Master Honda Civic Tech (GURU) NEEDED! HELP HELP please

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I'll just dive right into it here...99 honda civic 4 door 1.6L non vtec auto. awesome running car, prolly my 8th civ ive owned. i installed the engine myself and drove it for a year and a half for a commuter 100 miles a day. i did the timing belt and water pump and everything was still great. about a month later i hit a little bump and the car sputtered and died out. cant remember the code exactly since it was about 6 months ago and i bought a new car. but it was the code for the IACV fault. i put a used iacv in and it ran just as it should...for 2 days! same thing happened again. i put a brand new iacv on it drove it for 2-3 days got it inspected no check engine light or any issues. while this was happening if after the first time it died you could unplug the iacv and it would run but just like the iacv was unplugged. then after that one time nothing. crank crank crank , no start. i traced all the wires and looms and saw no issues of wear or any problematic areas. so i replaced the ECM. started right up. about 2-3 times. took it for the first test run and it died about 5 miles in after going over a bridge (gap). thats where i am baffled. if i put a new part on it, it will run for a very limited amount of time then quit. all i can go with is its the harness but i dont understand how, if i throw a new iacv on it runs. very aggravating as i am staring at a perfectly good car that i cannot drive. please anyone if you have any ideas throw them at me. ive never seen anything like it before.
My first thought is wiring issue...even though you checked once....I would check again. Hitting a bump and the problem happening makes me think there is a short.

When it is running horrible (or not at all) check wiring (per helms manual troubleshooting guide) with a multimeter. Maybe it's a pin not fully inserted into the plug on the engine harness?
When you say you installed the engine yourself, was it a swap? Did you have to modify the harness or extend any of the plug wires? If so, I would check any spots where you had to cut and splice wires to make sure there's not a short in a spot you spliced and taped back together. What does the the distributor cap and rotor look like inside? If you've got a multimeter with long enough wires I would unplug the ECU and then unplug the sensor wires and check continuity from the plug wires to the ECU plugs. Don't just check the ECU pin that should go to the sensor plug, check each plug wire with every ECU pin to check for melted or shorted wires that are wrapped up in the wire looms.
Thanks for the replies. I actually installed a z6 block on the stock y7 head. Not the first time i did it. I'll have to get another iacv and see if itll run again and trace it till it quits. Hopefully that works
Yup, sure sounds like something is getting fried.

any chance a fuse was removed and jumped straight in instead?
Nah. The only thing i had changed but was fine for the year and a half i drove it was i believe the crank sensor (behind the lower timing cover)i had to re locate due to the z6 block didnt use one. But idk how that would make it throw an iacv code and then install two new ones and it run for a short time then die again.