Fierofly

iTrader: (1)

Been driving the heck out of it on nice days, have been getting a check engine light about every other day, P0507, I just reset it for now. Still haven't had it tuned yet. Runs great except for a low speed surge under 30mph, hoping it just needs tuned.

Now the big problem yesterday, the throttle just quit after some serious playing, 1000rpm and no throttle response (Ck Light ON), so I pulled over, turned it off and restarted fine but still no throttle. Disconnected the battery and now everything works fine. Problem is, I have no stored codes cause of battery disconnect, so Now what? I guess I'll take the computer with me at all times and wait for it to happen again, that could get dangerous though.

Any suggestions?

Amille28

I'm having the same problem. I am away and can't get to the bottom of it. I think we will need to record our APP sensor values. If the ECU gets more voltage than expected from the pedal it thinks there is something wrong with the e-gas pedal and will go into limp mode.

Fix could be to just put a stopper behind the pedal to prevent it from going over 100%

http://chevythunder.com/drive_by_wire.htm

Fierofly

iTrader: (1)

Are you using the Porsche pedal also?
I'm also having a slow speed surge 20-25mph, wonder if this could be the cause.
Also when I do get a P0507 code and I check the freeze frame the throttle positions don't read the same. like position A or 1 (can't remember what they're called) will be 18% and B or 2 will be 27%. I guess I'm just going to have to spend the money and take it to a tuner or at least not go 100% throttle till then.

Amille28

I too am using the Porsche pedal. My issues are worse but I think related to me using a truck throttle body. When I get back home I will get a corvette throttle body as right now going WOT with the pedal only gives me 70% open throttle and so I can only accelerate to 4000rpm.

The pedal signal voltages are what we have to look at and compare to the corvette pedal. From what I read the low voltage (pedal not depressed) has to be above 0. If it were zero it would set a code saying there is no pedal signal. So if your low voltage signal on your pedal is higher than the idle corvette pedal signal, i could see you getting that code.

Some scan tools will read APP signal voltage 1 and 2. I need to read these and see how they compare to the vette pedal and if the voltages in the ECU can be tuned.

Fierofly

iTrader: (1)

Also I noticed in the Porsche manual it talks about a resync that is required when you change the throttle body, something about turning on the key and holding down the pedal for so many seconds or something like that, that makes me think that I have to sync the corvette body to the Porsche pedal somehow. Hopefully a tuner will know how.

smitty2919

I don't care for car shows anymore because there are less and less people like the OP...it's either old 100% restored cars, which I find more appealing than a brand new car but still slightly bored with, or people that buy brand new ****.

The old restored stuff tells me you dumped a lot of money into a car and NEVER drive it...a waste IMO. The NEW stuff tells me you were lazy to restore something so you buy a car for $$$ and don't drive it to show you have money...again a waste LOL.

If I was at that show I would have been looking for the OP to talk to him to see if he did it himself. In which case I would have been very happy to know he did and didn't pay a shop to do it.

Well done sir!

Fierofly

iTrader: (1)

Thanks for all the compliments!

More on the throttle pedal saga, I took off the air cleaner pipe and moved the pedal while watching the TB (throttle Body), I know, I should have done this a long time ago during the build. I always noticed that I had to move the pedal about 1/2" before I got response. The Porsche pedal works through a cable to an actuator under the dash (not fun to get to). I just figured I needed to adjust the cable a little. So I got under the dash and observed that the cable moves the actuator right away and when I move it full, I only get about 7/8 full open at the TB and there is no more movement left on the actuator. So now I'm stumped and really don't want to go thru the hassle of installing the GM pedal. Any thoughts ?

DW SD

I assume there is a CAM that rotates a TPS potentiometer as the cable pulls?

can you change the leverage of one of the parts to gain more throw?

Fierofly

iTrader: (1)

Yep, but as soon as I touch the pedal the cam moves, I'm guessing that the initial signal sent is not enough to start the TB to move. unless there is NO signal till the potentiometer moves to a certain point. I think I'm going to have to research and figure out what wires to check at the throttle body and WHAT to look for volts or continuity or ???

DW SD

just measure resistance as you sweep the pedal on the GM and then compare.

Doug

Amille28

A scan tool should be able to pick up APP sensor 1 and sensor 2 voltages if it has the capability to stream data while the engine is running.

If the voltage is 0 with no pressure on the pedal a code (not sure which one) will set thinking there is something wrong with the pedal. I dont think you have this problem. I'm not sure if theres a screw or something on the pedal that we can take up the slack.

As the pedal gets pressed APP sensor voltage increases and APP sensor voltage increases at a slower rate (like 50% of sensor 1)

If when the pedal is fully depressed the voltage is greater than what the ecu is programmed to see (greater than 100%) the car will go into limp mode.

I'm not sure if a tuner can change the voltages the ecu expects to see or not. It should be possible but I dont' know anything about it.
There is a company that sells a unit that modifies these voltages.. all it does is increase the rate of voltage change to increase "throttle response"
this doesn't fix our problem.. because we want to ensure that no pedal and WOT voltages match what the GM ecu wants to see.

Jhunter

Sub'd. I'm gathering data while saving money for my build. The more tips on the front end should help me later. Thanks to all who have posted!

Amille28

Have you thought yet about AC. I have to make a long drive with the car pretty soon and am thinking about going with an 04 corvette compressor. The LS3 compressors are more expensive. Both should work with the corvette crank pulley setup I have installed.
What do you think?

Fierofly

iTrader: (1)

I've got the LS3 compressor mounted and wired. Need to plumb the hoses and charge system soon, I'm still driving with 80% throttle, haven't had it tuned yet. got about 1800mi. driving between rain storms.

Amille28

Can you give me a quick tutorial on the wiring. There are two wires on the gm compressor. one is hot and one is ground right? The signal wire on the porsche side should be hot. So did you just find someplace else to ground the other wire?

Fierofly

iTrader: (1)

I was just going to run it to ground and see how it works. As far as increasing idle speed and that kind of stuff, I don't think idle will change with compressor engaged cause GM computer will adjust when it senses a load on engine, maybe ????

Fierofly

iTrader: (1)

Replaced the shoes, we'll see how it affects it as soon as the weather cooperates.

Removed 295/30 R18 and 225/40 R18
Installed 295/30 R19 and 225/40 R19

Raised the ride height by 1/2 inch

Amille28

Mike,

Selling the old rims?
I like the new turbo style rims.. your car looks way better than mine.

OS inspector

Nice build, Subscribed i have a 2001 996tt almost went this route when the engine came apart.

Fierofly

iTrader: (1)

It has been awhile since I've posted anything, so I figured I'd give a quick update and some pictures of what's going on.
Been driving it up till now with a few minor problems and I decided to take the time and fix a few.

1. The Porsche throttle pedal has only been opening the throttle body about 70-80% and I keep getting a throttle idle code, so after a few discussions with some people that know I decided to replace the Porsche pedal with a GM. Also if I held the Porsche pedal to the floor I'd lose all throttle movement till I disconnected the battery and reset GM computer. The GM pedal I got with the GM off road LS3 computer has an awful mounting bracket so I purchased another new GM pedal that was recommended, see pictures below. I wired it in and checked throttle body and now have full 100% movement, this should be a lot more FUN.




Also note the difference in the electrical box size, don't know why, but doesn't seem to make any difference.