codes 94/44 influence high NOX readings?

[pudman]

My 86 GT recently failed Calif smog due to high NOX readings. Pulled codes
and got CM 34 and KOER 94/44. I cleaned EGR, EGR spacer, TB, IAC, and
replaced the EVP sensor as it did not pass the voltage reading of .25 -.67. It was 1.1. Got rid of the CM 34. Then pulled air injection tube off from back of
cylinder heads and cleaned it out. It was totally plugged. First time I've ever done this since I bought the car new in 86. Of course the heads are plugged,
but could only clean about 3 inches down. I did verify that the TAB/TAD solenoids are working properly and the bypass and diverter valves also doing what they're suppose to. So my question is.... will only fixing code 34 get my
NOX readings down? I've temporarily routed straight vacuum to the bypass valve to keep it routed to diverter, and blocked vacuum there to keep constant
air going to cats. Do you think this will get me passed. I really don't want to pull the
heads right now. Just need it to pass, then I can take my time to fix it right.
One last question....is it true that when a code 34 is present the computer
shuts down the EGR system? BTW NOX readings are about 250 PPM over max on both 15 and 25 MPH

[84GT Ragtop]

My God, 375k+ miles!?! Wow. I'm no fuel injection expert, but you're doing the right thing looking at the EGR related components. If you haven't done so already, use Seafoam in the gas tank, crank (then change oil), and through a vacuum line (I use the brake booster line) to help clean whatever other gunk exists internally. I do that and pass every time with my carbed 84.

Hey, I looked up Tujunga, CA since I'd never heard of it. Turns out you're not far from me when I'm down in Burbank on biz. It's rare that I get down there these days, but we should get together for food and booze sometime.

[pudman]

Hey, I looked up Tujunga, CA since I'd never heard of it. Turns out you're not far from me when I'm down in Burbank on biz. It's rare that I get down there these days, but we should get together for food and booze sometime.

That sounds like a for sure go with me. PM me when you're coming down

I've done the Seafoam. Actually I do it on a regular basis. I'm pretty sure it will
pass now. Just didn't want to throw money to the state for testing. I wanted to hear a word of encouragement. This is the first year it hasn't passed

[Tigger]

I had the same codes with my Saleen however I was failing for too high HC's. My heads and injection tube were totally plugged as well however, I did not remove the heads to clean it. I pulled the front accessories off the motor and pulled the front thermactor port plug on both sides and used a coat hanger and a trimmed down drier vent brush along with compressed air to clean all the crud out of the heads. Of course the rear tube has to be off as well. I had the headers off as I was doing a header swap at the time so it made it real easy to check and clean those passages as well. It was a little bit of work but saved me from having to pull the heads. It worked too as code 44 and 94 went away after that and I passed smog a couple months ago.

[grabbergreen84]

I'm guessing that you're good to go. You might pass the sniffer in some places without cats, but I don't think you could pass any sniffer without EGR.
The secondary air injection to the heads only comes into play at warmup I believe. But the secondary air being diverted to the cats upon warmup is more critical. EGR cuts HCs drastically, and I believe that the cats scrub the NOX.
If it still doesn't pass, assuming a healthy engine with all emissions equipment functioning, I'd say that your catalytic converters might have used up all of their nine lives... Are they the originals?

And as always, make sure to change the oil soon before the test, especially if it has a lot of miles. Dis the timing back to stock too. And a good secondary ignition is key as well, so if you haven't done a tuneup in a while, now's the time.

[pudman]

Tigger.... I thought about going from the front. Does the big hole go all the way thru to the back? And then smaller holes from that into each port?
Without taking the headers off I would imagine I would still get the codes
if the smaller holes are plugged. IDK... thanks for the input

I'm guessing that you're good to go. You might pass the sniffer in some places without cats, but I don't think you could pass any sniffer without EGR.
The secondary air injection to the heads only comes into play at warmup I believe. But the secondary air being diverted to the cats upon warmup is more critical. EGR cuts HCs drastically, and I believe that the cats scrub the NOX.

That's what I've heard also, but I've also read that it toggles back and forth between heads and cats depending on the signal from the O2 sensors. The cats scrub the NOX, but need oxygen to break stuff down. That's why I'm going to try running all the air back there.

If it still doesn't pass, assuming a healthy engine with all emissions equipment functioning, I'd say that your catalytic converters might have used up all of their nine lives... Are they the originals?

All emissions are intact and working, and the cats only have maybe 5000 miles on them

And as always, make sure to change the oil soon before the test, especially if it has a lot of miles. Dis the timing back to stock too. And a good secondary ignition is key as well, so if you haven't done a tuneup in a while, now's the time.

Timing is set to stock...10*. Just did tune up. Pretty much standard procedure for smog time. What do you mean by "secondary ignition"?
I appreciate your help

[Tigger]

Yes the big hole goes all the way thru. My drivers side plug came out with the power steering pump bolt. The pass side was a little harder. It took some effort but I got it out. I replaced it with a new plug because I messed up the internal threads. The ports that run the length of the head were severly plugged on my engine. I spent a good amount of time cleaning them. I did not have to unclog the holes into the exhaust ports on my car though. They were unclogged when I was done. I am not sure if they were plugged before I cleaned the long ports. All I can tell you is that a lot of crud came out of the exhaust ports when I did the cleaning.

