Hey guys so I just got back from my second smog, first time I failed NOx only on the 25mph test. Knowing that high NOx is EGR related I cleaned the entire EGR system including the ports on the intake manifold, retest and failed on 15mph and 25mph with higher numbers than before.
Before #s: 15mph= 557 25mph= 643
After cleaning: 15mph= 833 25mph 700

What the heck!? Why the higher numbers now that the system is clean?
I put vacuum to the EGR valve and it opens.
Is there a way I can test all the EGR components and figure out wich one is not working?
I have no clue whats in the black box on the firewall that has the vacuum lines going to it but I checked it out and it seems like everything in there seems to be working but maybe not...

What do you guys suggest I do?
Thanks for all your help HT!

 

Only differences that I didn't mention about the second time around was I put 35psi in the tires vs 32 that was in it before.

 

I would try Seafoaming it. Do you have any CEL's?

 

The roller test printout shows five gases.
Post the results of both tests.

 

Thanks again for all your help! Here are the two test results

 

In both first and second tests the CO is very low at the 15MPH and non existent at the 25mph. The reason for the higher NOx at the second test is because you have improved on the EGR flow, which has compounded the original problem.

EGR/NOx is not at fault. CO is, the borderline HC is also indicative of a primary combustion issue which is a lean condition.

NOx peaks at slightly leaner running than stoich. Have a lean condition CO will drop, and NOx will go up.

Locate the cause of the lean condition issue, it could be from a weak spark, incorrect fuel pressure, lazy O2, or possibly a misfire. NOx is created due to high combustion temps, and a catalyst equipped car has two combustion events. Primary at the engine, and secondary at the catalyst.

If it's been a while since a full tuneup using quality parts then it would be best to replace all consumable parts(ignition, induction, fuel, cooling) this would help. Make sure all parameters are within spec.

 

Just changed the o2 sensor a few hundred miles ago. Haven't changed any of the ignition components in a long while but have Ngk wires and Ngk iridium plugs. Injectors are 230k old, maybe stat with a clean set of injectors and ignition components? Anything I should look into on the egr system??

 

I don't want to go overkill but I also don't want to keep chasing what is causing the issue. Is there a way I can diagnose and eliminate each item as a possible culprit so I can minimize my expenses on unnecessary part purchases? Where would you start? Injectors? Ignition? Does it seem the catalytic converter is functioning properly based on the test numbers?

 

No need to throw parts at it.
Make sure the battery has a full charge and is maintaining it while engine is running, and that component connections(power/ground) are clean and tight.
Check the fuel pressure is within specs.
Check the ignition timing is within specs.
Verify the temp sensors are within spec.
Make sure the TPS voltage change is correct when the throttle is actuated.
Verify there isn't a vacuum leak at the intake manifold/throttle body/injectors.
Verify that the MAP sensors output voltage is correct per inHg changes of vacuum.
Verify that components are not damaged or incorrectly installed.
Just good ole science.

Depending on what O2 sensor brand you used this could also affect the emissions. Bosch beer can style O2s are lazy even when new. Only used Denso, Delco/Delphi, or NTK.

 

Just checked vacuum from black box. Works according to fsm. Pulled plugs, frosted white. Looks like its running a little lean. Two of the spark plug wells have oil leaking into them from valve cover seals, not sure if this would contribute to the other cylinders running lean, I don't think so though, oil is sealed from the combustion chamber by the spark plug itself. Still not sure where I should start replacing stuff. I keep thinking getting refurbished injectors might do the trick but that's about $100 and if it doesn't do it then I'm out that $.

 

The oxygen sensor is Denso 234-4621

 

Just sent a set of injectors out to be refurbished. Wasn't to pricey and I figured it can't hurt. Also since I haven't done a tuneup in a while I'll do that as well. New plugs and wires as well as cap and rotor. Maybe a new fuel filter too

 

I would suggest that you check your fuel pressure is correct. If the FPR or Pump are failing no amount of cleaning of filter changing will do anything.

 

Cap rotor and plugs...and more important is to check ignition timing. If all checks out..and you do a pre-test and it still fails you should look at getting another cat.

 

Do you think timing belt stretch could change the ignition timing?

 

Just tested the fuel pressure. I'm getting a reading of 30psi at idle with vacuum hose attached to fuel pressure regulator which accord to the Haynes manual is on the low side but acceptible. With it disconnected it goes up to about 37 psi which according to Haynes is Low and outside of the acceptable range. If I pinch the fuel return line the pressure goes up to 50 psi or so. Doesn't seem like a fuel pump problem from what I could figure out reading the Haynes manual. Maybe fuel filter should be replaced??

