Hondata

hi all.
i have a 92 civic b16a2, fully built, with crower stroker kit and a garrett gt3076 turbo. car ran great for a long time now, but on saturday morning, i turned the key, and the fuel pump didn´t go on. at the 2nd try it worked. let the car warm up at idle for about 2 mins, and started to drive. but after 200 meters, the engine stalled. when i switched on the ignition, i heard the main/fuelpump relay and the fuelpump switch on-off very fast, and the mil stayed on. but i do not have an errorcode on my s300. also the led at the usb is red. but after a few times turning the key on-off, the runs great again.
this happens when the car is warm, cold, standing still, when driving, or just over night.
i have changed the main relay -> no change
checked the ignition lock -> no change
the grounding at the thermostathousing is perfect, but when i disconnect it, everything is still working!? isn´t this the main ground of the ecu and the main relay??
and yesterday, when i checked everything, i plugged of the usb from my carpc to the ecu, and it worked. but later i did the same and it didn´t help.
does anybody have an idea what can cause this?
the datalog shows it when it happens, but it´s loosing connection, when this happens.
thanks for trying to help!

i forgot to tell, that i was driving for 4 hours without problems yesterday, and after a stop at the gasstation, it happened again!!

What has recently changed or been worked on in the car?

nothing. i was driving till thursday, w/o issues, on friday morning it started doing this. car is in a garage, no animals or idiots!

Since this is intermitent, the 2 most likely causes are either faulty wiring, or possibly the main capacitor in your ECU is going out.

Try the ECU in a known good car and see if the problem goes away, if it does then you know it is wiring.

no other hondas here to try. is there a way to measure the ecu?

here is another log. it´s funny, that s300 is loosing signals, but still recording!? but why the mil and no error?

Graph your battery voltage. It should be steady at 14V, but instead falls to 12V every half minute or so, and also is not very smooth.

Find and fix what is causing the voltage at the ECU to drop. It could be the alternator, the main relay, the ECU itself or any of the parts in between.

BTW don't run the ECU with the thermostat ground disconnected. The ECU will still run by grounding through some of the sensors, but once you put a lot of current through them, usually at VTEC, bad things happen.

I tried the grounding without starting the engine to damage nothing. And the voltage drop is because of the fan. When he switches on, the voltage goes down and up again. Already tried it without, when the engine was cold, and had the same issue! I just opened the ecu but all the capacitors look fine. Which one can cause this problems?

okay. after hours of checking the wiring, resoldering all connectors, changing all caps and the main relay, i have the complete wiring diagram in my head. but long story short, the problem was something different.
i just found out, that there is also a problem, when i touch and tap on the ecu. the reason for was a bad socketing of the s300!! after 5 years, the connectors must have got bad. just pulled it out and pushed it back on, tataa - it´s working again!
thanks for the replies, but we all learned something more now i guess.
maybe this post helps somebody else in future!!
greetz