First some details about the car:
95 Civic EX coupe, turbo-charged, manual trans., 133,000miles, built D16Z6 engine only has ~14,000mi on it, turbo has ~5,000mi, 440cc injectors, CAI, no cat.

There’s a lot of detail here, so please bear with me. I haven’t been able to get much help on this issue from my usual sources and this is kind of my last ditch effort to prevent this from ever happening again. I’ll say “Thank you” in advance to anybody that has some info what happened.

So I'm driving to work Tuesday morning, and it's especially foggy and there's LOT's of dew/condensation everywhere. I don't know if it rained or not but I'm going to assume it did because I just washed the car the day before! Got out to the car around 6:20am and started just like any other day. Drove about 7.5mi and as I was coming up to a stop light, the CEL came on and the engine idle got really rough. Freaked the hecked out of me. It felt like the idle was going to drop so low the engine would stall, but it didn't. First thing I thought was, "****ake. Fuel pump is dead. Wait...no, that wouldn't make sense." Then my biggest fear - "Oh no...this feels a lot like when my 94 LX sedan lost compression on the #2 cyllinder. But there was no CEL for that..." Lots of possibilities started racing through my head, followed by a frustrated "WTF." It felt like the longest red light ever! Finally get the green and as I started to pull away, there was absolutely NO power and the car was shaking/lagging/surging from the bad idle. It wasn't a really severe shaking but it certainly wasn't subtle either! I was able to pull into a gas station near where I get on the highway, and as soon as I did, the problem went away - engine idle smoothed out, rev'ing sounded good and clean, but CEL stayed on. So I back up, pull out of the gas station - rough idle and no power again! I thought, "Screw it. I need to get to work." I was able to make it to work, though a little late.

One thing I noticed was that my Tenzo air/fuel gauge wasn't working (more on this later.) Once I got off the highway and drove past a nearby high school, the idle returned to normal, power came back, and the Tenzo air/fuel gauge worked fine.

Now here’s where it gets really frustrating – I had a couple minutes around 11am to run out and see if I could get the code information and see if the car was still acting up. Car started up fine and idled fine, no CEL showing. Took a spirited drive around the parking lot - no problems. Frustrated, I ended up leaving work early to try and take care of the problem at home. Car started up fine but as soon as I got out onto the street, the CEL turned on and the rough idle/lack of power came back. Bravely (or stupidly) got it onto the highway and limped it a few miles, then suddenly it started working fine. Lots of power, smooth engine, no shaking. Then it gradually when back to no power/rough idle. When I got onto the surface streets, the car performed normally once more, then quickly went back to struggling. It seriously feels like I'm driving a Geo Metro of Toyota Tercel…or a lawn mower.

A couple other things I noticed driving on the highway - When I would let off the throttle and coast a bit, everything seemed to smooth out. Still had a rough idle at stop lights though. I also noted that the Tenzo air/fuel gauge did appear to be working the whole time, it’s just that the engine seems to be running really, really lean when it's acting up. If I hammer the throttle a bit, the gauge lights up to the lean side of normal. Take that FWIW.

Later that day I was able to get the code, which was a Code 16 ‘fuel injectors’. The first thing I did was pull the main relay and check all the soldering. No cracks or dry joints. Ran it through the checks outlined in the Haynes manual without any problems. That was all I had time to do that day, so the car would have to wait until the next day for further diagnosis and hopefully a treatment.

When I came home from work yesterday, I used a borrowed Fluke meter to test the injector impedance. They all they came up around 2.6ohms, which is fine for low resistance injectors (though I must admit I do not know what brand they are or if they are peak/hold or saturated, just that they’re 440cc.) Frustrated, I completely reset the ECM - pulled the primary and backup fuses, disconnected the negative battery terminal. After reconnecting everything, to my amazement the car started up fine and idled fine. Let it idle for five minutes. No problems. Took it for a quick drive down the street and back. No problems. Drove it around town running errands for a half hour and still no problems. Here’s what really has me saying “What the heck is going on?!” - After I got home, I tested the impedance on the injectors. #2, 3 and 4 tested 2.8omhs. #1 (far left?) tested first at over 20ohms, then droped to 19.5, then kept dropping. Last number I saw was around 17.5ohms. Almost seems like there is 3 low resistance peak/hold injectors and one high resistance saturated injector, but then the 2.6ohm readings I got when the engine was cold wouldn't have occurred. Later last night after dinner, I checked the #1 injector resistance again. 3.2ohms. This should be within the range of a low resistance injector but I'm not sure why the #1's resistance is getting so high during normal driving. It would seem heat is causing the resistance to rise.

The car drove just fine today coming into work. I plan on changing the fuel filter (pain in the butt to do) and then running two cycles of STP Fuel System Cleaner. I also plan on replacing plugs and wires with NGK Iridium IX, Vision Motorworks Iridium racing plug wires, new cap and rotor. I’m sure all that lean driving must have fouled the plugs, so I might as well play it safe and take those elements out of the equation.

I know that’s a lot of detail but it’s better to have too much info than not enough. Does anybody know what happened and what I can do to prevent it from happening again?! I’m really hoping it’s just the relay and not the fuel injectors – they’re freaking expensive!!! Thanks for your help!

 

Sounds like you've found an intermittent problem: injector #1. So if you're going to start replacing parts for the heck of it, injector #1 should be at the top of the list.

When it is idling badly, disconnect the injectors one at a time to find which cylinder is dead. Disconnecting a good cylinder will make the engine run worse, but disconnecting the dead cylinder, the engine will still run the same. If this comes up as #1 again you could swap the injectors around and see if the problem follows it, absolutely confirming you have a bad injector.

 

That is absolutely BRILLIANT! Hopefully the problem never comes back but if it does, this will be the first thing I try. Now that I think of it though, would it be advisable to disconnect injector #1 and try to recreate the problem? I think I'll try that when I get home from work.

I definitely need to replace the spark plugs regardless because with the really leaned out conditions, I'm sure some fouling took place.

 

Running lean should not foul the plugs (heck, even if they got fouled by running rich, they clean themselves-- unless it was so bad that they shorted out and won't fire any more). You should inspect a plug or two before buying replacements (save your money for a new injector).

Inspecting the plugs is another way to identify a dead cylinder. If one plug looks a lot different from the others, something "special" is going on with that cylinder.

 

Checked the plugs yesterday. Everything looked good except #1 was a little more rounded than the others. They're getting replaced anyways. Pulled the P2 plug from the suspect injector, started the car, and as far as I could tell, recreated the problem exactly. I didn't take it for a drive down the street but the idle felt the same, and it took the same amount of time for the CEL to come on. Same error code too.

Also figured out the injectors are 450cc blue tops from a turbo Eclipse/Talon circa '91, so I was able to purchase a new one for $35 shipped. Any time I can fix a problem on my car for that cheap, I consider it a victory. Of course, there is the more valuable victory of the information gained from searching, reading, and asking questions. I feel like I know the fuel system, injector circuit, and its weaknesses pretty well now!

Thanks for your help!