Hi all,
I'm hoping someone has some insight that can help me figure this out.
I've got a '93 CX hatch with the D15B8 engine and a manual tranny. 153k miles. I bought it with a blown head gasket and bad clutch, and replaced both immediately after buying it. It also had a CEL code 43. At the same time, I replaced all of the fluids, replaced the 02 sensor, PVC valve, fuel & oil filters, thermostat (old was gutted by the last owner, for some reason), timing belt, did a full tuneup, and took care of a few non-engine-related issues. I also adjusted the spark timing to whatever was OEM recommended.
Once I'd taken care of all that, the code 43 was still there, so I checked the fuel pressure -- with the engine idling, I got 36 PSI, and after shutting the engine off, it rose to 40. I checked the fuel injectors for resistance with a multimeter, and they all had the same (I don't recall exactly, but I believe it was in the teens of ohms, close to spec.)
The exhaust is aftermarket, with a header. There was a bolt missing on the cat (which, in this aftermarket exhaust, is behind the engine under the car), so I crawled under to fix that. While under there, I noticed that it had a blank where the 02 sensor could be installed directly before the cat. It was currently installed in the header, in the #4 cylinder exhaust, before it joined any other exhaust outputs. I thought that may be a problem, so I moved it to the blank after the header, and felt an immediate improvement to power, and it now revs higher before cutting out. (since this is a CX, I have no tach; I always assumed I had reached the redline when it cut out, but apparently I hadn't, because after moving the 02 sensor, it revs about 800-1k RPMs higher -- although guessing, I'd say it still only revs to 5k RPMs).
I should point out that the car runs pretty rich. I have gleaned from my research that this is caused by the CEL code, which causes the computer to run the car in 'safe mode'. So, since I thought maybe the problem was caused by the 02 sensor placement, I replaced the plugs and the 02 sensor again, as they had been sooted up from driving rich. Slight power improvement, but the CEL still comes on, although it waited about 20 minutes after starting the car to come on. On hot days, it comes on after about 5-10 minutes, and on cold days, it waits longer.
I've pulled the MAP sensor, and it looks like new. The air filter is a high-flow K&N-knockoff. I know the air filter isn't clogged (it looks almost like new), because I pulled it off entirely, and the car ran no differently.
I've run some expensive injector & engine cleaner in the fuel for the last 2k miles, to almost no effect.
Tires are good and fully inflated.

I'm really starting to get frustrated with this car. I've put a lot of time and research into it, and can't seem to get the fuel mileage over about 30mpg at best (it's usually about 22 in town, 26 on the 65mph state highways.) It's supposed to get 35-45, from all I've been told.
I'm considering that the MAP & TPS sensors may need to be replaced, and after that, about the only thing left that I can think of is the ECU itself -- but is there any way I can better diagnose this, than just to buy more parts? The manual is worthless in this respect (I've followed its steps, and basically it says only two things can cause a #43; a bad 02 sensor and a bad ECU)
I'm really tired of dumping money and time into this. Any help would be greatly appreciated.

 

I too am getting poor gas milage right now, but I think mine has to deal with the idle control. I am on OBD2 and I don't have my 2nd O2 sensor plugged in due to straight piping. A good freind of mine told me it could be my IACV.

 

Any engine performance problems?

 

Since I've never driven this without the CEL, I'm not really sure how gutsy it's supposed to be, but it drives about as I would expect, for a rated HP of 70. It cuts out as if I've reached an RPM governor a little earlier than I would expect, as mentioned above, but without a tach, that may just be my imagination. 0-60 is about 17 seconds, and down a hill the top speed is about 95. Top speed on a flat surface with a single passenger is about 80.
It idles smoothly if all accessories are off, but idles a little lower with some vibration if the A/C is on (for an engine of this size, it idles about how I would expect, with a load--but this is my first Honda, so my expectations aren't always right). It accelerates very smoothly, and doesn't cut out at all.
I'm planning to do a compression test soon, possibly this weekend if I get the time, and will post the results. I also plan to adjust the valves at that time.

 

When you measured the fuel pressure, did you test the FPR as described in the service manual.


Have you checked for a stuck open fuel injector?


The engine will run rich if there's an exhaust leak near or upstream of the O2 sensor. Check for leaks from holes, cracks, and bad gaskets.

Adjusting the valve clearance is a good idea.

 

Unfortunately, I checked the fuel pressure before I had a copy of the service manual, so I didn't know I should test the FPR. The nearest shop that loans a fuel pressure tester is 2 hours away, so I may hold off on testing that.

As far as a stuck injector, from what I've read, if you continue to have pressure after shutting off the engine, you don't have a stuck injector. (Can anyone confirm that's correct?) My fuel pressure actually rose after shutting off the engine.

I've checked pretty extensively for leaks, and everything looks pretty good. The whole exhaust is maybe 2 years old at most, and the gaskets and everything appear to have been replaced at that time... but I will check. I'm planning to pull the cat and check it soon as well, as it looks to be the only original part of the exhaust left (based on its aged appearance and a funny rattle at Idle), so I'll triple-check for exhaust leaks at that time.

 

I should mention that since there doesn't seem to be significant power dropoff at higher RPMs, I don't really suspect the cat. I've had 2 cats go bad on different cars, and other than the rattle, this doesn't have any other symptoms.

 

A rise in fuel pressure with the key off is difficult to understand. If you don't solve code 43 with other ideas, you definitely want to test the FPR.

Injectors can stick open due to mechanical or electrical problems. You might want to remove the fuel rail with the injectors and crank the engine in ON(III) briefly and then let the key fall back to ON(II) to see whether any injector continues to spray in the latter key position.

