06 Sierra with 5.3 low on power

[Rags]

The problem is there is no power on take off .. I can stand on it and it just takes off gradually until the RPM's get over about 2,000 then seems to run ok. When pulling my boat ( approx 3,500lbs ) it starts dieing when i come to a hill then drops to 2nd and runs great at 3,500 RPM's untill it shifts.

I hooked a scanner to it to read data and everything seems ok EXCEPT at an idle the ignition timing showes 18 deg, .. but when i hit the gas it drops to -2 deg for a sec and under load drops some but not as much. THERE IS NO CHECK ENGINE LIGHT ON.

I took it to the local dealer and they confirmed my drivability problem and they said they checked everything, even fuel pressure and everything seems ok except the LOW power on take off. They said they reflashed the computer but it does the same thing and since there is no check engine light on they have no clue what is causing it. My gas milage is also about 11 MPG

I have heard these trucks are equipped with " Torque Management" that lowers the power on take off and can be turned off by a dealer. BUT the dealers around here have never heard of it.

Sorry such a long post but i'm getting frustrated. PLEASE if anyone can help point me in the right direction here i would appriciate it.

Thanks

 

[Molson02536]

The problem is there is no power on take off .. I can stand on it and it just takes off gradually until the RPM's get over about 2,000 then seems to run ok. When pulling my boat ( approx 3,500lbs ) it starts dieing when i come to a hill then drops to 2nd and runs great at 3,500 RPM's untill it shifts.

I hooked a scanner to it to read data and everything seems ok EXCEPT at an idle the ignition timing showes 18 deg, .. but when i hit the gas it drops to -2 deg for a sec and under load drops some but not as much. THERE IS NO CHECK ENGINE LIGHT ON.

I took it to the local dealer and they confirmed my drivability problem and they said they checked everything, even fuel pressure and everything seems ok except the LOW power on take off. They said they reflashed the computer but it does the same thing and since there is no check engine light on they have no clue what is causing it. My gas milage is also about 11 MPG

I have heard these trucks are equipped with " Torque Management" that lowers the power on take off and can be turned off by a dealer. BUT the dealers around here have never heard of it.

Sorry such a long post but i'm getting frustrated. PLEASE if anyone can help point me in the right direction here i would appriciate it.

Thanks

You are correct about the Torque Management, It's been around since 1996 and got better in 2003 with the drive by wire system like what you have. Most of the guys have there PCM reprogrammed buy Dyno Tuning it, but that get's expensive. I have HP tuner and play with my PCM for the most part of the year on my Jimmy and my dad's Yukon, and yes i have turned the Torque Management down to 8% on the Yukon. >> Don't trust the old man's right foot any more, would like to get his Yukon in the future.

Here is a link to where you can get your PCM reprogramed to wake up your 5.3 Liter Vortec which is what's in the Yukon. http://www.pcmforless.com/ give them a call and they will be more then happy to answer any questions you have. Food for though, also find a place that has a tech2 Scanner to inspect your throttle peddle out put readings.

 

[Rags]

Thanks Molson, I knew i was on the right track just can't get the dealers to listen to me. Although i was going to look into a programmer to help with the power instead of sending the computer out. Can anyone suggest a good programmer that would take care of all issues, even torque Management?

 

[Rags]

Thanks Molson, I thought i was on the right track but just can't get through to them. I was thinking a programmer if it would do everything i needed. I can't do without the truck for any period of time.

If anyone can suggest a programmer that would WAKE this thing up! let me know.

I have already put cat back exhaust with flowmaster and dual pipes.

 

[Rags]

Thanks Molson, I thought i was on the right track but these dealers won't even research it. Would a power programmer do what i need to WAKE this thing up?

If anyone knows of one please let me know!

Thanks

 

[Molson02536]

Thanks Molson, I thought i was on the right track but these dealers won't even research it. Would a power programmer do what i need to WAKE this thing up?

If anyone knows of one please let me know!

Thanks

Was your Sierra always like this when you got it from day one??? See if there is a update program that GM has in there TSB. There always updating there PCM programs every year to improve the engine and transmission's performance.

For now try this and post back to us. This seems to be a very common problem with the 4.8's & 5.3's, If you have a dirty or bad MAF (mass air flow) sensor and fuel calculations depend heavily on the MAF signal when warmed up (closed loop), the PCM is reading off the O2 sensors and makes the Air fuel ratio calculations for the injection pulse duration and timing. Long story short, try Cleaning your MAF sensor.

If that does not work, My suggestion would be to take it to a tuner that knows vortec/LS motors.

First thing as mentioned, would be to scan the PCM for diagnostic trouble codes. If no codes, it could still possibly be an intermittant sensor problem. I would check the MAF sensor first. Unplug the MAF start it and see if it still stumbles on throttle tip-in.

If not the MAF, I would check the IAC next.... what's the IAC counts at idle? Typical for an auto trans in park would be 10-30 steps.

What's the MAP read?... should be about 45 kpa at idle... Check the TPS, IAT, TPS, ECT.... check all the sensors. Once the motor is at temp, See if the PCM is going into closed loop and adjusting the fuel trims.

If still nothing obvious, it most likely just needs to be tuned. My advice is unless you're really an expert at tuning, take it to a professional tuner. He can put it on the dyno and log everything going on in the PCM and see exactly what needs to be adjusted. Getting the right Air/fuel ratio is so critical. Too rich and it runs like the way it is now, too lean and you can get detonation and not a good thing ever.

There are over a hundred tables used to arrive at the right calibration or tune in a stock GM PCM. An engine that stumbles at throttle tip-in could be caused by a number of things, but absent an obvious bad sensor and it's usually the result of a problem with the VE table. Getting the VE right is key to a good running engine with crisp throttle response.

It may cost a couple bucks to take to a good tuner, but it's worth it every penny. Call the guys at http://www.pcmforless.com/ and explain to them the issues your having and they will be mor then happy to help you out and you can have your PCM tuned buy them for a great price for what your 5.3 vortec can do after they have tuned it.

P.S a power programmer will not fix this issue, they still have limitations. I have a http://www.hptuners.com/products/vcmsuite.php which can do the job, but expensive and only good for the tuner junkies like me