Reduced Engine Power

[Kfred 513]

I'm having intermittent issues with reduced engine power. When it happens I get no accelerator pedal response. I took a log to help diagnose and found the following:
Accelerator pedal channel logs correctly 0-99% as I press pedal
Throttle blade responds correctly 0-90% when manually moved.

However, the throttle blade does not move when I press the pedal with ACC on, car off. Not sure if that is normal or not.

When I first start the car I can rev it, and it runs normal for about 5 seconds until it goes into reduced engine power, so everything seems to be functioning as it should until the ecu shuts it down.

At this point I don't know where to start because I don't have the typical codes that point to a faulty accelerator pedal.

Does anyone have any ideas?

[TCSS07]

post tune file...what vehicle?engine?mods?dtc's? you can have a failure with the throttle body, 5 volt ref circuits also or it may be as easy as turning off a few tests under engine diag

[Kfred 513]

The car and mods are in my signature. I think it's the throttle body, we connected a gold blade from an 09+ Z06 and the throttle opened with the accelerator pedal with the car not running...my TB didnt open at all. The log shows the throttle opening with pedal. The car wouldnt run with the gold blade TB, it only started and then shut off immediately. I cannot find any other real information online about the differences between the silver/gold blade throttle bodies other than they function different...nobody seems to know how.

I plan to call Dave at DSX on Monday since im running his 2010+ ECM..there must be a way to make the new TB work with the newer ECM.

track day read.hpt
gold blade test.hpl
dtc.PNG

[TCSS07]

yeah seems to be something going on with the tb
couple things i noticed in your tune - if your going to run ve only set your dynamic airflow high rpm disable to 8k and re enable to 7900 because your still telling the ecm to use maf above 4k
Disable the p0068 test by setting it to 8k because ive had that test still enabled be a issue with big tb's and causing R.E.P. and you may want to disable the tests for p0101,p0106 and p0121 set min ect to 493 as it will may also cause a R.E.P.
since your still on a 1 bar os and in ve mode your spark will default to the low octane chart so you must copy your high octane over to the low octane to get the proper spark

[Kfred 513]

yeah seems to be something going on with the tb
couple things i noticed in your tune - if your going to run ve only set your dynamic airflow high rpm disable to 8k and re enable to 7900 because your still telling the ecm to use maf above 4k
Disable the p0068 test by setting it to 8k because ive had that test still enabled be a issue with big tb's and causing R.E.P. and you may want to disable the tests for p0101,p0106 and p0121 set min ect to 493 as it will may also cause a R.E.P.
since your still on a 1 bar os and in ve mode your spark will default to the low octane chart so you must copy your high octane over to the low octane to get the proper spark

interesting, i had never heard that the low octane spark table will be default when in SD.

Thanks for all of those tips. i'm going to make all of those changes and see if it makes a difference. I have been driving the car this way for quite some time and only had this issue pop up one other time.

If someone could take a log, or visually check their throttle body operation it would be super helpful and greatly appreciated.

I need to know if the throttle blade should be moving when the pedal is pressed with the car off - key on. Mine doesnt, and doesnt show a change in TPS%.

[TCSS07]

It only reverts on a 1 bar os. if you upgrade to the 2 bar you don't have to worry about the spark using the low octane and with the 2 bar os you would get a actual ve table and not have to deal with the coefficients and as for the throttle it depends I guess on the ECU because at work when I do throttle services and the tb is in a bad spot and don't want to remove I'll key the car on and hit the pedal to open the throttle - on some cars it works and some it doesn't

[Kfred 513]

I'll look into the 2 bar OS. I like the idea of running a true VE table.

I'm just wondering why my stock TB didn't open, but the good blade did. Both tests were on my car, same ecm. Is it because the gold blade operates different, or because mine is operating incorrectly.

I am diagnosing DTC P0690. I am not sure if that code appeared because we connected the gold blade, or if it has been there. I am confused by step 6, and have included a picture. It seems to direct me to test 3 circuits, but it may be poor wording. Can someone clarify?

For some reason i cannot upload the picture of the troubleshooting steps. i typed it below.

"If voltage is present, test the ignition 1 voltage circuit between the ECM, the powertrain ignition 1 relay, and the ETC fuse for a short to voltage. If both circuits test normal, replace ECM."

[Kfred 513]

Just want to post my resolution for people with this problem in the future. TCSS was right, the P0068 code was causing my car to go into REP. For some reason the car decided to not like the MAF being disabled. I had been driving the car with the MAF disabled for over two months before it threw the code and gave me an issue. If your MAF is disabled, and you have a P0068 DTC, follow his instructions in post #4 and hopefully your problems go away as mine have.