 

The distributor is directly connected to the cam which is driven by the timing belt. But if the belt was loose the engine would have really bad response. Like a car that has a too big turbo, huge lag. But this is easily checked by lining up the cam and crank marks to make sure the timing belt is correctly installed. A timing light will be needed to verify that the base timing is correct.
When you pinched the hose it demonstrated that the pump/filter can create 50psi, this indicates that the pump can produce 50psi, and that the filter is not causing a drop in fuel pressure.

When you revved the engine with the gauge attached, did the pressure ever drop? If so, then the pump may be at fault.

But I think that the FPR is more likely the culprit.
EDIT: With the FPR vacuum line off see if there is any fuel inside the vacuum line or if it smells of gas. Also let the engine run for a few minutes with the vac line disconnected, see if any fuel begins to leak out of the FPRs vacuum nipple. This would indicate a torn diaphragm.[/EDIT]

To test the pump go here. It doesn't consist of a pressure test, but a volume test.
I want to say that the correct fuel pressure should be in the 40-50psi range. But I have no hard data in front of me.

 

He's within specs. However, he should check for a leak. I had a leak in one of mines..when I smelled the vacuum hose I did smell fuel so I got another one from the junkyard..even tho the accord has the nipple pointing the other way it still works fine sine they both use the same specs.

 

Would crushing in the fpr a little on the top portion cause the fuel pressure to increase or decrease? I would obviously do it in a way to not crush the vacuum nipple. I know dam owners used to do this to their own blow off valves to hold more pressure. Just don't know how the fpr work exactly so I don't know if it would make more pressure or less.

 

Trust me, you're within specs. Don't mess with it unless you smell fuel in the vacuum hose that goes between it and the intake manifold. Just smell the vacuum hose. If it's ok, then just leave it be.

It really looks like it's your catalytic converter that is the problem. I bought one recently from advanced auto. For some reason they seemed to be the cheapest. You will need a Cal Cat.

 

No. There is no way to know what you may be doing to the internals of the FPR.

If you can get an infared temp gun and see what the catalyst heat range is. Light off is 550° and maximum efficency is closer to 750°.
If the catalyst is not combustion then there cannot be a proper secondary burn.
I can't find any of my reference materials on fuel pressure specs, but I was sure it was closer to ~45psi with the FPR vacuum hose disconnected. What does Honda call for, outside of the pump volume test, with the FPR?

 

1990-1993 honda accord Haynes manual:

For 1990:
With vacuum hose attached: 35-37psi
With vacuum hose disconnected: 35-41psi
For 1991+:
With vacuum hose attached: 30-38psi
With vacuum hose disconnected: 40-47psi

I'm a 1991 so I'm out of spec according to Haynes

 

Just changed the FPR, getting fuel pressure readings of 37psi with vacuum attached and 44psi with vacuum disconnected. Hoping that was the culprit. I ordered anew distributor cap and rotor sparkplug wires and spark plugs and sent a set of injectors out to get ultrasonically cleaned everything should be getting here tomorrow, I'm planning on getting it retested as soon as I get everything on it. Hopefully I'll pass and so I can post the results here.

 

They use the same exact fuel pressure regulator. There is no reason at all why they would have different specs...

http://www.hondapartscheap.com/parts...ake-manifold-1
16740-PT2-000

http://www.hondapartscheap.com/parts...ake-manifold-1
16740-PT2-000

They also use the same fuel pump

http://www.hondapartscheap.com/parts...fuel/fuel-tank

http://www.hondapartscheap.com/parts...fuel/fuel-tank



The problem I'm having is that since you will have higher fuel pressure now in theory your hydrocarbons should go up since your car is already not even burning the hydrocarbons even tho your fuel pressure is allegedly on the low side. I hope it does pass, but if not, then it's going to be the cat that is going to be need to be changed out. Make sure you get a pretest first it will be cheaper then if you pass you can do the full test. Don't waste money if you don't have to.

 

I was thinking it was closer to the 40-45 range. Awesome
Don't get a smog immediately after the tuneup. Usually after bringing the ignition system back up to snuff, the spark will be hotter and this will burn off any residual carbon and crud, which may affect the A/F and goof with a steady emissions output.
Go for a decent drive (100-200miles)and give it a bit of an Italian tune-up before heading to the smog station to clear out any buildup.

HCs are a bad way to look at emissions. Unlike CO or O2 which are on inverse slopes, HC is a 'U'. HC emissions will increase if you are running lean or if you are running rich. Stoich is the lowest HC emissions as that is the correct balance where nothing is left over, although in reality Stoich is never perfectly maintained.

As for the fuel pressure, I was sure it was higher than his peak of 37psi with the old FPR unhooked, and now it is 44psi which to me sounds correct.
If you have the Honda or any other data which states what is the correct PSI for the CBs that would be great.
IMO the problem before was there simply was not enough fuel pressure, and the ECU would not be able to trim what is not there. If there is too much pressure the ECU can trim the injector on time down.