving and highway driving though, and ill post them later. thank you for your update on my tune though!

[Josue Galban]

Hello friend, how are you doing with the truck? It has improved. If you want, write down my contact number. If you need help with something, I could help you.

logo quickstep.png

[reubone]

It looks like your having major issues with this vehicle. The fuel pressure is reading very low and the engine really seems to be struggling. Might need to back up and double check the soundness of the cam install and the recheck the fuel system. I would venture a guess and say that the cam is out of time. You have almost zero idle vacuum which shouldn't be happening.

[Bgramling524]

OK, the cam is installed 100% correctly. I have a new stock fuel pump that i need to install, so ill try to do that today to hopefully fix the low fuel pressure. I know i lined the timing marks up correctly when i installed the new cam. the engine does not struggle. only on startup, sometimes, i have an issue with it not wanting to stay running and theres no throttle response. I clear the codes and the issue is temporarily resolved. Could the low fuel pressure be the cause? I'll record another data log to post soon.

[reubone]

It is possible that your fueling issue is causing it to be weak. It should be way more responsive to wide open throttle inputs so start there I reckon.

[Bgramling524]

update... replaced intake manifold gaskets and seems to have improved. can anyone chime in?

[kevin87turbot]

You've got the incorrect calibration for your MAP sensor. That's why it looks like you have poor vacuum at idle and you have bad throttle response on startup.
The MAP should read atmospheric pressure with key on/engine off. Yours is reading 125 kPa.

Enter the MAP linear value of 128.20 and offset of -0.30 and it'll read properly for your later style MAP.

[Bgramling524]

Im guessing a bad MAP sensor would also cause this reading to be off? i have swapped MAP sensors with 2 others (dont know if they were actually good or not) and it still reads the same with the key on, engine off. ill get a new MAP sensor and see what happens then.

[mechanicalmatch]

I have run into a similar situation with an 8.1. it was reading about the same. There was a pushed back terminal on the sensor connector (harness side) due to a bent pin on the sensor. When the "faulty" sensor was replaced by customer, the problem was still there. It was fixed with a new terminal.
On my wife's 08 Tahoe, the plastic split loom that covers the harness has become brittle in multiple spots. It is possible that it is the same way on your and possible that the wire rubbed on something and when you moved it, the wire could have broke. Sometimes a simple careful tug test on each individual wire of the circuit will help find the issue.
I would take a good look at sensor calibration as well.

[Bustedknuckleperformance]

This was a massive help. Thank you. We had been struggling getting a smooth idle. Followed your suggestions and it runs great.

[Bgramling524]

Busted knuckles, if you need some of my revisions to try out I will gladly post them on here so you can give them a shot. I've got some much better revisions for the tune on this truck saved to my laptop. I will post them for you in the morning.

[Bgramling524]

bustedknuckles, compare these tune files to your current tune. hope it helps.