2005, Z-51, 6speed, 22k miles
Driving the other day, I used full throttle on entry ramp (3rd gear) but not high rpm's, up-shifted and thought I noticed that the rpm's increased abnormally between shifts, like when you miss a shift. Figured it was my imagination. Then it happened again, not my imagination.
Later on return trip it happened again, this time also after brief full throttle but the up-shift did not cancel it. Took it out of gear, engine was racing, (thank you Chevy for the rev limiter !!!) shut it off and pulled over. Restarted & the engine still raced. Shut it off, repeated restart 2 more times, engine still at full throttle. When shutting down, the engine shook/vibrated a little strangely when near zero rpm's. Finally, I opened and shut the door, restarted and all seemed normal. (can't imagine that there is a connection with the door). Obviously I am more than a little nervous about the next time I put my foot to the floor!
Has anyone out there had this happen with the 2005 LS2 or similar??
Any suggestions before I take it to the dealer for what might be expensive guesswork??
Thanks !

 

IS the car stock? Any modifications?


Elmer

 

Pretty sure it is Stock. I am 2nd owner, have had it 2+ years. Never happened before.
Thanks for your interest.

 

I believe you have a wireless throttlebody. I'd just do the dealer thing. If you can read any codes that might be stored, before you go, the codes can be checked for some direction on the repair.

Elmer

 

LS2 engines had problems with gas pedals. I would start by cleaning the t-body and check the throttle blade for "binding". it is early in MILES but the throttle actuator may be going bad. check 1 thing at a time.

good luck.

any chance the floor mat or plastic cover over your pedal box is causing the problem ?

 

GM Goes thru GREAT PAINS and are over cautious when it comes to throttle problems. If there is any error between the the actual throttle blade position and or the throttle peddle it will go into reduced engine power mode.

However,,, IF,, your throttle peddle some how is sticking at FULL or partial full throttle, the engine and ECU do not know the difference between a lead foot or stuck peddle.

Make sure that the actual throttle peddle is not bound up because of carpet or some sort of mechanical issue.

If you let off the throttle and the Throttle body remained full open, the engine would have or SHOULD HAVE shut down.

So,, IMHO, you have some sort of Accelerator Position Sensor issue. Thats where I would check first.

You can turn the IGNITION SWITCH to ON with out starting the engine and remove the air-bridge and if you operate the accelerator peddle, you can have someone observe the throttle blade. They should operate very smoothly and quietly and follow the peddle position exactly. While you have the air bridge off, its a great idea to clean the TB and MAF

Look for something that could Bind the throttle peddle.-

Bill

 

Thanks to all for the replies. I do have (did have) a 2nd floor mat on top of the factory mat. It is heavy rubber but of course not hooked down. I just checked it, do not see how it could possibly get in the way, no other possible obstructions. Pedal has plenty of return spring. I don't think obstruction of pedal was the cause. Removed 2nd mat, test drove and could not duplicate the issue (this time). Will look into throttle body and all of everyone's suggestions as soon as I get the chance (and the heat wave here dissipates). Thanks to all!!!

 

can't be a coincidence that it sticks when at full throttle -- I'd think an internal problem in the electronic throttle...even though the pedal returns, the electronics might not be reading it.

 

Like I stated previously, the throttle position sensor and the accelerator position sensor have TWO equal and opposite sensor voltages.

When the throttle is shut, one phase is at max voltage (5 VDC ) and the other phase is at minimum (0 VDC)

As the throttle opens, the voltages on each phase increases and decreases respectively. If there is a mis match on either phase or one phase fails or they both fail,,,, the ECU goes into reduced power mode. You will be lucky to get the engine to rev over 1000 rpm in that mode. If the throttle blade sticks open, the engine will shut down.

Bill

 

Maybe not the problem, but extra and/or unanchored mats are just not a good idea.

 

Exactly! Known as "Fly by wire".

 

The above was written almost exactly as if I had written it.
Mine is a completely stock base 2005 6-speed, non-Z51 with 80k miles.

Last week, I was on the freeway passing some cars at full throttle in 5th, and when I pushed the clutch in to shift to 6th the engine went to redline while I frantically stabbed at the throttle pedal thinking it was stuck, but it was at normal height. After what seemed an eternity (probably a few seconds), it finally came back down to idle. Since last week, it hadn't done it again despite many full throttle attempts to duplicate it, making me think I had simply missed my shift and over-revved it that 1st time.

