LS3 Need LS Guru help

[Timberline]

Hi all,

I have an LS3 525 crate motor all GM electronics, 6spd manual.

My issue is when cruising at a light throttle when it gets to 3500rpm the car jumps comes alive almost like hitting nitrous. It’s as if it is at 50% horsepower the 3500 boost adds another 50% horsepower.

I have taken it to to someone that works on these every day to have things looked at pulled intake and went all the way through the car bumper to bumper. Ran the computer while driving to check things out and adjust the tune the 3500rpm boost went away. Months later the 3500 boost is back.

any ideas?


thanks in advance. Jeff

[btmatt]

DBW throttle?

[robbbc]

Could be several things really. No real way to tell without looking at the tune. Are you using HP Tuners? Would be great if you could post the tune and a log. Possible that its a little on the lean side until Power Enrichment kicks in and you are feeling it; Spark tables wacky, or throttle related. What ECM do you have controlling your engine? Where/who did the initial tune?

[Timberline]

Thank You will have to check and see if I can get the the “fixed” tune. My guy no longer does the work anymore but I am sure I can get a copy of tune run.

[Timberline]

Sorry I am old school this new LS stuff ca. be Greek to me 🙂…. What is DBW Throttle.

[Timberline]

Sorry I am old school this new LS stuff ca. be Greek to me 🙂…. What is DBW Throttle.

[68Formula]

Drive By Wire... Electronically controlled throttle body.

[Timberline]

Thanks and yes DBW

[btmatt]

check opening ramp on throttle body. many times the opening is delayed and act as described.

also check fuel and timing tables to make sure there is no funny stuff there. also log to see if you are experiencing knock that would retard timing

[Timberline]

btmatt

Thank You will look into this it makes sense.

[streetk14]

So when you’re cruising at very light load, it feels like the throttle opens on its own? If the throttle body has a problem, it should throw a check engine light and some fault codes. I believe the ECU will go into a reduced power mode as well. There’s redundant sensors in the pedal module and throttle body for this very reason. Doesn’t really sound like that’s happening.

It could be a tuning issue I suppose. There’s a lot you can screw up if you don’t really know what you’re doing, and there’s a lot of “pro” tuners that are anything but. Did this setup get tuned by someone after install, or were you using the GM supplied calibration?

If you can get that tune file, I’ll have a look.

[Timberline]

streetk14
This issue has been since the start. It is all GM out of the box crate motor. When under light throttle light acceleration slowly climbing to 3500 …when it hits 3500 the car comes to life. Yes there is a check engine light. Will have this read and follow back up.
I will try to get the tune and I do know there are some that say they are great tuners and others that are great tuners which is also why I wanted to reach out.

[Timberline]

Ago
streetk14
So when you’re cruising at very light load, it feels like the throttle opens on its own? If the throttle body has a problem, it should throw a check engine light and some fault codes. I believe the ECU will go into a reduced power mode as well. There’s redundant sensors in the pedal module and throttle body for this very reason. Doesn’t really sound like that’s happening.

Ago
streetk14 -
this is exactly what is happening. Feels like the throttle opens on its own.
I have had the car drop into reduced power as well. But has not done that as of late
I have actually left the car idling in the drive way and it has as jumped from reduced power to full regular power as you could hear the power jump and the idle was just a little bit louder.

[robbbc]

Too much airflow can give a cruise control type of feel. Possible that there is not enough base running airflow until you hit higher rpm? Again, without looking at a log or tune; it is just speculation. Fuel multipliers are at play based on engine coolant temp, intake air temp etc. Spark tables add or subtract due to engine coolant temp, intake air temp etc; so its going to be tough to pinpoint what the issue is without having that data on hand. Even the intake valve temp comes into play as to if it will add or subtract fuel. That could be why it changed sound while at idle.

[streetk14]

I agree, but this was a stock GM tune file that was supplied with the crate motor. While my experience has been that those tunes aren’t great (no VE tuning, stock spark table, etc.), it shouldn’t be doing that. I think the check engine light and reduced engine power mode are the key here.

[robbbc]

Agreed, streetk14. Sounds like there is an issue with the throttle settings. Not sure how i missed the engine light and REP mode. lol