Help with infiniti J30 "won't shut off"

[rwhite]

1996 Infiniti J30. New to me. Everything seemed okay but there was a 7.5a fuse labeled eng cont under the hood that was blown. I replaced the fuse and then the car would not shut off. Pulled the fuse then everything work work correctly. Issue is that there is power to both sides of the fuse when it doesn't seem like there should be. Any ideas? What does this fuse control?

[chiken7]

interesting...cause i recently checked the hood fusebox and replaced a missing injector fuse.
what is 'eng cont'?
anyway, i think the cheapest way to solve the issue is to reset the ecu and see what happens.

[rwhite]

Not real sure what eng cont is. I assume it's engine control. I have reset the ECU with a code reader but I didn't want to go monkeying around to much until I figured out why that fuse has power to both sides. HAte to fry an ECU. THe schematic shows it as fuse #58 which controls main, mafs, cmps, ign/sg.

Again I assume that MAFS is the flow sensor, CMPS is the cam sensor or crank sensor. I have no idea wha the ign/sg or main is.

[rwhite]

I have searched until my eyes are blurry and found no solution. Did find a few posts but no followup on solutions.

[rwhite]

As far as I can tell (even wih the issue) evrything is running correctly. I pulled the ECU cover off and there is no apparent burn marks or anything to make me beleive it's bad. Time to check for ignition short

[chiken7]

yeah...sounds like you're on the right track.
Q: did you disconnect the battery before/after ecu resetting w/reader?

[rwhite]

I have traced every possible thing that I can come up with:

1. Took ECU apart. No apparent burns
2. Unhooked every sensor, relay, fuse etc. The only fuse that would change the issue is if I pull the 20 amp
ignition fuse. If I pull that I'm back to only having power to the correct side of the engine control fuse. But of
course the motor won't run without it.
3. All relays test good and I swapped the ones around that were similar. Nothing changes
4. All coils are firing and all injectors are working. Pulled each one while running to confirm.
5. MAF is working as far as I can tell. Idle changes when I pull the plug anyway.
6. Traced every open wire. None are burned or apparently shorted. I tested continuity where I could.
7. The only code I would get is for EGR. So I'm not sure if that is bad or the fuse issue is causing it. Even unplugged I still have the problem

So at this point I'm stumped. I'm leaning toward a bad ECU or ignition switch. Even though nothing is apparently wrong I supposed it still could be. Just can't understand how everything seems to be working correctly and the car run fine.

BTW: I reset the codes with the reader and from the ECU. The car won't throw a code at idle and ususally it's a few days and I'll get an egr code. No other codes present.

[rwhite]

Think that I found the issue. When I got the car the MAF was not working and had a cobble job on the wires. I put a new maf and pigtail and everything seemed good. I did not check the engine control fuse at that time to see if it was blown. After 2 days of searching it seems that if a MAF shorts out it will cause my exact symptoms. Apparently it fries a diode in the ignition circuit of the ECU. With the wiring job that was on there I'm assuming that at some point the MAF had shorted. Going to order an ECU and see if that solves it.

[rwhite]

DOn't know if I will ever find the answer to why the 7.5a fuse has power to both sides with the ingnition on. There is a 1.5v difference between the sides. But I got a new (salvage yard) ECU and it stopped blowing the fuse and the car will turn off now and no check engine lights so I am guessing that it's fixed unless I find out something different.

[chiken7]

yeah...again, it sounds like you're on the right track.
didn't know problem with maf can cause all that havoc.

Q: did you open the ecu to look for burnt/melt/smoke marks?
Q: did you try cleaning your maf sensor after rewiring?

[rwhite]

yeah...again, it sounds like you're on the right track.
didn't know problem with maf can cause all that havoc.

Q: did you open the ecu to look for burnt/melt/smoke marks?
Q: did you try cleaning your maf sensor after rewiring?

Everything inside the ECU looked good. No burn marks or anything but I still think it was bad because it was blowing the fuse. New ECU doesn't blow the fuse

MAF has been cleaned and it working properly.

The question still remains as to the fuse. Maybe someday someone will pull their 7.5a engine control fuse, turn the ignition on and see if it has power to both sides. Then I'll know. Until then I think it's just you and me on this forum.