Until this morning. It happened no less than 3 different times this morning on the way to work.

First time a few blocks from my house, coming to a red light I let off the throttle but it was still pulling. It was still in gear so I held it with the brakes while I hit the off switch and then coasted to a stop. I kicked the throttle pedal a few times and restarted only to have the RPMs start to climb and immediately shut it down again. Repeated this at least 3 more times before it started and idled normally.

Then it happened again a few miles later coming to another stop light.

This can be pretty scary.

I guess the next step for me is to climb under the dash and check the throttle arm and cover for any obstructions. Then get it on my Snap-On scanner and see if there are any obvious codes, etc.

Any other suggestions or experiences like this?

Thanks,
Steve

 

Update:

I found nothing that could interfere with the accelerator pedal or it's position sensor.

If I understood Bill's previous posts correctly, the most likely cause is an errant signal from the Accelerator Pedal Position Sensor to the ECU, so I ordered a new AC Delco 2583542 Accelerator Pedal assembly from Amazon:





2005 C6 Corvette Accelerator Pedal Assembly





2005 C6 Corvette Accelerator Pedal Position Sensor

Hopefully that will solve this little mystery.

Steve

 

Another piece of info leading me to believe the Accelerator Pedal Position Sensor is going bad:

The new pedal isn't here yet, but I started thinking about how sometimes it would seem to me that when the car was cold, I seemed to be able to detect some surging at slow, steady state throttle positions in the lower gears. Reminded me of a carbureted car that would surge while the choke was on.

I have a Bluetooth OBD2 dongle with Torque loaded on my phone, so this morning I loaded the Pedal Position and Throttle Body position displays side by side and watched them as I began my morning commute.

Sure enough, while holding my foot steady, the pedal position display was hunting up and down within a 4% or 5% range with the throttle body trying it's best to respond to the constant changes.

To rule out foot movement, as soon as I got on the freeway I set the cruise control and the hunting continued. As the car warmed up, the hunting lessened until it finally stayed at steady readouts.

So it appears to me there is something wrong within the electronics of the Accelerator Position Sensor.

By the way, I'm sure it was easier to feel the surging in the lower gears, but the higher gears would mask it. My freeway test showed the hunting was still going on at freeway speeds, but I couldn't actually feel it.

One other thing, the Accelerator Position Sensor would not register more than 79% open. The percentage stopped climbing way before the pedal was on the floor, probably about 3/4 of the way down. Thus, the Throttle Body never went above about 88% open. (I was able to test this in my driveway with the engine off, ignition power on).

Steve

 

This is a very good analysis, well done. I suspect as you do, that your accelerator pedal is bad. Testing the APS next to the throttle position was the right test to perform.

What pid did you scan for the throttle blade position?

 

I totally agree with this analysis and have seen what even tapping a wire in the throttle body system can do to the car, it defaults to reduced power mode very easily, for obvious reasons, they don't want a Toyota class action suit. Mr. Curlee I think you're dead on with this.

OP, have you checked your system as Porxter did? Can you? If not I'd order an accelerator pedal just to be safe as it sounds like that's what's wrong.

 

The OP was 2 1/2 years ago and hasn't posted anything since then. I hope his car didn't take him out.

The Torque application doesn't tell you the PID, it just listed the 2 parameters available for my car as "Relative Throttle Position" and "Throttle Position (Manifold)" so I am assuming the first one is the Accelerator pedal.

Steve

 

Got it. I didn't look at the date of he original post.

I need to scan accelerator vs throttle on my buddy's c7z at the track but I'll figure it out.

Please let us know if this fixes your troubles!

 

Will do. Hoping it's not something in the wiring harness between the Accelerator and ECU like a random short in a reference wire or something like that.

I'm really looking forward to seeing whether or not a new Accelerator Assembly will give me 100% Throttle body opening!

I may have just found some "free" horsepower!

(Well, technically $72.33 for the new part, cheap price to pay for increasing from 88% to 100% throttle opening!!)

Steve

 

88% is actually 100% throttle. I forget exactly why but it's a fact.