Got the switch installed:
Timing setting for Premium gas is +3 degrees (advanced), upper position, Regular gas, -3 degress (retarded) at the lower postion. The center position is unchanged stock ignition setting.
............. I'll try and get some more information and post back later.
OK need to post new results with the EZK mod.
I took a long trip to CT to haul a 2500 lb load of things from my family's home back to TX and during my first hour out of TX with the trailer nearly empty, ~1000 lbs total, I got really poor mileage 18 mpg, and low power with A/C on at 60-70 mph.
I had regular gas in the 245 when I left, so on my first fill-up I put in premimum gas and flipped the switch. Great! Fantastic! The car pulled wonderfully, even up hills at 75 in 5th. The advance plus premimum really performed well once the ICU/ECU 'learned' the settings. This made the 245 drive great, not since I've been using regular gas mostly since I did the mod. When I filled up the trailer with the load, the car hauled ass, even stronger once the ECU adjusted fuel to the bigger load, 21-22 mpg on premimum. I also added Lucas fuel conditioner and octane boost with Sunoco 94. Zoom, even those big hills on I 70 in Western PA and Wheeling WVA were no challenge to the brick, the car drove flawlessly.
Well that was great. Until I stopped at a gas station in Illinois that only had regular gas (Marathon, yeech!). I quickly flipped the switch back to 'Regular' for less advance. Car ran like crap, started running hot a few hundred miles later. Then the ignition started to stutter, and then the engine stopped running. I pulled over and checked the on-board diagnostics and found the crank sensor was faulty, and 2-3-1 code also. It did feel like the crank sensor was bad, but had recently replaced it, didn't make sense, bad aftermarket part?
Anyway, when I tried to start the car again, maybe an hour later, it started right up and ran OK for about 40-50 miles, but started all kinds of wierd ignition related problems, A/C high idle was going up and down every 3-4 sec, the throttle position sensor was making the engine jump then surge, as well as the engine cutting out like the crank sensor had an intemittent prob. I got the car to an exit and sat in a Denny's figuring what to do over a Moon Over My Hammy and a Coke, then started out until it acted up again.
So somewhere in southern MO I pulled over and let the engine cool down for couple hours. It was 99 deg and 85 % humidity and I was sitting on the side of the Interstate about 120 miles north of Memphis in Bum-F**K Egypt. )It really was just south of Cairo!)
I though, what about my ignition mod?
I looked at the ICU connector and though it may be out of the socket, so I re-seated it as well as removed the ign mod wires I added to the harness. I continued toward Memphis and all was well for about 50 miles, then the erratic behavior started again. I reached over and pulled the panel down that is under the glovebox where the ICU was, and then grabbed the ICU to feel if it was hot, and it was. A soon as I dangled the ICU into the passenger compartment and had removed the panel so it could get a cool air flow, the car began to run much better, and in about 5 min was fine. I happend to have a small cooler filled with ice, cokes & bud's on the floor so I put the ICU in the cooler where it stayed the rest of the way to TX. I filled the car with premimum gas, left the ICU in stock un-modified condition for the next 17 hrs until I arrived home at 5 am the next day.
The car has run great since, even with the ICU not on ice, have done nothing except let it hang, have driven it every day here commuting to work, 105 deg and a/c cranked. The mod is still disabled.
So the story here says that at some point I cooked the ICU. Was it because I flipped the switch after running regular? Did the ICU get over-worked by re-learning everything? It was running so good when I had the advance set for premimum.
I know this question has been raised before whether or not something like this could happen. Well it can. Still not sure if I need a new ICU or just don't mess with it. My nature says 'don't mess with it' and surely I angered the brickster gods by messing with my beloved VERY reliable 245. I have NEVER, that's NEVER had an ICU go bad, and that's maybe 25-30 200/700/900 I've had with an EZK.
I have NEVER had a serious road trip breakdown before, this was a first in probably 60 cross-USA trips and millions of miles. I'm going to leave it alone.