Silvertune

I'm coming fresh out of the world of V6 mitsubishi so Honda's are brand new to me and the learning curve is a steep one when I have this many issues, so bear with me if you can.

The car: 1992 Civic Lx automatic. Before I owned it the engine threw a rod through the side of the block and the owner put a D16Z6 into it as a replacement (and deleted my coveted AC). That is it for modifications, it is otherwise stock and that goes for the ECU as well. He didn't swap the injectors either, they're D16Z6.

The car idles at a hair under 500 RPM's which I know is normal but if you crank the wheel when the car is sitting still the PS pump kills it. The steering is nice and light, the pump is healthy and doesn't drag like its laboring, the car just poofs out. It shakes like crazy in the engine mounts (crappy 90's torque converter I'm thinking paired with mounts being pummeled into oblivion by the below issue). Basically I think its idling like garbage even though its RPM's are normal. Its choppy and rough and can barely stay running.

The second big issue is a weird idle pulse. 1300-1400 rpm it'll just bounce "brum brum brum brum brum" (as fast as you can read it out loud). It had a major vac leak and the weird idle pulse is all it did. Now with everything sealed up the idle is within RPM range but when I'm cruising it will drop to this idle bounce even at speed unless the engine is loaded up. If I'm sitting at a stop sign with the car in gear you can feel it pulsing lightly against the shot motor mounts. The IACV and FIAV are both completely cleaned out. The one thing I can't explain is a little black valve on the back of the manifold that I can always hear sucking air. When I pull the vac line off it revs up to 750 RPM's and if I plug the line it about stalls. Otherwise is just sucks air. This problem happened BEFORE the swap, as well as now.

I obviously have a lot of reading to do but I'm suspecting an ECU issue at this moment. I want to put a P28 ecu into it so I can run it stock and eventually play with it a little bit but while I've found answers to about every other performance related question I haven't figured out how to swap it yet. I know I can convert the auto P28 to manual but simply plugging it in in the first place seems to easy.


The Mits is on jack stands right now getting buttoned up for summer fun so I need this car right now but these issues make it hard to get from point A to point B with it dying all the time in gear. I can do anything; mechanical and electrical, I just don't know where to put which pins and the name stuff yet. Any help is appreciated, I intend to keep it for awhile so hopefully I can make something of this little guy!

thisguy2012

the iac and map plugs could be switched around. i had a fresh d16z6 do th same thing

Silvertune

The plugs aren't switched, it wouldn't even run when I swapped them. I'm going to pick up a P28 next week and see where that leads me. I know the IAC's were the same per ECU but I highly doubt the injectors were.

One more issue I have is the dash lights and gauge lights don't work. Nothing lights up at all except the little orange lights behind the defrost and AC buttons. I was told by the PO that they work for about 2 minutes when its below zero degrees out then shut back off again. Perhaps a shot relay? Loose connection?

I think I have a voltage problem too because the clock resets whenever the car is idling and it flickers all the time and is extremely dim. It has a brand spanking new alternator in it though, I'm going to trace the wiring diagram and see what I can do for all the grounds.

Otherwise besides the alignment which will be fixed shortly I'm loving this car. Its so cheap and even with a CEL and running like garbage I've over doubled the mileage of my truck which ran like a top.

Silvertune

HondaPartsHero

Injectors are the same flow, 240CC

Silvertune

Are they scaled the same though? Its running absolutely pig rich at idle, almost looks like steam coming out of the pipe until the fuel trims cycle a few times and it leans back out as much as it can.

Replaced 2 main grounds and cleaned the connections on every other tonight and it runs a fair amount better. The lights still flicker a tiny bit at idle (the clock works fine now though) but I'm going to put that on my 9 year old battery (yep, 2003!). It still has the idle bounce and surges really hard at cruise. I'll just cover the gas and it'll drop into the bounce then go back up and accelerate like I'm hard on the the throttle then it'll drop back down again and the cycle continues.

Of the 14 civics at the yard today 1 had the ECU in it and it was a manual car so it looks like its time to hit up craigslist and/or ebay.

Silvertune

Just pulled my check engine codes. For some reason I can't seem to reset the light, pulling the Back Up fuse or even the whole battery does nothing (I've tried it for anywhere from 30 seconds to 10 minutes).

Codes:
10 Intake air temp sensor
16 Fuel Injectors
45 Fuel system to rich or too lean

The car runs insanely rich upon startup and idle but on the road its really lean. Like I said it has the D16z6 injectors which look different then the factory ones.

Silvertune

Can anyone tell me what this is? I don't have a service manual (or an owner's manual for that matter) and I couldn't begin on what to search to figure it out.



It's got a throttle cable of sorts coming out of the firewall. It was unplugged entirely but only so far as to make it hard to notice. I plugged it back in and my shift flare went away completely and the car shifts earlier now, much tamer at city speeds.

Also, I have a 92 so the wires for Vtec are at the shock tower but I'm not using an Si harness so when I run the wires to Vtec should I just clip and splice before the shock tower plug or is there a suitable way to add wires into the plug so it looks factory?

egsleepercivic

^ thats the cruise control

jbpnoman

Disconnecting the battery didn't reset the ECU? Try disconnecting the battery, then turning the key a couple times. It's an old computer building trick - discharges the capacitors and bleeds off excess power that the electrical system might be holding.

angrysmileyface

There are a variety of sites out there with owners and fsm. Best bet is to purchase a hard copy of a 93-95 Civic service manual from helms or on ebay. They include all 3 engines in there. Your picture as mentioned above is the cruise control.

Silvertune

Thanks guys, I'm going to go see if it works.

Nope, pulling the battery for two hours and playing with the ignition and backup fuse didn't reset a thing. When I try to pull the codes now it just flickers at me weakly and doesn't give me a readable blink.

Silvertune

Alright got the P28 in and running. The car shifts SMOOTH, the idle is smoother though it still shakes in the mounts too much. I wired up VTEC and to my pleasant surprise it works even though it has been sitting dormant for 2 years.

I also finally got to pull the check engine codes now that the ECU can give me a coherent readout. I pulled three;
Code 10: IAT
Code 14: IAC valve
Code 42: Primary Oxygen sensor heater

It still has the idle bounce though mild compared to before. The throttle progression is nice and smooth now too, with the old ecu just covering the gas was like quarter throttle. It doesn't smell like gas anymore either.

I'm going to get a new O2 sensor, the old one is ancient. I hope the heater isn't a wiring thing. I have no idea what the IAT even looks like or if it was hooked up with the new motor so I'll track that down and find another IAC to put on it.