Zealot Prime

So here's my car's deal: I was intermittently having trouble with the car dying when you first hit the throttle, and occasional missfires. It went away for a while, but when it started getting colder it got worse to the point where making it out of a parking lot would require restarting it like 5 times. Once it was up to speed, it ran fine. I took it home, and after it sat for a while it wouldn't restart at all. It seemed to not be getting fuel, so I replaced the pump and filter; still no.
Today it was warmer and the car started, but idled rough and low. Touching the throttle caused it to die immediately. After letting it run for a bit, I got the code 16 light.
Tested the continuity of the injectors, they all seem fine. The next step is that there's supposed to be 12v between the yellow/black wire on the injector clip and ground with the key on: I can't find voltage on any of them, which makes no sense to me.
I can hear the main relay click, the fuel pump come on, and the CEL goes back off after the pump primes so the relay should be good, plus how could it have started at all if there was no power? Halp!

usajags84

I am thinking a couple of things but. I am an amateur. I would check the power going to the ECM I know you checked the main relay but just incase there corrosion on any of the junctions
I could be the ECM failing but that makes me question how did it run before. Did you check the pressure on the rail and see what it is?

ezone

What kinda car? Year? Post this stuff at the beginning of any thread you make, I hate searching peoples history to find critical info.

the car has a F23A with a prelude SI trans? Years?
What was the ECM for and what year?


Yel/blk is only supposed to have power when the main relay is engaged, key on....Could be a main relay problem, there is more than one part to that relay. But if there was no power there, the engine couldn't run at all.

Code 16, fuel injector circuit.....
I'd try to figure out which cylinders its missing on first, that way I have a clue which injectors to be paying closer attention to.

I'd go to the main relay yel/blk and the ECM and ohm test injector circuits from its connectors, that way you are checking wiring and connectors instead of disturbing them on the fuel rail. I'm thinking loosely fitting female terminals in the connector shells. If you find one with a wrong (high) resistance then wiggle inj connectors while watching the meter.

Zealot Prime

Yeah, sorry for not including all the info. I didn't think it would be that relevant, and was afraid of posting a novel.

I haven't checked the fuel pressure with a gauge yet, (I bought a gauge, but then discovered there was no non-pain-in-the-*** way to attach it without at least finding and buying a special adapter) but if you loosen any of the fittings, gas sprays out. Plus: brand new pump and filter.

I'm not sure which ecm it has, I'll try to dig it out to find out. I was told by the guy I bought it from that it was chip-tuned, so I assume it was the original civic LX one, but I'm obviously no expert. For all I know, you can't even chip those.

I looked at some main relay diagrams, and I thought the circuit that supplied the injectors was the same one that supplied the ECU, thus the ECU wouldn't have power if they didn't, and that there was another relay for the fuel pump. I'm assuming I read them wrong, or the wrong one?

So: what you're suggesting I do is test between A1, A2, A3, A5 and the yellow/black on the Main relay right? Presumably supposed to read something like 10-13 ohms, if it's significantly higher or infinite, the wiring must be faulty there somehow?

That seems like a good Idea. The weird thing for me is why did it work fine since march? I guess thermal expansion and whatnot could explain it, especially if it's loose connectors like you hypothesize. It's definitely temp related though: today it started and idled in the afternoon, but then would only run for like 2sec in the evening after dark. (I guess why is irrelevant at this point, beyond curiosity.) Do different injectors have different connectors or are they just potentially faulty? I had the impression they were fairly universal.

Oh, also: ezone, if you remember helping me with my suspension issue: turns out, a big part of my problem was that the firestone I went to for the alignment didn't tighten the adjustment bolts down on the UCAs, so the camber could just flop around. I only found out when I heard one of said bolts fall off the car. Literally all 7 of them that were left were like finger tight. That's what I get for assuming, I guess.

ezone

The PGMFI main relay contains two separate relays inside. One feeds power to the ECM and many engine components, the other powers the fuel pump.
But the ECM has multiple power supply circuits sources and ground circuits.

Bingo! Only I was thinking of the female pins in the injector harness connectors as being the likely culprits, but yeah that would test the complete circuits ---because I thought you said the injectors already ohm tested ok. (Did you test them when hot too?? GMs injectors used to short the windings mostly when hot.)

It wasn't broke then.
Now it's broke.
Most broken stuff doesn't heal on its own.


When you figure out the problem, you may have the answer.


srsly, idk.
*facepalm*

Zealot Prime

So I finally had some time to work on the car and figured out why it wouldn't start. Turns out it was a whole lot stupider than I was making it out to be.

When I started to get into the driver's footwell, I was reminded of the existence of a kill switch the idiot previous owner installed. (I'm assuming it makes the car super impossible to steal, since no car thief could ever find a aftermarket toggle switch) I traced the wires on this thing, turns out it's wired to the injectors directly on one side, and to the battery on the other. Near the battery, there was homemade a fuse holder made using electrical tape. Somehow, this superior component managed to fail, and no longer contained or would hold a fuse. For now, I just replaced it with a real fuse holder and it runs again. I feel like an idiot for not thinking of that thing sooner. Now I just have to figure out what he did to the wiring so I can fix it properly.

I did experience the car cut out once or twice on the test drive though. I'm hoping it was just the stupid crimp-on battery terminal being loose. (I replaced it with one of the clampy kind.)