Might also be note worthy, when I initially attempted to start after rebuild, it struggled badly but eventually did start. Ran but very badly, misfiring like crazy and had a terrible vacuum leak, it did idle and would technically drive. I pulled the intake manifold and learned all about the air injection holes and how the usdm gasket does not work with the set up. So I "plugged" the air injection holes since my set up is running a 2 wire iacv, and liberally applied more rtv than I normally would (with trying to make sure it wouldn't squish where it shouldnt) and reinstalled with the usdm gasket since the original cork one was destroyed. From there the car has not idled since, much less moved under its own power

 

Update. Couldn't take it anymore so went back to the shop. Had 4 and 4 injector connectors switched.

• Verified every injector signal wires from injectors to ecu.
• Verified every power wire from injectors to resistor connector (bypass).
• Verified tps is putting out correct signal.
• Advanced timing slightly.

It now runs and most of the time idles pretty smooth, when I go to rev it breaks up pretty bad.
- Put new plugs and some good used wires on it.

I'm starting to suspect the coil to be a bit weak but I don't know how likely that is.
Also for the record its a p28 ecu

 

Is the coil internal to the distributor? You should be able to check the resistance of the terminals of the ignition coil to see whether it’s out of spec.

 

Its external,

• I replaced the icm with a known good one this morning
• was about to test the coil and then I decided to try to start the car.

I was back to a no start condition, getting irritated
- I sprayed a little carb cleaner on air filter and it fired right up for a second, light bulb, I pinched off the fuel return hose and she runs like a dream. Im guessing bad fpr.

 

Fpr did not fix it.
Fully blocked the return and it runs sweet, but I know it can't stay that way.
Starting to wonder if my fuel pump actually is bad now.
*At a bit of a handicap atm with no fuel pressure gauge.

 

The fuel filter might be clogged too.

 

I was literally just thinking about that. Gonna try that 1st thing in the morning. I wouldn't be so adamant about it but the kid in me screaming right now,lol. I haven't had my own hinda in about 5 years and im anxious.

 

I apologize if this is a stupid question, since I am not mechanical, but do you have all your engine bay grounds connected? and are the plugs in the distributor in the correct order?

 

Yeah the plugs are for sure. And I believe my grounds are good but honestly thats one of my issues. The car has had a wire tuck done on it and battery relocated to the trunk. the only actual ground I've found is the one on thermostat housing.

 

New fuel pump did not fix, same with new filter... while I don't know an actual pressure reading. I know it has plenty. With the return hose crimped off and it running good it blows a hole in the return. I guess its not rated for pressure. Somehow injectors requiring a stupid amount of pressure? Could a weak spark situation run better with more fuel pressure? Im running out of ideas here...

 

The injectors may not be matched to the ECU. What ECU are you using and is it tuned?

 

Its a p28, I haven't opened it up but im assuming stock, I guess for no reason. It has what I believe to be the original bluetop injectors, which ohms out to 14. From what I read that means I don't need a resistor box, even though it was running great with the box in place. Its now removed since I checked the injector resistance and found that reading. The car ran great before with the box in place but idk

 

I’m pretty sure a stock P28 isn’t a good fit for a H23a unless it’s tuned.

No idea how the car ran well before with the injector box, but if it really did, it might be a good idea to reinstall it.

 

I keep thinking that as well, I know the resistor box was working as far as testing it went. The more I think about the p28 it might be chipped, the car actually ran a bit rich and I don't think it would've with a z6 base map. Idk though. Im gonna pop the cover off asap and see.
I also keep thinking about how the only ground that is existing is the thermostat housing ground, I know that's the important one for ecu and all, but let's say it was tight but somehow a poor connection, maybe that would cause the injectors to struggle?
Triple verified physical timing, couldnt be more perfect...
Can a main relay fail in such a way? My experience with them is they either work or they dont..
There are no stupid ideas, give me anything.. lol

 

You’re right about the main relay’s failure mode.

If you want to test the integrity of the ground, you could temporarily make an additional ground with a jumper cable. Connect one end to the battery and the other end onto the engine, then see if things improve.

 

That was my next thought. Im gonna try the adding ground method for sure. And then for a full definitive test im gonna take my original supposed good pump and hook it straight to fuel rail under the hood sitting in some fuel and see.. take the entire system out of the equation to verify im even on the right track.. getting a bit delusional here, lll

 

You’re methodical about this. I know you’ll be able to sort this out properly.

 

Are all grounds in place and cleaned?
You said this all ran good before you removed the injector box and now you put it back?
You said it starts up and runs smooth with starter fluid?

 

I just added an engine ground do body, and a jumper from the ecu t stat ground to the starter ground. No change at all. The car ran amazing with plenty of power but had a bad bottom end noise. Started running bad the last day before I did a full stock rebuild. I just assumed the engine issue was getting worse but I think now it was something else. If I block off the fuel return hose the car runs great. Without it blocked im lucky to get it to start and it spits, sputters, pops, all that.

 

if I am not mistaken, both a 92 Prelude and a P28 ecu are obd1 and should have Peak and Hold injectors with a resistor box

 

Its my understanding that any obd1 ecu will run both lower impedance and high impedance. That both set ups end up falling in a similar spec once the resistor box does its thing. The ecus only job in it sending a ground pulse to fire, the resistance side of things is on the hot side.. idk.. But regardless of that, me getting 14 ohm out of each injector does mean saturated and shouldn't need resistor box correct? This is my 1st go around having to deal with it. Im gonna mount a fuel pressure gauge today and possibly wire the resistor back for testing

 

I am totally not mechanical, but did come across info on Reddit about injector plugs

 

Hmm, thats interesting. Which if you think about it, tuning wise i know to some level you can control/tune how much fuel they're getting/spraying so maybe its not just a simple off/on pulse like I was thinking. Maybe the pulse can be weak to strong. Idk. Getting a little out of my normal ability now

 

We are missing a lot of info here.
What is the engine harness you are using?
You are stating that you think the injectors are saturated due to them ohming out at 14ohms.
And you stated that prior to this rebuild the motor ran perfectly as is until you did the rebuild?

Something sounds way off with your description.
Please start of with a detailed description of what you had prior to the build and then what you did during the build with what parts and what did you touch, step by step.

 

Its been pretty detailed, but ill go over it all once more.
1. 92 si with jdm h23a bluetop swap
2. wire tucked oem harness.
3. It was already swapped and everything when I got it. It had a bottom end noise. I bought another h23a bottom end because my cylinders were hurt.

4. Full rebuild using my original head.
5. Yes the injectors all ohm to 14 which indicate that they are saturated and do not require resistor box although it was running great with the box in place.

6. I finally put a fuel pressure gauge on it an hour ago.
Fuel pressure is good.

7. Wired resistor box back in and it tries to run more with it hooked up.
I can actually force it to climb rpm and all, its just rough.

8. I am now thinking maybe the high impedance injectors running with the box maybe hurt all 4 of them somehow.
9. Im currently at my local junk yard to grab some injectors to try.
Its getting down to fearing ecu, although I have injector pulse.. I've tried my very best to document every step of the way throughout all this.

I very well could have missed something though

 

Its the injectors. I put some f23a1 injectors in just for testing, not the best fit but they plug up since I was running the bluetop injectors. Bypassed resistor box again. It cranks, idles, drives, but not 100%. Im assuming it just simply doesn't love the f23 injectors.
Best guess I have is the bluetop injectors running on a box basically burned them all up, idk. But at any rate, finally on the right track.