Intermittent throttle issue...

[Whiteboyz71]

Hello, new here and this is my first post.

I have a 2007 (NNBS) Silverado CC Z71 5.3L and recently had problems with it's AFM system. It droppped the #7 cylinder due to a seized intake lifter. I decided to go with an AFM/DOD delete kit from Brian Tooley Racing and his Stage 1 cam, Long tube headers/cat delete & single 3" exhaust. I had the work & tuning done by a local well known private mechanic here in the 405 and the truck runs great now, but i've been dealing with an intermittent throttle loss issue for about a month and a half now. My guy told me it never did it the few times he drove/tuned it, it started a week or so after getting it back. We tried catching it in the act and did, the tps monitor on his computer wasn't responding when it does this. I've replaced the thottle body TPS sensor, throttle pedal TPS sensor assembly and cleaned the MAF sensor and throttle body, but the problem still persists. You can put it in drive and it'll pull itself down the road but there's no response when pressing the throttle pedal and picks back up a few seconds after not trying to give it throttle. Usually does it every morning, after work when it has sat a while and any other time in between when it decides to act up. Also, there are no warning lights when it does this.

Thanks, Mark

[HackAbuse]

Had a customer with a really quirky similar issue. It would happen to him occasionally when accelerating away from red lights. He ended up having a catastrophic failure while just driving normally around town. He had a new engine installed but we wont get the opportunity to test it until spring.

[GHuggins]

Check fuel pressure and then look at the tune and make sure he hasn't messed with the throttle driver demand tables...

[IARLLC]

Just curious if there have been any codes to go with it. These things are pretty sensitive to errors in the pedal sensor or tb sensor. Also these do a fare bit of babysitting (taking your pedal input and deciding how much throttle to let you have). Torque Management on the engine or trans side can decide not to give you what you want for various reasons. GEN4 and GEN5 have a number of speed/throttle limiters that come into play with various errors that are not necessarily drivetrain codes that would be displayed by a generic scanner. Transfer case codes, traction control, to name a few. I have seen erratic rear wheel speed sensors mess with traction control/stability function. Maybe a conflict between MAF/SD tables that would not be caught if you have P0101,P0102,P0103 turned off.

How long does the issue usually last? Do you have to shut it down and restart it to get the throttle to respond to the pedal or just an intermittent lack of response?

[Whiteboyz71]

I'm no tuner by any means, just looking for answers and get it responding like it should. But I will relay this info to my guy.

It's just intermittent & usually lasts about 10 to 15 seconds or less, but has done it to me twice on the highway and lasted for what seemed about a mile or so. Even if I floor it, rpms creep and it doesn't want to go any where. I've tried stopping and turning it off, but that doesn't make any difference in trying to clear it up.

The throttle driver demand tables were not changed, I remember him telling me he never changes those tables cause it can cause permanent PCM failure.

[Whiteboyz71]

Found a thread where similar symptoms were happening with a 2007.5 4.8L automatic and turned out his throttle follower torque was off, returned to stock and all was good. I'll be going to my mechanic/tuner Friday afternoon and will mention this to him and go from there.

[IARLLC]

Good job. Good luck

[Whiteboyz71]

Good job. Good luck

The thread I found, he mentioned it would loose throttle before trying to shift into 2nd gear, then would pick back up once returning to idle. He even replaced the throttle pedal TPS assembly & throttle body TPS sensor as I've tried the samething. I tested his description this morning while pulling out the drive way and it did what he described, throttle loss before shifting into 2nd and picked back up once it returned to idle. I sure hope we get somewhere with it Friday...

[Whiteboyz71]

Thought I'd update with good news, throttle is back to normal.

Finally met up with my tuner last week and here's the changes he made after me telling him what I found here and that's what he checked/changed.

His changes:

I set the following table back to stock. They were maxed out.

Engine - Torque Management- ETC tip in torque limit

[GHuggins]

^^^ That's not the throttle follower table - that's the tip in torque limiting tables

[STR8BALLN]

If the ETC-tip in tq management is set to disable, the ECM should not reference this table right?

[Whiteboyz71]

^^^ That's not the throttle follower table - that's the tip in torque limiting tables

Like I said, I'm no tuner by any means. I simply relayed info I found here to give him an idea of where to start. I had a feeling it would be something simple and his changes fixed my intermittent throttle issue...

[Higgs Boson]

I have also found an issue with the ETC TM table. GenIII stuff you could max it at 100 across the whole table. GenIV stuff it is best left stock, even though it is not in the electronic throttle tab.

[GHuggins]

I leave the tables themselves stock, disable via switches and set rate to 100 - I don't mess with any of the individual tables? Interesting - maybe just maxing them out is causing the problem?

[Higgs Boson]

i dont think they all have switches