LQ4 T-56 DBW, engine wont rev past 1500 rpm (ish) abuse mode adjusted (they said)

[QUA-HOON]

I could use some help. My g-body monte carlo is about finished up. 2006 Lq4 (engine and PCM), t-56, DBW set up, everything else is stock besides the transmission change, a Racetronics fuel pump and hot wire kit. I replaced the TAC module, APP to TAC wire and the APP sensor on the pedal. Engine harness is from PSI and unmodified as is the APP to TAC wiring.

https://youtu.be/KWUmS2cQvT4

Simply put, the car won't rev past 1500-1600 RPM. At that point it sounds like a fuel cut off happens and the engine revs up and down, no higher than 1500 -1600 rpm. I read that "abuse mode" is likely the cause and needs to be tuned out, so I brought the PCM to KC Maxx Performance, and I'm now out 200 dollars and the engine still does the same thing.

Does anyone have an idea on whats up with this thing? I'd like to start driving this soon. If I can correct this through HP Tuners, I'm probably biting the bullet and buying that as soon as possible. I just need my car to not be a paperweight / parking lot land speed record holder.

Alex

[2xLS1]

Sounds more like Reduced Engine Power. Perhaps a mismatch in the pedal/TAC/TB/PCM year OS.

[QUA-HOON]

The engine, pcm, pedal, TAC, was a complete pull out from a 2006 trailblazer. The engine had no pedal response on first start, trouble shot it to be a bad TAC module. Purchased another for a vortec motor and now this. I replaced the app sensor with a Dorman unit (but it does the same with the original one ) and the app to TAC module wiring is new frim PSI.

[someblackguy224]

Hey,

Free bump, you dont see this often. This is a shot in the dark but is the throttle body opening fully? or do you have a helper to so that you can look over the engine for any irregularities while they press the throttle? I believe buying HP tuners is the first step lol ERM Performence is who i just brought my HP Tuners Pro Package from it comes with a tuners guide and tutorial. WELL WORTH THE MONEY FOR SURE!!

How ROAD READY is this set up? what other codes are you getting? i watched the video could not tell if the TPS Percent increased CHECK ALL GROUNDS!

[2xLS1]

I could use some help. My g-body monte carlo is about finished up. 2006 Lq4 (engine and PCM), t-56, DBW set up, everything else is stock besides the transmission change, a Racetronics fuel pump and hot wire kit. I replaced the TAC module, APP to TAC wire and the APP sensor on the pedal. Engine harness is from PSI and unmodified as is the APP to TAC wiring.

https://youtu.be/KWUmS2cQvT4

Simply put, the car won't rev past 1500-1600 RPM. At that point it sounds like a fuel cut off happens and the engine revs up and down, no higher than 1500 -1600 rpm. I read that "abuse mode" is likely the cause and needs to be tuned out, so I brought the PCM to KC Maxx Performance, and I'm now out 200 dollars and the engine still does the same thing.

Does anyone have an idea on whats up with this thing? I'd like to start driving this soon. If I can correct this through HP Tuners, I'm probably biting the bullet and buying that as soon as possible. I just need my car to not be a paperweight / parking lot land speed record holder.

Alex

The engine, pcm, pedal, TAC, was a complete pull out from a 2006 trailblazer. The engine had no pedal response on first start, trouble shot it to be a bad TAC module. Purchased another for a vortec motor and now this. I replaced the app sensor with a Dorman unit (but it does the same with the original one ) and the app to TAC module wiring is new frim PSI.

Well something isn't adding up. A 06 Trailblazer was never equipped with a LQ4. I still say you have a mismatch of parts causing REP.

[someblackguy224]

Well something isn't adding up. A 06 Trailblazer was never equipped with a LQ4. I still say you have a mismatch of parts causing REP.

too an extent i agree, i think the question becomes very simply, is throttle by cable or wire?

[QUA-HOON]

Well something isn't adding up. A 06 Trailblazer was never equipped with a LQ4. I still say you have a mismatch of parts causing REP.

Well this info made me dig a bit. I don't know why I've been saying Trailblazer for this long. Ok The 8th digit on the PCM was a "U" which shows as LQ4, the block is stamped with a "6.0" and is iron. And luckily ebay keeps pretty good record and says the engine is from a 03-07 Silverado.. so not a Trailblazer. The year range kind sucks but I'll assume this is still a complete pullout from one truck, just me messing up the model. Thanks for getting me to correct that. So does this new info help at all?

Alex

[QUA-HOON]

The set up is drive by wire. New APP sensor, new app to TAC wire from PSI, and new (used) TAC module from PSI as well for a vortec truck.

https://www.psiconversion.com/produc.../ACC-1011.html

I tested the throttle body as well and it tested good per this guide.
http://easyautodiagnostics.com/gm/4....hrottle-body-1

Alex

[2xLS1]

Not all 03-07 ETCs, TACs and pedals are the same. Mixing the wrong ones will cause REP. One of my customers swore he had everything from an 05 Silverado in a transplant. Turned out all his ETC components were from an 06. Trying to run it with a 05 OS caused REP whenever you would try and open the throttle. Changing his OS to one from a 06 PU solved the problem.

[2xLS1]

too an extent i agree, i think the question becomes very simply, is throttle by cable or wire?

There is no REP on cable TB OS. REP is a fail safe mode for ETCs.

[QUA-HOON]

I guess how do I know what year my stuff is then so i don't waste credits? I honestly can't believe that a vortec pedal from the same year group wouldn't work with another. One year only parts, seriously?

[5FDP]

You could verify computer OS/year. Then use the part numbers off of the parts you have and see if they match for parts used with what year computer you have.

GM did tons of year only or two year runs and model only parts on many vehicles.

Without actually seeing data logs or files this is just an assumption of the problem. Maybe the place you took it too didn't even change the correct parameters to prevent limp mode.

[QUA-HOON]

You could verify computer OS/year. Then use the part numbers off of the parts you have and see if they match for parts used with what year computer you have.

GM did tons of year only or two year runs and model only parts on many vehicles.

Without actually seeing data logs or files this is just an assumption of the problem. Maybe the place you took it too didn't even change the correct parameters to prevent limp mode.

Hmmm thanks for the info about the parts. Seems like I am stuck until I can pull data. I bit the bullet and purchased HP Tuners tonight and it should be here on Friday. So hopefully then I can pull some data to better troubleshoot all of this. Thanks for the help so far. It seems like this will be on pause until Friday though. Until then, I'll be trying to learn the basics of the software and tuning through video and reading. Hopefully I can communicate this well to everyone to help solve this problem.

Alex

[QUA-HOON]

Got HP Tuners in on Friday.. Saturday after watching some videos and getting familiar with HP Tuners I was ready. I literally paid my near 200.00 to that shop for them to click abuse mode "disabled" under the Transmission Tab... and then forget to do anything else regarding the "won't rev past 1500 rpm" problem.

Under "Engine", "Torque management", "Abuse", there was the problem. It was still set to 1600 RPM. I changed it to 6,500 rpm, wrote it to the PCM, and started the car. Magic it revs. Car drove around the block just fine. Throttle is as a little touchy but maybe I need to get used to it and or figure out some things in tuning. But I no longer have a static display of a car in my garage anymore.

Alex

[5FDP]

Drive by wire cars from that generation can feel a little bit touchy if you've never driven them before.