shutting off while making a left turns

[bobolow]

hello, new to the forums and some what new to repairing my ls which i've had for over 5 years now.

all started yesterday, hard left turns shut the the car. some shut downs are complete loss of power even hazard lights wont work. other times the car will turn right back on after about a second and i just drive off. will not do it to right turns, hard stops or accelerations.

what i've done:
tested the alternator loaded and unloaded, all worked fine, charging on it was ok too.
battery tested fine (optima)
tried to make turns with tcs on and off, both result in same thing, although when off the car is less likely to start or resume itself
checked to see if there was anything in the was of the tcs sensors, all was clear down there
does it at 1/2 and 1/4 tank full of gas
only fault codes are related to cats, codes have been there for like 1 1/2 years

now im stumped,maybe reprogram pcm? thanks in advance

 

[bobolow]

oh, its an 04 lincoln ls v6

 

[joegr]

1. The Optima is not a good battery for the LS. Even the Optima guy said that. If you must use it, then at least rig a connection between two vents and the vent tube. Hydrogen gas in the trunk and the interior is dangerous. Corrosive gas in the trunk is bad for the electrical system.

2. Check the battery cables (both ends of each cable). Check the relays and relay sockets in the trunk. Check the power junction behind the front passenger wheel.

 

[bobolow]

i checked the cables and fuse box in the trunk and they all seem to be fine. the power junction behind the tire, is that under the hood on in the cabin?

also i tried driving with my head unit off, and hasn't occurred this morning thus far, could that affect the engine? its a kenwood ddx7019

 

[joegr]

Under the hood. Actually, it won't matter if the hood is open or not. It's in the wheel well. Take the liner out.