Massive electrical (?) problems in over my head

[Frijoles]

Hey guys, I don't know what's going on with this car anymore.

The car was running perfectly yesterday, drove it around, came back, fine.

Today I start it up to take it to an exhaust shop and it runs like ass, if you give it gas it sputters and pops (open downpipe by the way), and the tachometer and speedo read high.

The tach, when the engine is switched off, stays at 1000 rpm. The speedo stays at 10 MPH. This is in accessory mode. When started the car will show a completely inaccurate Rev count. I wasn't able to test all the different gauges, but I will return to this later.

So, my first instinct is that I now have an electrical short somewhere. So I grab my electrical manual, and go to town.

I can't really get anywhere with it, because going by the diagnostic they give me nothing appears wrong. So I start unplugging shit hoping I get it fixed and a connector is water logged or something, I ended up unplugging everything except the dash harness, ecu unplugged, entire engine harness unplugged, etc. But the gauges still moved when the engine was off.

So I started unplugging harnesses for the gauge cluster, and I found that the small green harness on the far left front (I don't remember the Honda designated number for it) that has the blue and orange wire would make it go away. Also doesn't help me any because those blue and orange wires go f'ing everywhere.

I noticed that when this was unplugged however, the fuel gauge would slowly go from half a tank to 7/8ths of a tank of gas.

When I did run the car I didn't get any CEL, but I did confirm the CEL works. I firstly assumed that it rained and my ecu got wet so I plugged in my spare (it isn't the "right" ecu but it will work) and it still didn't work. However the second ECU DID throw a CEL.

I don't even know where to go from this. I have no idea how a massive short like this could just show up overnight like this.

Is it a short? Is it a bad ground? The only things that have been changed recently is that I installed my cooling system, bled it, and installed my blower motor and stuff getting ready to drive it. But it ran fine after I did all of that stuff.

The only thing that happened that I can think of is that it rained last night so I'm worried water got in. But where could water get logged into these wires (most of which are weather pak connectors) to short MULTIPLE things to ground like this.

Please someone help me. I will give you my phone number. Call me. Text me. I am desperate. I fear that I have angered the spirit of Soichiro Honda and he doesn't want my car to run. Every time I fix everything on it, ten more things break. I've replaced every single part on this car at least once. I took the entire dash out to fix wiring properly to prevent an inevitable electrical short and even after I do that, it still does this .

[93redcb7]

i would look at the ground on the thermostat, as that is the ECU ground

and did you check what the CEL was with the 2nd ECU?

[Frijoles]

The thermostat ground is/should be fine. The ecu being unplugged didn't change anything but I'll still check that out before I rip the main harness out of the car.

So this does sound more like a ground issue rather than a short issue?

Also, no I didn't even think to check the CEL off that ECU. My O2 sensor isn't even plugged in so I figured at best I'd just get the code for it and at worst I'd probably get an unrelated error code.

[sonikaccord]

I've ripped out the whole chassis harness...please don't go there.

I would say you have an open condition rather than a short. And it's probably intermittent, which makes life a living hell.

It's been a minute since I opened up a CB wiring schematic. It's so simple compared to the e46.

So right off the bat, check your integrated control module. Make sure the pins are clean and free of corrosion. Open it up and check the pins and solder joints.

Next, check connector C (22 pin connector), pins 2 and 4
And Connector A (10 pin connector), pin 8. This goes to the dash fusebox ground

[Frijoles]

Alright, so, still doesn't work.

I cut the hell out of my hand getting the ICU and under dash fuse box out.

The ICU looks fine. It looks brand new. I'm not sure if it's OEM because it says "made in USA" but it also has a Honda stamp on it. I'd assume it would be Denso or something if it was OEM.

Strange things today though. I have everything plugged back up now, and I noticed before I did anything that the cluster no longer shows 10 mph. It does still show 1k rpm in accessory mode. While cranking the engine the rpm slowly rises gradually from 1k to 1.5k rpm. It was starting. While running it would appear to be around 2k rpm but I could tell it was idling nowhere near that.

All of the connectors looked fine as far as I could tell. No corrosion or moisture in the lines. No frayed wires either.

While checking on the thermostat ground I managed to break off the plug to some temp sensor I think. I don't remember which one it is. It is between the single lead that goes to the speedo temp gauge and the heater hose. After doing that the car will no longer start at all, but it does try to catch.

The ecu itself is properly grounded, as if it weren't the CEL wouldn't come on to test.

I really have no idea how to even begin to tackle this.

Do you think it's possible the problem is INSIDE the plastic bit the ICU plugs into? Is that possible?

[Raf99]

You said it was an orange wire in the left harness on the gauge cluster. In your manual where does that wire lead to, just the ECU?

[Frijoles]

I believe the orange wire is for the VSS. The blue wire is for the Tach. The VSS wire completely bypasses the ecu and goes straight to the VSS. At least that's what I can gather from the wiring manual.

The blue wire probably goes to the ecu, but I'm not entirely sure.

Actually, scratch that. All of these route to the ICU before going somewhere else. But the blue wire goes to the distributor on my car.

[Frijoles]

Found something interesting.

I've been super discouraged because of how ridiculous this all was (about two days from DRIVING THE CAR LEGALLY before this happened) but I think I discovered that there's multiple smaller problems acting like one big problem.

However that's hard to say for sure, simply because some of the problems went away on their own. I love little electrical gremlins...

Anyways, the speedo and tach don't act weird anymore. They acted less weird yesterday too, but today they are almost totally normal again. Almost. The engine still wouldn't run until I fixed the plug that broke off. It still wouldn't stay running with that plug "fixed" so I swapped the wires around and it actually ran on its own. Not well, but it was running. I have a feeling part of my issue happened coincidentally because that plug was about to break anyways. Maybe I need to redo the whole engine harness or something (don't want to ).

But I still don't understand why the engine isn't running right. I tried both ecus and neither want to run the engine good enough to drive when the engine was running nearly perfectly just a couple of days ago...

[Frijoles]

Alright, sorry for the third bump, but I want to update this and hopefully get this solved.

I no longer think it's necessarily a wiring problem. If it is, I have an entire loom from a 91 Wagon, so it's a non issue.

The weird symptoms are gone, but the car still won't stay running.

It makes compression on all four cylinders.

The distributor is fine, I tested it with a new rebuilt one.

I get spark on all cylinders.

I believe I have a massive vacuum leak, but I don't think this is new. I'm pretty sure I always had the huge vacuum leak, so I don't know if this is the cause of my problem.

The problem almost definitely has to be related to fuel delivery.

Any ideas as to where I should go from here? Fuel pump? Injectors? Fuel rail? Pressure regulator? ECU?

[F22Chris]

A massive vacuum leak will make it run like ass or sometimes not at all. If you have access to it, use a smoke machine to look.

If not, WATER is the only other thing (i lied, maybe seafoam) I would use for checking. Does the car run better if you give it gas?

Try spraying some starter fluid or brake cleaner in the intake and see if it idles better before running like shit again. If it does, you have a lean condition. (Vacuum leak)

Injectors? Doubtful. Pull out a plug and see if it smells like gas, if yes, the injector is most likely fine. Fuel rail is also doubtful because it's just a tube. The fpr works off engine vacuum, so if you have a massive leak, it won't function correctly anyway.

Get rid of the vacuum leaks before you even think about touching the rest of the fueling system basically.

I'd start with the throttle body gasket, EGR valve, and plenum/lower intake gaskets if it's as massive as you think it is.

[F22Chris]

Fixed yet?