OK so i went to the mall recently the car drove fine on the way there, when i went to leave the car started fine but idled extremely low, not sure exactly how low (my tach is not working atm) but it was struggling to keep itself alive, also the AFRs were running very rich (between 10.5-11.5). I dont necessarily think its a vacuum issue, my gauge was reading 18-20ish inMg. Along with all that i threw a bunch of codes im at work rightnow so i dont have the exact list with me but the ones i remember were,
23
26
32
33
40
42
43
44
45
54

i think thats the whole list, ill double check and repost when i get home tonight

ive been sitting on this computer for like an hour trying to figure it out and im at all loss


but anyway me and my buddy are thinking that it could possibly be a grounding issue, i do have the battery relocated to the trunk with it grounded just on the metal under the carpet, when i get home ill try re-grouding it on the strut tower or something. but anywho


HELP ME lol its gonna be really hard to get to work and class without my car


oh and btw the car is bone stock with a '94 JDM engine in it and a racing beat exhaust,hi-flow cat and down pipe.

 

just in case anyone else has an issue like this, the problem turned out to be a shitty main battery ground

 

Glad you fixed the problem, and nice that you followed up with the solution.

I had a bad block ground that drove me nuts for a while too. gotta love electrical problems.

Did you relocate the ground or figure out why the spot you chose wasn't working?

 

when i bought the car it already had the battery relocated to the trunk and it had been grounded on a sanded down patch of truck metal. Well upon inspection it had rusted in the humidity a little and messed up the good connection. I just regrounded it on the strut tower and it worked fine.

 

OK so im completely stumped and i have no idea what to do anymore.
First lemme describe the problem:
Car will run for a while then out of nowhere ill turn it on and BAM limp mode and almost every single code being throw. My mechanic buddies and I used to be reasonably certain it was a grounding problem, i mean why the hell else would ALL my damn sensors stop working at the same time, but now were not so sure.

Codes being thrown:
23
25
26
30
32
33
34
40
42
43
44
45
46
50

This has happened before however, and when it happened the first time my first assumption was that it was a grounding issue (when i bought the car it had the battery relocated to the trunk) so I did some electrical work and regrounded the battery to a more solid location, reset the ecu and it fixed it, or so i thought.

well it happened again this morning on my way to class of all places *sigh*. well i assume its a grounding problem agian like it was last time so i start checking grounds, I check my battery ground again only to find out the wire had come loose from the terminal. Fixed that still throwing codes out the ***. I check all my fuses and a couple look iffy, not blown, just sketch. So i replace all the fuses, still no dice. I then just started checking all the grounds that i know of. The ones i checked were the one on the chassis on the engine bay under where the battery goes stock, the ones comming off the top of the block, the harness ground that attaches to the bottom of the block. They looked fine, contact was good, no corrosion etc. Yet after doing all that nonsense im still f****** stumped. This has exhaused the range of my expertise and im at a loss. If anyone has ANY insight into what could be causing this crap please save me.

 

what ECU are you running

 

stock ecu, the engine in it is a '94 spec JDM engine.

other mods:
gauges
boost controller
exhaust
intake
fmic

 

id assume its something with the ECU, try finding another stock or moving to a power FC, if the issue is still there id assume its a major ground issue, check all grounds that are on the motor.

 

that would be a PITA if it were a bad ecu, that would make the SECOND bad ecu ive had in this car lol, when it rains it pours i guess

is there a comprehensive list of the grounds on the car somewhere that im just being dumb and cant find?

 

Just spring for a new(er) emissions harness and most likely all your problems will go away.

 

I've experienced a problem similar to yours that turned out to be a corroded pin & crimp connection in one of the ECU's connectors. Specifically, my problem was related to pin 1B, which supplies switched 12v to the ECU. Similar problems could be introduced if any one of the several grounds at the ECU have problems. Look carefully at the heavier wires/pins/crimps on connectors 1 and 4, in particular. Repair/remake any connections that show evidence of corrosion.

*It is important to note that if the ECU sees a reduced voltage at pin 1B relative to its ground for any reason, it will automatically richen up due to its internal injector lag compensation. (You guys that have tapped into switched power from the 'fuel injection' or main relay should note this as the voltage drop caused by an excessive load may cause the ECU to richen the mixture, dependent upon the current draw and where you've tapped in. These are the heavier wires: black w/white stripe, black w/orange stripe & the black w/yellow that are found in the front harness and engine management harness.)*

ECU failures are rare. For purposes of diagnosis and repair, I don't recommending swapping out the ECU unless it's with another identical factory ECU; otherwise you're just introducing more variables and opening another can of worms--so to speak.

 

hmm good info speed, that's another thing that ill look into when im in a position to tear apart the car.

 

OK update: i am at a complete loss...nothing ive done has fixed anything at all

what ive tried: checked and sanded down/fixed/rewired every ground on the EM harness and the charging system harness, added a few of my own extra grounds on the tranny and block. unplugged the battery and let it sit overnight to realllly reset the ecu. and followed speeds suggestion of checking the pins going into the ecu. After all that i turn it on and it was running ok (ok meaning it wasnt in limp mode and i wasnt throwing any codes but i had this very strange boost hesitation issue) so i drove it around the block and back to my place to see if i had a vac leak or something, went to start it up again and BAM back in limp mode back to throwing all those damn codes.

Im starting to think that there are just a bunch of cracked wires in the harness and im getting some nasty shorts. I cant really afford to buy a new harness so i was thinking about pulling the old harness out and rewiring it by hand.

anyone else have any suggestions?

 

rewiring that harness by hand will be a metric b*t*h, but if your on a budged, but some 20ga insulated wire in every possible color of the rainbow and get crackin. While your at it, you may want to consider simplifying things in the engine bay and running the car with a simplified seq setup, 330ohm resistors to get around the solenoids. Another option is to borrow a PFC from someone else in the area, I'm sure there is someone around who can hook you up, or point you in the right direction.

That being said I don't think its a wiring problem like what your thinking, before you go ripping stuff apart just run a multimeter around the ECU plugs and check continuity to the sensors effected. Try a new battery if you can just as a precaution, and check and see if all the effected sensors and solenoids are on the same plug of the ECU harness since this can narrow things down a little.

In any event good luck with it, it looks like you'll need it

 

Id already checked a multimeter at the pins, as well as double checking that the sensors and solonoids were hooked up to the right plugs.

on a side note im fairly positive that its a wiring problem now, i pulled the harness earlier and as i was pulling the loom off the wire insulation started cracking all over the damn place, as well as one of em straight broke in half lol.

im not too worried about rewiring it by hand, im an electrical engineer so wiring is what i do haha. I also helped my buddy rewire his civic a while back so im familiar with the process anyway