Okay, i took my car to get it inspected yesterday and it didn't pass emissions. NJ is every two years. and last time it barely when through but did. So about 6 months ago i put a new cat and 02 sensor in it.. Figured i'd have no problems at all this time.. Well didn't work out that way. The allowable numers here for my car are .50% CO 100 HCO and 1000 NOX. Well my car managed a miserable 1.2 CO 500 HCO and about 5000NOX. WTF? It's a rebuilt 94 gsr motor, with only 20k miles on it. Like I said new cat, and o2, new plugs, wires, cap rotor, filters all around. Everything is damn new.. what is wrong with it?

From what I've read (and this could be wrong too) High CO is caused by a lack of oxygen inthe burn, so your running rich. Also high hydro carbons = rich mix. Okay.. those to seem to work together... maybe i'm rich for some reason.. but NOX.. i've read that this is caused by a lean burn and high cylinder temps. How can i be both rich and lean at the same time?

AFAIK the ECU is stock.. 94 grs ecu.. pulled it from the same car i got the engine from. Didn't look like it was tampered with at all. Stock Fuel reg.... well everythign is damn near stock. Only thing that is not are the .20 OS pistons and the .5mm os stainless valves.

Why why why? I"m so confused

 

any cels?

 

is you ecu chipped? I see these alot with the JDM engines. What kind of cat are you running?

 

did you change the timing?

 

Sorry for the delay in replies.

Lemme see. 1st. it's a 94 gsr motor USDM. not JDM. IT's not throwing any codes. The ECU as far as i KNow is not chipped. I haven't opened the ECU case, but it doesn't look like it's been messed with. THe car did past Emissions two years ago.. Engine only had 1k miles on it after the rebuild then. Numbers were about mid range of the limits then.

As far as the cat.. it's a magnaflow direct fit replacement for the engine.

Timing is still stock 16 Deg

 

Bump for more ideas

 

a second cat? i heard people failing then putting on a second and they are good

 

A second cat might work, but i'd rather not hack up my custom stainless exhaust for it and it is just a bandaid.. it doesn't help fix the problem that's causing the high emissions.

 

what kind of gas are you using?? I failed twice with 93.. I think it's the middle one (lol..can't remember). Then I used the cheap **** and pass...I guess I was running rich!!!

 

What about that emssions pass fuel additive?
Is the cat an oe or a aftermarket high flow cat?

 

I run 93 cause that is what 10.8:1 comp calls for.

Didn't try any type of fuel additive recently. The cat is a magnaflow replacement cat for the gsr. Didn't say it was high flow or anything. The honeycombs are inside.. it's not a straitpipe.

None of this should really matter.. i know guys with turbos and strait pipes that go through easy with no cat at all. Worring about the cat seems more like a bandaid fix then fixing the actually problem with the engine/mixture. WHich of course i have only guesses at what is wrong. and injectors are too damn expensive to just guess at.

 

I had high NOx on my Miata as well. After doing research the two main culprits for high NOx is high engine temps and old cat. Most NOx problems are solved by new cat and new O2.

You should try retarding your timing as much as allowed, and that will lower your NOx as well.

 

I seem to remember someone stating that you are suppose to 'reset' your ECU or computer when you make changes to the system as to allow the system to re-calibrate to the appropriate settings to compensate for the changes. Just throwing that out there.

 

well try this..... change your plugs and make sure they have the right gap.... drive your car till u need gas... put in like 89 octane(will burn hotter). also try retarding your timing... but keep it within oem spec. what all this will do is make your car runn a little hotter.....heat is what makes a cat work. plug gap is what failed me last time...

 

That makes no sense cueball. You can light off the cat just by getting the engine to operating temp or by taking a quick run down the freeway. His combustion is way too hot, that's what's causing his NOX.

Once NOX get started they cause a chain reaction and blow up into the big numbers like that. Part of the problem is that our engines don't have an EGR to keep things in check. I had this problem with my EG and it turned out to be the ignition timing. Yours sounds alright at 16 degrees.

What kind of O2 did you get? I've put brand new Bosch O2s on before and they were ****. Happened more than once. Get NGK or OEM. There's a procedure for testing the O2 in the repair manual.

Where did the injectors come from? Most of the time JDM engines injectors have been sitting for a long time near the shore and they don't fare so well. You can send them to RC engineering and get them balanced and blueprinted. I do this with all my cars regardless of any concerns about emissions. It's less than $25 and injector.

What's your fuel pressure at? Get a vacuum gauge or an aftermarket bolt on gauge and check it out.

I would also seafoam the engine. With NOX that high, you undoubtedly have large amounts of carbon build up. The carbon is part of the chain reaction that contributes to even more NOX.

 

Exactly.. theo nox just climbed and climbed the longer the car was on the dyno. And yes.. the new O2 i put in was a bosch sensor didin't think it would be causeing a problem. I put new plugs in it not to long about.. used NGK's per oem spec. Right now i have the stock injectors that were in the engine.. The eninge is a USDM not JDM. THey had 90k miles on them before i got the motor out of a car that rolled over. I don'tk now how long the car was sitting after it rolled. I'll check the fuel pressure as soon as i can get my hands on an adapter to attach the gauage.

Thanks for the input

 

I think you should try the gas and fuel cleaner idea, that me and cueball stated. I bet you 5 bucks it will work.

 

I'm not saying that the fuel cleaner and additives won't work. I'm just saying that It won't fix the problem long term.. which is what i'm looking for. I'm trying to find the ultimate cause not just patch up the symtoms to get it through. Somethng is way wrong with it and i want it fixed. I used to get around 40mpg with this engine now i'm getting down in the mid to low 20's. Something is causing it to run super rich and i've changed nothing