2008 Gt500 Idle Failsafe mode

[Z71]

Hey guys im having some difficulties tuning my idle on my Gt500. Runs great, however every once in a while the throttle body will rev on its own and incrementally increase the rev until the engine goes into fail safe mode. What do I need to look at in my scanner and tune to correct this?

I entered the numbers from a supercobra jet file on here.

Thanks guys

GT500 6.21.17 MAF curve.hpt

[15PSI]

Can you provide a log from the scanner please? Warm the car to operating temperature, start log, idle for a minute or so, then do a driving log for 5 minutes. That will tell the tale.

[Z71]

Yeah I will do that here today. Anything specific I should be logging ?

[Z71]

Ok so wasnt sure what to log. I uploaded a different tune. So far this one doesnt kick it into failsafe mode like the other one does. It happens when I coast off the highway or come to a stop, the throttle actually gets away from me in some instances and then enters fail safe mode.
In the scan youll notice the idle oscilations coming to a stop. Both spark and rpm.

Attachment 71767

Attachment 71768

[Z71]

Ok so I did a few changes to the tune today it it made it incrementally worse. Engine revs on its own at idle then goes failsafe. Here is the tune and the log: [ATTACH]Bad tune log[/ATTACH][ATTACH]Bad Tune[/ATTACH]

So I went back to this tune which drives great, has very little issues but sometimes will rev on its own and go failsafe. Hard to replicate so I couldnt get the log for it.
[ATTACH]4.14 tune[/ATTACH]

[Z71]

I set my tune dashpot settings back to stock. Still have the issue. Went into failsafe mode at idle clutch in. Revs on its own and goes failsafe. Gave codes p2104 (throttle acutator control system forced idle) and p2111 (throttle a actuator stock open) .

8.23 idle failsafe.hpl

The times it revs in the scan are 14:44:18 and 14:55:36 which is when it went into fail safe mode.

[Devildog1325]

I would set all your idle airflow and dashpot back to stock. Most of the time all you have to do is log stit and ltit and apply the correction to your airflow tables. As long as your throttle body data is correct then you can start fine tuning with the torque and torque inverse tables. Then you should have a Monoblade that drives like the factory throttle body.

[Devildog1325]

If this does not help and you are still throwing codes after tuning your idle airflow tables you may have a defective throttle body. I believe it was Jn2 that had an issue with one a few weeks back and it turned out to be a bad throttle body.

[Jn2]

If you are using the super cobra jet throttle body(monoblade), then there is a high probability the TB is bad. I ran into the same issue on a customer's Shelby and Acufab kept telling him it was the tune and referring him back to me. So I took his mono blade and put it on my personal car(which already had a mono blade and ran perfect) and then my car ran like shit, sticking idles, wrench light, forced idle codes, forced engine shut down codes etc etc.

I ended up taking the motor off to check the TB's mechanical parts and noticed the bearing on the main shaft was coming out of it's hole. This would cause the TB to run into resistance as it tried to open/close, in some cases bind completely. I pushed the bearing back in and the TB has been fine ever since.

I too was plagued by this issue, trying different tune values over and over with no success bc of how intermittent the issue was.

[Z71]

Wow. Ok Ill check into that. Yeah I am kind of chasing my tail right now. Definitely dont want to get rid of the throttle body, but ill open it up and see what I can find.

[Z71]

Well I checked mine. Bearing looks good. Guess Ill keep trying to tune (I am new to the idle tuning portion so please bare with me). Now I am logging stit. I created a histogram for stit vs rpm. Now that i have those numbers do I just multiply vs the tune similar to tuning a maf curve?

Right now I am back to stock settings, however my idle is hanging up pretty high during shifts and idle. When this happens I assume I would need to drop the airflow tables to limit the airflow going to the engine?

Thanks guys

[Jn2]

Well I checked mine. Bearing looks good. Guess Ill keep trying to tune (I am new to the idle tuning portion so please bare with me). Now I am logging stit. I created a histogram for stit vs rpm. Now that i have those numbers do I just multiply vs the tune similar to tuning a maf curve?

Right now I am back to stock settings, however my idle is hanging up pretty high during shifts and idle. When this happens I assume I would need to drop the airflow tables to limit the airflow going to the engine?

Thanks guys

Try these settings, I used them on a 10' GT500 and mono blade TB and it idles like stock at 800-850rpm. A quirk this Shelby had(not sure if it's all spanish oaks) is that idle will hang after the reflash is done and you turn the car back on. Normally when I work with this one I turn car on, let it idle, rev it a bit, idle will hang, shut car off, turn it back on, let idle and then car will run perfect from that pint forward. If I flash a tune update then I repeated the process. It seems to only be a issue that occurs on the first start up after a flash...no clue why or if it's all cars or just his...

[Z71]

Yeah i forgot about the computer relearning the throttle body after each flash. Guess that was my problem earlier today. Ill give those numbers a try tomorrow and see what happens. Fingers crossed.

[Devildog1325]

Well I checked mine. Bearing looks good. Guess Ill keep trying to tune (I am new to the idle tuning portion so please bare with me). Now I am logging stit. I created a histogram for stit vs rpm. Now that i have those numbers do I just multiply vs the tune similar to tuning a maf curve?

Right now I am back to stock settings, however my idle is hanging up pretty high during shifts and idle. When this happens I assume I would need to drop the airflow tables to limit the airflow going to the engine?

Thanks guys

You need to add the values not multiply

[Z71]

**Update. Runs great now. Found a problem in my y axis settings. I was using data from a 2010 GT500 and guess it didnt like that very much. Used the stit values and added them into the tune and runs perfect. Thanks for the help guys.

[Devildog1325]

I'm glad you got it figured out!