tune is attached, fought with my last 03 ecu doing the same thing , where you would write the pcm it would start, run great then just shut off 30 secs or so later.but you would key off, then key on to go start it, no fuel pump cycle and it wont start. but if you write the pcm again, it will start and run, but repeat the same thing for about 3 times and then keep on running fine, so today-I wrote my 05 pcm to 3 bar speed density and set the tune up, and it does the SAME thing, key on starts, runs, 30 secs, dies , no fuel pump no start...then write pcm it will start and run, but repeat, this time it will not stay running like the last pcm?..Is this meaning both ecus are bad? is my tune bad? I don't get it! thanks in advanced for the help!
Im still new to tuning so I wont be too much help but I thought I would throw in some ideas.... From all the info I have gathered in my research, it seems the PCMs are pretty robust and to have one be faulty in a manner that you are stating seems extremely unlikely, let alone the exact same thing happening to TWO different PCMs. I notice your thread title states that you have a motor swap. My gut feeling says that it is an electrical issue you are having. These motors are extremely picky with grounds. When I first tried to fire mine up (LQ9 into 95 obs), it would crank and crank but no fire. I finally found one little tiny ground I forgot to hook up..... as soon as I wired it in, the motor fired right up. This is a common issue with LS swaps.
My question to you is, when it dies, does it stumble worse and worse until it dies out, or does it just straight up cut off? If it is stumbling, then its possible you dont have the fueling or air tables correct in that once it starts to warm up and move through the tables to drop the rpm, change the spark and air, its possible you are flooding it or something of that nature. Have you tried a stock tune? Not sure what mods you have. If the motor is pretty basic, try a stock tune and see what happens. Now on the other hand, if it just cuts out, out of nowhere, you might have an electrical issue in that when the motor is running, it vibrates a wire loose, or maybe a wire(s) are close to exhaust manifolds and when it heats up, expansion, and the connection goes away, then when it cools, the contact comes back and you can start it up again....
Like I said, im new to tuning, but that is where I would personally start for process of elimination. Hope that helps.
yeah it straight up just shuts off like if I were to shut the ignition off. the 03 pcm would stop having this symptom after the 3rd time re writing the tune in.... this 05 pcm I tried re loading the tune 4 times and it stayed running only for the same amount of time everytime… all grounds are good on the standalone harness, I double checked that. I thought it could be coolant temp related because it would straighten out after the 3rd time or so...not sure where to go from here.
I have not honestly. ive been meaning to set up a fuel pressure sender and guage on the truck just to have for good measure. but I don't think its fuel pressure related because it literally just stops running. and if you key on after it dies normally it would cycle the fuel pump for a few seconds. but the pump just clicks on and off fast. then when you write the pcm again it cycles the fuel pump when you key off then on and it fires right up, runs for 30 secs or so and just shuts off again...
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