No Code Acceleration Hesitation - Any Ideas?

[StupidBmblB]

Has anyone else encountered a significant hesitation on acceleration without throwing any codes or misfires?

I have a new to me 2011 SS with the LS3 and about 116k miles on it, I bought it on a bit of an impulse (hence the screen name) so I don't really know too much about its history. It appears to be mostly stock outside of an aftermarket cold air intake.

The issue primarily happens once the car is warmed up, but occasionally even if cold. It is worst in 2nd gear but not exclusive to it. The one time I took it on the highway it was able to accelerate smoothly at speed for a little while (even when hesitating getting to speed) but eventually I could feel the same type of hesitation at speed as well.

I have a mechanic looking at the car now, and he identified that the APP signal was not matching the input, he replaced the pedal assembly with the sensors, but that did not fix the issue. Most of the other things he has looked at appear to be within the norms. I suppose a computer issue is possible, but that seems like a low probability type of problem from what I have read.

Here is what I know:
- No codes are presenting themselves
- No Check Engine light
- The APP sensors output is not matching the input
- New Plugs and Wires (plugs didn't show any signs of mechanical engine issues like carbon, oil, or fuel on them)
- New MAF sensor
- Throttle body looks clean
- Fuel Injector solenoids seem to be firing (I checked with Stethoscope)
- Fuel Pressure is good
- Tuning appears to be the stock tune

The one area I asked him to look at was the 5v reference data on the Accelerator Pedal for Ref1 and Ref2 to see if there might be anything in that data that helps show a potential electrical issue on one of those circuits. He had only looked at the gross output so far. I’d think a short or bad ground could cause bad output on one of the APP sensors, but I am basing that on reading and youtube videos. It seems on most of those though that a 5v reference error would cause one of the sensors to generate a code which isn’t happening for me.

Any ideas of where else to look/check? I was thinking maybe a vacuum leak, but not sure what areas would be most likely to cause this kind of problems. I am not a car guy, but I have learned a lot the past few weeks chasing this down, but I am relying on the mechanics that have looked at it so far to let me know what they are seeing.

I have really appreciated reading through the various posts with similar symptoms, but haven't found one that answered this particular problem yet. The symptoms feel very much like the misfire problems people get with the stabilitrak light, but those fixes don't seem to be the problems for me.

[acutron42]

I would run the fuel as close to empty as possible, fill it up with no ethanol premium & put in a bottle of K100. Without seeing any scan data it is hard to diagnose.

[Pkeen]

I read a post where someone installed an aftermarket MAF sensor and had the same issue, so he replaced it with a genuine gm part and issue was solved! Don't know if yours is aftermarket or not,just throwing this info out there!

[1JEWLDSSRS]

Originally Posted by Pkeen

I read a post where someone installed an aftermarket MAF sensor and had the same issue, so he replaced it with a genuine gm part and issue was solved! Don't know if yours is aftermarket or not,just throwing this info out there!

I too remember reading this on here. I think the aftermarket the person used was by a company called JET High Performance. It didn't worked and caused problems, until he switched back to OEM..

https://www.google.com/search?client...j0j15&ie=UTF-8

[StupidBmblB]

Originally Posted by 1JEWLDSSRS

I too remember reading this on here. I think the aftermarket the person used was by a company called JET High Performance. It didn't worked and caused problems, until he switched back to OEM..

https://www.google.com/search?client...j0j15&ie=UTF-8

Thanks for the info, the first thing I did was install an OEM MAF sensor, since I had seen similar posts where that fixed the problem. Unfortunately that didn’t do it.

I’ll have to look for no-ethanol fuel too, I ran a BG fuel treatment, but the hesitation is so bad it’s hard to put any miles on it to burn through the gas.

[1JEWLDSSRS]

Originally Posted by StupidBmblB

Thanks for the info, the first thing I did was install an OEM MAF sensor, since I had seen similar posts where that fixed the problem. Unfortunately that didn’t do it.

I’ll have to look for no-ethanol fuel too, I ran a BG fuel treatment, but the hesitation is so bad it’s hard to put any miles on it to burn through the gas.

Well that just bites the big one!!

[hesster]

116k miles, so she is well "broken in".
TB or Accel Pedal issues will usually always throw a code, and many times send you into limp mode.
If the O2 sensors are original, they are tired and can cause the issue.
Plugs gapped correctly?
You say TB is clean, no coaking where the plates interface with the TB housing bore?
Aftermarkert MAF sensors yielding improvement is a waste of $$.
Maybe do a Injector Leak down test.
If all else fails, get a HP Tuners MPVI3, datalog, and get a pro to tell you what the real issue is.

[gtstorey]

Might need to find out if any codes where turned off with HP Tuners to enable a quick sale. How did you determine the "Tuning appears to be the stock tune"?

[StupidBmblB]

Originally Posted by gtstorey

Might need to find out if any codes where turned off with HP Tuners to enable a quick sale. How did you determine the "Tuning appears to be the stock tune"?

I’m going off what the guy I have been working with tells me. So I am somewhat at his mercy. He went in thinking maybe someone had turned off various components (I’m speaking out my butt a little here with my understanding) but when he looked at the tuning data it seemed stock to him.

[StupidBmblB]

After some battery terminal clean up the data seems to be cleaned up quite a bit. The APP now appears pretty smooth, which makes sense why a new pedal didn’t change anything in how the car actually drives. We are thinking the problem is that the MAF is recording a significant drop in air flow which is then causing the engine to run lean as the fuel is reduced. The MAF sensor was the first thing I replaced, so I think next steps is to check out the harness and wiring to see if anything is there.

If anyone sees anything in the data that looks off, I’d be curious to hear any ideas!

I truly appreciate all the views to the thread and those that have responded.

[gtstorey]

You can add VE to the scanner in the same units as the MAF and compare and see if they are similar. Probably won't be since the MAP is consistent. You might want to add throttle body to the list to confirm it isn't closing to cause the MAF drop, but again MAP stays consistent.

I just would expect this to throw a MAF code if everything is still stock settings in the ECM.

[acutron42]

Is it possible for you to get pics of all the channel data on the left side of the screen?

[gtstorey]

Originally Posted by acutron42

Is it possible for you to get pics of all the channel data on the left side of the screen?

Or add the HPT log.

[FasNuf]

Thats a lot of knock!