Hmotoredcoupe

Hello everyone, I have been searching everywhere on the forums and have become familiar with many reasons as to why my car may be failing emissions. However, it seems that no one really follows up with what fixes their problems.

I have a 94 civic ex with the factory D16Z6. It is a 5 speed manual with 148,XXX miles. Please see my results below for my failed tests and thanks in advance for any helpful recommendations to pass.

New parts in the past 2 months:
Catalytic converter and factory catback exhaust
Distributor, plugs, and wires
O2 sensor

Limits
HC - 147.0 PPM
CO - .82%
NO - 1072.0 PPM

Test 1 - New catalytic converter and catback since previous test 2 years ago
HC - 55.4
CO - .03
NO - 3037.7

Test 2 - Timing was retarded to lower NO, still not enough to pass
HC - 16.5
CO - .01
NO - 1801.7

The first attempt of test 3 involved IsoHeet to a quarter tank of gas, with the timing retarded. (This is how I passed two years ago) On the way to echeck, the car stalled and wouldn't start again. I was not getting any spark and found that my distributor had died on me. I replaced the distributor, along with new plugs and wires at this time. I set the timing back to factory settings, with the thought that if my distributor was crappy then maybe that's why I was failing. For further assurance, I had a local shop look at the car. They checked for vacuum leaks and found no red flags as to why the car would be failing. They thought it may be a bad O2. Since we did not know how old the current one was, we replaced it.

Test 3 - Timing set to factory specifications with new distributor, plugs, wires, O2 sensor, and verified there were no vacuum leaks
HC - 190.8
CO - 2.83
NO - 1858.3

While the NO did go down with the new parts, do you have any ideas as to why the other gases would increase so much? Do you think retarding the timing and the IsoHeet will lower all of the gases enough to pass? Any help is greatly appreciated!

Former User

Post the actual emissions sheets.

Hmotoredcoupe

The actual emission sheets have been attached.

Former User

Post all CEL codes.

The engine was originally only running lean, which just might mean that the fuel filter is old and clogged.

The engine is now running rich and also has high NOx.

Solve the high HC first. Did you install a used distributor or new one? What brand plugs and wires were installed? Did you set the ignition timing?

High NOx - Unfortunately, the rich condition may have killed the new cat, but do nothing there until the high HC issue is resolved.

Hmotoredcoupe

The CEL is not on. Sorry I should have specified that. Car runs fine as if nothing is wrong.

The distributor is a reman from autozone. Autolite plugs with duralast wires. Ignition timing was set with the timing light.

Thanks for the quick responses, Ron.

mk378

Did you install an OEM cat or something off of ebay?

If engine has EGR system it will clog up every few years and that causes high NOx.

If engine does not warm up to full stock temperature (190) or ECT sensor lies to the ECU and says engine is colder than it really is, the ECU stays in open loop mode and runs it rich. Make sure stock temperature thermostat is installed and working. Test ECT with an ohm meter. The IAT should also be tested with ohm meter. These sensors can get out of calibration enough to mess up the fuel mixture but not enough to throw a code.

Hmotoredcoupe

The cat was a direct replacement from Walker, part number 15800.

No egr on the 94 ex's/d16z6.

No idea when the last time a thermostat was done. This may be something to look into. Thanks.

eghatch9295

iTrader: (1)

if you replaced all of this **** and have a mechanic looking at the car, sounds like you probably hit ohio's $300 repair cap waiver. bring receipts totaling $300 or more in emissions related repairs and you pass.

Hmotoredcoupe

It's actually only 100 bucks for the year extension, and then 300 total over the year, but I want to make sure it's actually fixed for when I need to test again after the extension would expire.

Former User

Does the CEL work?

Install the specific NGK plugs listed in the owner's manual.


Regarding the thermostat, does the temp gauge in the cluster indicate that the engine runs cold?
Honda plug wires are the way to go, but start with the NGK plugs.

eghatch9295

iTrader: (1)

Waivers | Choice Plus - A more convenient Ohio E-Check program

Hmotoredcoupe

The CEL does work, but it hasn't been on/thrown any codes. I will look for the NGK plugs.

The temp of the car is always steady and normal from my experience. It sits a little under the halfway point on the gauge.

Former User

I don't see a thermostat problem here.

slomofo

iTrader: (1)

Do you have any precat exhaust leaks, broken exhaust manifold studs, or a cracked exhaust manifold? I'm guessing the answer is no, but I'm asking anyway to rule it out.

If you answered no, do you have access to a leakdown tester?


This is going to sound really crazy, but if you have a leakdown tester and 5 minutes to spare, it might be worth your while. Wait til your car is cold, like park it overnight cold. With the engine cold, do a leakdown test. Are your exhaust valves leaking excessively?

roadraceking

I would say even increase the quality of the plug. I run NGK iridiums in my del sol with a non vtec zc. NGK wires as well. Also I would change the fuel filter. But no one has mentioned that it could also be build up inside the motor. As much as I hate to use the stuff I would seafoam it and change the oil. Run mobile 1 full synthetic and a K&N oil filter. Check your PCV valve as well.

slomofo

iTrader: (1)

All I heard there was spend money on items that will make no difference whatsoever in this guy's situation.

roadraceking

How do you figure? Spark plugs are a direct relation to it not burning fuel properly. Carbon build up can cause the same thing. And suggesting seafoam is very common when passing emissions. So please tell me why you think that it makes no difference?

slomofo

iTrader: (1)

I think it makes no difference because the emissions readings dictate the car is running excessively lean.


If a car is running lean, then how do you suppose seafoam and spark plugs is going to increase the amount of fuel that goes into each cylinder?