 

I still haven't checked the two things you recommended that I check (stuck injectors & FPR), but I just wanted to post an update on the situation. I adjusted the valve clearance (they were all pretty decent, but I did manage to improve them a little), and noticed that the timing belt (which I had installed about 3k miles ago) was very loose, so I re-set the timing and re-tightened all the belts. I then checked the cylinder compression, and they all averaged 155 psi with the engine cold. I then noticed that the distributor cap wasn't on quite right -- the rubber flange that allows the wires to enter the distributor was preventing it from seating down properly, so I corrected that. I also noticed that the rotor was very loose, so I corrected that -- presumably it had vibrated loose since I installed it 3k miles ago. I checked the exhaust carefully, it all looks good (no leaks). Then, after rotating the tires (my other planned project for today), I took it for a test drive to see if anything had changed. When it sat idling, it sounded better, presumably from the valve adjustment -- it never sounded very bad, but it does sound a little better now. It seemed to rev a little higher now than before (now I can reach 30mph in first gear before it raps out, which I would imagine is about what it should be), but it also idles a little lower, and hence, a little rougher. It had a hard time reaching 65mph with the A/C on, and felt like it had 1-5 less horsepower than before. After about 20 minutes running, the CEL came on. I checked it after returning home, and it was still just code 43.
I also didn't get around to checking the catalytic converter. After tinkering with it for 5 hours, I decided I'd lost enough of my Saturday to this car ;-)
I'm expecting to visit a town with a decent auto parts store in a week or two, and will rent the fuel pressure tester again then. I'll probably check the injectors this next week some time.

 

Okay, so I checked the FPR today, and these are the results: 37PSI when idling, momentarily raised to 40PSI when revving (presumably because the FPR is vacuum-controlled), and a constant 45psi when the FPR is disconnected from the vacuum, regardless of RPM. As soon as I reconnected the FPR's vacuum line, the pressure returned to normal. I would conclude that the fuel pump and FPR are functioning correctly (please correct me if I'm wrong), so later this week I'll test the injectors.

 

When I had a cel code 43 on my 93 del sol it was because I had a hairline crack in the exhaust manifold right next to the o2 sensor location. This is a common fault with civics and I replaced my exhaust manifold with a header and it cured the code problem. You say you already have a aftermarket header and you have no exhaust leaks (at pipe joints I assume). Maybe there is a hairline crack in your header that is hard to see but big enough to effect the o2 sensor measurements. Maybe remove the header and give it a close inspection and reinstall with a new exhaust manifold gasket.

 

This past weekend was spent chopping firewood, so I didn't get to look at my car at all. Hopefully I will be get some time to check that this week; I did just look for leaks at the joints, but I definitely didn't remove the entire header and check for cracks.
I did notice, though, that the CEL takes longer to come on, the colder it is outside. On a cloudy day, it took an extra 5 minutes to come on, and at night it takes about another 10 minutes. The engine temp rises just as fast either way, so it doesn't seem to be caused by a slower warmup. Does that give anyone any ideas?

 

Okay, it's been a while but I've finally gotten back to the fuel problem on my car. I had a transmission failure that took precedent, but after installing the new one, I checked the injectors and the exhaust. The exhaust looks perfect, no cracks or leaks at all. The injectors appear to be working correctly, and none are clogged or spraying differently.
When I checked the engine compression a while back, I notice that the #1-3 spark plugs were black, but the #4 looked quite a bit cleaner. Any ideas? I've bought a new cap & rotor, since the other was installed a little crooked before, I thought maybe the contacts had become a little corroded -- I'm going to install them on Tuesday, just in case.
When I was looking at the injectors, I wrote down the numbers on the side. They were MDH275 8, and on the other side JNP-065 93X. From a brief Google search, these seem like a Mitsu injector...? Does that sound like perhaps the last owner put the wrong injectors into this car? From what I've read, they look to be injecting 275cc, whereas it looks like this engine needs a lot less. I'm assuming I should replace them, but what should I replace them with? There seem to be a lot of options.

 

I've gone ahead and ordered some 195cc injectors, and have my fingers crossed. I'll post the outcome when they get here.

 

Well, I installed the 195cc injectors, and now the car won't start. I've tried disconnecting the battery, in case the computer needed to be reset, but that didn't seem to help. It feels like I have 3 of the spark plug wires disconnected, like it's only firing on 1 or 2 cylinders. I'm going to pull the fuel rail and try turning over the engine to see if they're all firing, but I don't see any reason they shouldn't be; the old injectors were firing just fine. These are what I bought: http://www.ebay.com/itm/250736615522...84.m1423.l2649
What size and kind of injectors should I be using? I'm really at a loss here.

 

Final verdict: The correct injectors for this engine, no matter what anyone says, are 220cc. I installed some (that actually say 'Ford' on them, but hey, whatever works), and immediately my CEL disappeared, and I've gotten 45 MPG on the one tank of fuel used since. It still smokes a little out the tailpipe, but not nearly as much as it did before. I'm guessing that the extra carbon buildup from running rich for so long is going to take a little while to burn off. I'll update more later if anything changes, but at this point, I think I'm home free. I'm sure this isn't a likely cause of trouble for most, but I suppose that if anyone buys a car that never gets good fuel mileage, the injectors are something you might want to check. I'm guessing the kid probably thought a bigger injector would give him more power or something, and I'm sure he's not the only one who's had such thoughts.
At any rate, thanks for the help, and I hope my troubles can help someone else :-)