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Discussion Starter · #1 ·
Performed compression test on the culprit cylinder and my friend had me stop cranking at 155PSI and said it was still building. So compression's good. Adjusted valves, still a little clatter at certain RPM but don't think this is causing my misfire; also changed spark plugs after the valve adjustment. New set of plugs made it run "like new" for about a half of a day, really smooth purring revs and no jerking or stuttering on acceleration - then back to the same stuff, clearly a dead/barely firing cylinder. All other cylinder spark plugs appear to have normal combustion, no soot. Cylinder # 3 plug was covered in soot after a single drive to work.

Pulling the spark plug wire from this cylinder with engine running has little/no effect. Pulling the injector above this cylinder seems to change speed of the engine for a second, then it settles back down.

All other cylinders working normally and pulling their plug wires causes engine to misfire even more.

Cylinder # 3 has strong spark as evidenced by a spark tester being hooked up to the wire; additionally, when lowering wire down into cylinder head you can hear the sound of the spark arcing to the plug/walls before its fully inserted onto the plug. So spark is good.

Injectors are cheap rock auto purchases, Ultra Power brand I believe, paid $32 each. Engine has new harness and a fresh manual trans ECM was installed.

Only codes that come up are fuel supply system (comes on when I arrive at work and is generally gone by the time I get back home.) Code 16 fuel injector system, pretty obvious where this one's going, but doesn't come on/stay on unless the cylinder is literally DEAD with no combustion whatsoever for a good while. Also have code 10 IAT, intermittent.

Suspecting the injector over this cylinder I pulled it from the rail; hooked up a handheld pump to the injector's top opening and pushed ATF into the injector. While pushing ATF into the injector used electronic injector pulse tester to command the injector to pulse rapidly. It did so for about 3 seconds then slowed down and clicked quieter. No "spray pattern" or squirting from the injector during this time - only slow drips of ATF.

Is it safe to say this cheap-ass injector is done and just needs to be replaced with a quality reman?

Only other thing I can think to do is move the injector over to the next cylinder and see if this misfire travels.

Any advice or ideas appreciated, thank you!
 

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93 4d lx, z6,ported, port matched, compression bumped, balanced, manual swap
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Pull the rail, secure the injectors in with zip ties, remove spark plugs and ground the plug wires, crank the engine and watch the #3 injector, I bet it's a wide wide open fire hose. Spend the 260 for a set of flow matched stock injectors, you won't be disappointed.
 

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4d EG manual rack/trans low n slow
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my money is on fuel injector as well, the soot on the bad cylinder is a bit of a give away.
To confirm it you can swap the injector to another cylinder, and if the issue follows it, you know for sure its the issue.
Especially if its not doing it all of the time.
 

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93 Civic HB SI, 95 Civic HB CX
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Check resistance of the injectors with a multimeter. To set injector codes, those damn things must be wayy out of spec.

You want to make sure you're not subjecting the ECU injector drivers to a resistive load that could be damaging to them. Higher resistance isnt going to be damaging, and will set ECU codes if it gets high enough, but low resistance will damage things. You want to make sure where you're currently at to prevent damage.

Also, if the engine feels like its misfiring all the time, and you suspect that cylinder is not getting fuel, pull the intake boot and give the throttle body opening a spritz of flammable brake clean or throttle body cleaner, not too much to overwhelm the cylinders already getting a fuel supply from the injectors, but just enough to richen things all over. It will draw in the vapor from the spray cleaner, giving the fuelless cylinder a source of fuel so it can begin contributing power with the rest of them.

If that cylinder really is misfiring due to lack of fuel, you should notice an immediate change or smoothness to the engine when it gets the fuel from the external source. This is direct confirmation that you are losing fuel supply to that cylinder for some reason, and need to focus your efforts on getting fuel back there.

If injectors spec bad doing resistance checks, replace them, but buy good ones to go back with! Even used OEM ones from a junkyard are better than the ones crafted from Chinesium.
 

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Discussion Starter · #5 ·
Ohm'd all of these cheap ultrapower injectors out and all were within spec - 10-13 ohm. While swapping over pressure regulators to fix my fuel supply code issue, broke bolt off in the rail. Currently waiting on a new OEM fuel rail and a set of flow-matched OEM injectors to go with. Will update when it's put back together.
 

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Discussion Starter · #6 ·
Installed new OEM rail and new flow-matched injectors. After everything tight fired up and still had the exact same misfire on cylinder # 3.

BUT CHECK THIS OUT - WTF : Frustrated I started messing with all the plug wires, while engine on. Cylinder # 3 ACTUALLY FIRES (RPM smooths out and engine sounds much better) - ONLY WHEN the plug wire is held JUST ABOVE the spark plug, rather than fully inserted on top of it. Fully inserting the plug wire onto spark plug causes the misfire to come back. Lifting it up SLIGHTLY causes misfire to go away as cylinder begins working - lifting it up too far obviously causes cylinder to be dead again.

WTF??? Tried swapping over another plug wire I had laying around and exact same issue persists. Do I have some kind of mystery grounding issue going on?!

Any help appreciated ; this thing is blowing my mind right now.
 

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BATSLOMAN GIVES NO FUCKS.
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pull the spark plug out and replace it, could be shitty ceramic
 

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Discussion Starter · #8 ·
Woah, seriously almost forgot my basic engine knowledge there for a second, haha.

