My D16z6 is having low-end sputter issues and smells of unburnt fuel. seems to be running like poo up until vtec kicks in and then takes off like a bat out of hell. (feels like a shot of NOS). i've been throwing money at it trying to make it run right and nothing's working. also went to a honda meetup and got some ideas for more money i could throw at it, but none of their ideas worked either. the guy at the auto parts store says that he had a 95 with the same symptoms (he even imitated the sputter...cute), he threw a few grand at it and then finally gave up and parted it out. i love my civic and want it to run right.

here's what i have:
93 civic ex w/ d16z6, dc 4:2:1 header, aem CAI, straight-thru catalytic converter, aem fuel rail

here's what i've tried so far:
.main relay
.cleaned the IACV
.cleaned the MAP
.replaced the fuel filter
.replaced the plugs
.replaced the plug wires
.distributor, cap, rotor are all under 1000 miles
.timed it and re-timed it....like 12 times now
.pcv valve
.pcv hose
.full cleaning of the throttle-body
.fuel return vacuum-assist diaphragm thingy (not sure of its name)
.fuel pressure regulator
.head gasket was done about 300 miles ago (inspected the engine for wear too... looks ok)
.noid-lighted the injector plugs (they're ok)


any ideas?

 

Any CEL codes?

Does unplugging the O2 sensor eliminate the problem?

Are you using properly gapped NGK spark plugs?

Did you adjust the ignition timing like this:

 

no engine codes. (had it throw a TPS code 4 once, but that was because i forgot to plug the iacv back in... i cleared it, plugged iacv back in and it never threw a code again)

o2 sensor was installed in may. i will try unplugging the o2 sensor and see if it helps. i will be upset if the brand new o2 sensor is already bad.

yes, timing was done with the little jumper thingy. i've had my glovebox out to do the timing so much that i have considered installing a switch to close the circuit on those 2 wires so i can just throw the switch when i want to mess with the timing. this started while the timing was still retarded 2 degrees for smog, i adjusted it to 2-degrees advanced and still had the issue. i then put it exactly at stock

spark plugs are bosch platinum, had the NGKs in there previously, suspected the spark plugs initially, changed them out. yes, they have been properly gapped AND i re-checked the gap again since then. also smelled the plugs, they don't have any funny odor or carbon buildup or anything. once i figure out what the issue is, i'll probably put the NGKs (that aren't that old anyhow) back in.

update: unplugged the o2 sensor and took it for a spin to the end of my road.....other than the engine light coming on, no changes.

 

You might want to measure the fuel pressure (with and without FPR vacuum hose attached) and compression test the cylinders.

 

ok, so today i went to compression test the cylinders and my number 3 injector started pissing fuel all over my engine compartment from where it sits in the fuel rail. i went up to the dealership and got a new injector seal for it and the sputter knocked down to where it sputters up to 2.5 krpm (as opposed to 4k-5k where it was stopping before). while i had the fuel rail off i noticed that a few of the other injector seals dont exactly look great....i picked up the other 3 and swapped them in. now it sputters to 2krpm before it catches up with itself.

broke out the can of starting fluid and started spraying all the vacuum lines, the injector seats, the ends of the lines, everywhere that i figured i might have a vacuum leak that might be detectable in this fashion. no dice. might just wind up buying braided steel fuel lines and replacing every damned hose under that hood. (at least it will look pretty)

 

as an epilogue... it was a faulty rotor in the dizzy.

 

Well at least you got a whole bunch of parts and cleaned things and checked things you prob wouln't do on a normal day. And this is also great info on what to check for if this happens to people. Unluckily at your expense. : (

 

Makes me want to do my rotor lol.

 

OEM or aftermarket? What brand?

 

can u elaborate on your meaning of faulty? I beleived my oem one was no good so I purchased a new oem one along with an oem cap that had visible signs of wear on the contacts. After I opened the bag, I compared the two rotors and the used one was the same except for carbon on half of it.