Powerful then not

[Drewpgh]

Hello all, im new to the site. My name is Drew and I recently bought a 2006 gt with 16k miles and ordered a bunch of crap for it. As I'm waiting for my goodies to come in, I've been driving the car. It doesn't run as expected as far as power. it seems to run fine for the first couple of minutes then seems to lose its oompf. Not much power after 1/2 throttle or above 3000-3500 rpm. I'm getting the P0689 code. I have to come to suspect that a previous owner did an automatic to manual swap because the sticker on the door jam is coded for an auto. The car starts without the clutch being depressed and my cruise control doesn't work. Hoping you folks have some insight as I'm at wits end with this thing with and have a bunch of useless parts coming. P.s. I feel when the car is off my gauges move very slowly. I.e. When I shut the car down, my rpm gauge takes a while to return to 0. Thanks! Drew

 

[JeremyH]

Here is a start.

http://www.s197forum.com/forum/showthread.php?t=45209&highlight=p0689

 

[Drewpgh]

Here is a start.

http://www.s197forum.com/forum/showthread.php?t=45209&highlight=p0689

Jeremy, thanks for your reply. I did read that. I'm gonna start messing with the grounds tomorrow morning. Would this cause a performance problem? I can't wrap my head around why it would run well for the first minute or so then turn into a gutless wonder.

 

[JeremyH]

The other consensus besides grounds seems to be intermittent connection in the bec bus underhood that holds all the fuses and relays. If anything injector or spark related is intermittent you can get power loss.

 

[zquez]

The other consensus besides grounds seems to be intermittent connection in the bec bus underhood that holds all the fuses and relays. If anything injector or spark related is intermittent you can get power loss.

I have had this issue above before. The bolts in the engine bay fuse box weren't tight enough and vibration would cause the car to intermittently lose power and not run. In fact recently I had a similar issue that I traced to the positive batter cable not being secure enough on the battery post causing the same thing.

With regards to a manual swapped car, there are numerous issues that can arise from this being done, most all of them have to do with the ECU being confused as hell that there isn't an automatic transmission in the car anymore. If the auto engine harness was reused, there will be several sensors unused in the trans tunnel; not a super big deal. If the auto ECU was reused there are several safeguards in the software that cause it to run wonky. When I first did my swap, the car would start and run fine. It would even drive well for a while, until it realized it wasn't getting any sensor data from the shaft speed sensors and stuff at which point it would go into limp mode. A tune fixed that but eventually I also had an issue where there was a torque limiter because the ECU thought I was always in reverse. Yet again, a tune fixed it, albeit from a different tuner. I believe when the car first starts, it runs in a closed loop fashion based on a pre-programmed set of parameters. Once it heats up enough, it goes into open loop where it takes into account sensor data. It's at this point it realizes the lack of a transmission and starts trying to save itself.

It's highly possible this is a mechanical issue, but I would lean to it being an ECU problem that can be fixed by a tune. Lito is the resident expert and he has been the one to tune my car. No transmission related issues since I enlisted his expertise. Your other option, once you verify it is indeed a auto ECU, would be to get a manual one and swap them.

 

[01yellerCobra]

I had a similar issue in my Expedition. One minute it was fine, the next I had no power. I could floor it and the truck wouldn't go anywhere. Turns out it was a bad MAF sensor. If you have access to a known good one it may be worth a shot.