Pulled cyl # 3 plug, of course fouled - I never replaced it after correcting the injector problem.

Swapped in a brand new NGK plug and it's back to running on all 4.

After a spirited drive around town it's not trying to slip back into 3 cylinder mode, either.

I guess it's fixed, y'all - still wondering if it really was the injector that fouled this cylinder out so badly, but fingers crossed?

Thank you everyone for your input. :)
 

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93 4d lx, z6,ported, port matched, compression bumped, balanced, manual swap
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I'm pretty sure it was the injector, lifting the wire changed the temp of the spark just enough to get that fouled plug to fire, if you had held it like that long enough for the plug to burn clear it probably would have flaked that ash off and been fine.
 

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Discussion Starter · #13 ·
Changed out the oil last night; was thinner than I'd like and smelled of gas, go figure. Changed to a nice synthetic blend 5-20 and new filter.

It took me to work today with no issues, plenty of power, very smooth running engine now too. It definitely needs the valves adjusted again - either I got sloppy with my first adjustment or the motor wasn't cold enough, the obnoxious clatter at light throttle is back full force.

My friendly IAT code hasn't popped back up on the dash lately either - CEL has been completely off. The nasty fuel sup system and injector codes are gone as well.

HOWEVER I've discovered something new - I was really playing with it today and tried a WOT 1st gear pull to see if I could get this D15 to bang the limiter and it cut off HARD at 4500-5000RPM. Sort of like the fuel pump cut out for a split second. After letting off, back to normal. I suppose I wouldn't have noticed this taking it into work, it cruises at a comfortable 3000RPM in 5th gear.

While reassembling the fuel system with a new rail and injectors I decided to not bother with my "new" fuel pressure regulator that was supposed to replace my AEM FPR. The stock bolt flanges interfere with the housing of the new fuel pressure regulator and don't allow them to tighten down flat (probably why I broke the bolt off in the beginning). The questionable AEM FPR is on my rail now and I wonder if it's causing fuel to return to the tank under high demand.

Or maybe I should just swap in a new pump while I'm at it? All of this driving with a dumping injector must have overworked the pump, I suppose. My pressure gauge mounted to the fuel filter reads 31PSI at idle with vacuum line plugged into FPR. Is pressure going to read different @ rail vs @ filter?
 

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92 Civic Si
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Crappy injector sticking open, fouling the plug. Prolly clears out with lots of revs.
Other thoughts, how does the the t-stat ground look?
 

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Discussion Starter · #16 ·
After some searching I've just been stricken with what I might have really gotten myself into.

The block stamp says D15B7. The casting number on the head is PM8-1. Something seemed really off when I adjusted valves again this morning when I was staring at the valvetrain and noticing I had about half the rocker arms that I was seeing in pictures.

I think I have a D15B7 with a B8 head.

How screwed am I if I need this thing for a daily driver? I'm doing research and seeing that the CX head makes less power? And I just installed a civic DX ECM and DX injectors. I guess this would explain the early fuel cutoff?

Only codes currently active are 10, 14, and most recently 1. Otherwise car drives fine and does good on gas.

I don't know the history on this motor or what was done to it really before I bought the car, just that it had "been gone through". Under the V/C is crystal clean.
 

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BATSLOMAN GIVES NO FUCKS.
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D15B71992-1995Honda Civic DX,LXSOHC 16V I4235

D15B81992-1995Honda Civic CXSOHC 8V I4180
last box in that is your injector flow rate
 

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Discussion Starter · #18 ·
D15B71992-1995Honda Civic DX,LXSOHC 16V I4235

D15B81992-1995Honda Civic CXSOHC 8V I4180
last box in that is your injector flow rate
Aren't all 92-95 civic injectors interchangeable? Ecu determines pulse width as well correct?

A work friend gave me a chipped p28 obd1 ecm. I also have a chip programmer on the way that uses Crome. Using these tools can I set the fuel mapping up to run this motor right? I'm also reading the CX motor usually runs a 1 wire o2 sensor. My engine is currently running a 4 wire.

The only real driveability issue currently is that it pings under very light throttle. (Thought this was valves at first) Otherwise accelerates normally and has OK power.
 

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93 Civic HB SI, 95 Civic HB CX
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Aren't all 92-95 civic injectors interchangeable? Ecu determines pulse width as well correct?
Nope, they are different.

Pulse width is just a representation of on/off time.

Volume dosed is tied to pulse width, static injector orifice flow capability at a given pulse width, and fuel pressure.

When you have a programmable ECU like @Oldcivicjoe said, you can simply rescale the stock map you pick, to use whatever size injectors you want. The ECU can simply scale the pulse width to compensate for changing orifice sizes, up to a point. The injector flow rates you are talking about can be handled by adjustment of pulse width alone, making a 240cc injector act like a 180cc. To do so, it will simply run less on-time.

If the ECU is stock, the pulse width its going to use to run an injector is specific to known orifice size, fuel pressure and base flow rate at a given pulse width. Meaning, you need to run the injectors that a stock ECU has been tuned by Honda to use.

Otherwise if you run smaller injectors, the progranmed pulse width the ECU is programmed with will control the injector yes, but will effectively inject less overall fuel, causing it to run lean.

Vice versa if you were to install larger injectors without telling the ECU you've changed orifice size, it will run rich for the same pulse width.
 
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