[pudman]

Great!!! That's what I wanted to hear. I'm going to smog it this week some time.
If it passes with the air diverted all to the cats, then it's going to be awhile before I clean everything out, and plumb it correctly. I'll post the results. Thanks again to everyone for your help

Robb

[grabbergreen84]

What do you mean by "secondary ignition"?

Plugs, wires, cap and rotor.

[pudman]

Didn't pass smog today After doing above posted fixes HC's went up
6 PPM's in both MPH tests. CO is at 0.00 in both from 0.02, but NOX readings went
down 33 PPM from 1096 to 1063 in 15 MPH. And went up from 929 t0 1086
in 25 MPH. Max is 804 and 685. Pulled codes and CM 34 did not come back.
So am I correct in thinking it must be the cats? Or can having all the air
injection going to the cats be bad? Other than that it ran sooooo much
better fixing and cleaning everything. The cats must be really plugged running
so long with no air being injected. Any thoughts or suggestions?

[Tigger]

Here in Oregon, they do not test for NOX so I did not have to deal with that however as I understand it, high combustion temps are a cause. Not having the thernactor ports working properly could be why?

In my case I could not pass due to high HC's. The allowable is 220ppm and I had around 2500ppm. After doing the initial checks on the system and finding nothing, I figured the cross over tube was clogged. Since I planned on replacing the exhaust system, I decided to wait till then to remove the tube and see.

Along with cleaning the thermactor ports in the heads and the rear tube, I installed some used motorsport headers, a used BBK xpipe with cats and new O2 sensors, and a used set of flowmasters. With all that, my HC's went down to 137ppm at an idle. The car still had 3 of its 4 original cats on the factory h-pipe. I cut them off to look inside and they were not clogged or really dirty. I am not sure that just replacing them would have helped my car pass.

Below is a link to a thread that I started on Stangnet. There is some good info in there that may answer some of your questions.

http://www.stangnet.com/mustang-foru...-emissons.html

[84GT Ragtop]

So am I correct in thinking it must be the cats? Or can having all the air injection going to the cats be bad? Other than that it ran sooooo much better fixing and cleaning everything. The cats must be really plugged running so long with no air being injected. Any thoughts or suggestions?

If you have air going to the cats full-time make sure the car is very warmed up since it takes longer for them to get up to operating temp. I do the same thing you do just because it helps cut down on the unburned gas smell when I first start the car, and I failed once when I let the car sit too long after I got to the smog shop. I then drove the car on the freeway a few miles, pulled back in, and it passed with flying colors. I suppose it is still possible you've killed the cats but they've been on only 5k miles.

What I don't understand is that since yours is an 86, and hence fuel injected, why it would run so rich without throwing codes now.

[grabbergreen84]

Didn't pass smog today After doing above posted fixes HC's went up
6 PPM's in both MPH tests. CO is at 0.00 in both from 0.02, but NOX readings went
down 33 PPM from 1096 to 1063 in 15 MPH. And went up from 929 t0 1086
in 25 MPH. Max is 804 and 685.

So am I correct in thinking it must be the cats?

That's what I had been thinking, but now I'd guess that you might be running lean. That will raise HCs and NOX, along with elevated combustion temps. Is it possible that a slipped balancer is giving you erroneous timing readings?

Here are some good write ups: http://www.google.com/#sclient=psy&h...iw=866&bih=443

[pudman]

Is it possible that a slipped balancer is giving you erroneous timing readings?

After doing some research the slipped balancer is something to consider. Who
knows what my timing is really set at? How will I know if it has slipped?

[Tigger]

How will I know if it has slipped?

Put number 1 cylinder at top dead center (TDC) and see if the pointer is at zero on the balancer. If it is not at zero at TDC the balancer has slipped.

[grabbergreen84]

And how about the EGR passages? They can get clogged with crud too. Granted, the only time I ever saw this was on my old '92 which came to me with an EGR valve that hadn't worked in years. I pulled a vacuum on the valve at idle, and nothing happened.
I suppose that the EGR passages could become partially clogged, inhibiting EGR flow just enough to lower it's effectiveness, as determined by the sniffer.
Can you stall your engine at idle, by pulling a full vacuum on the EGR valve? If so, that's what you want.

I also hear "don't use premium gas for the test."

So my advice for this post is to inspect a few spark plugs for signs of leanness, and to verify your timing readings. Do you still have the Secondary Air manually diverted to the cats full time? I'd probably let EEC and the Diverter Valve return to making that decision... I think you're probably very close to being in passing condition, and need only some adjustments (as opposed to new parts) to pass.

[grabbergreen84]

Also, no one has mentioned O2 sensors. How recent are they?

And regarding the EEC shutting down the entire EGR system in the presence of the code, I'm not sure of this, but I would leave the battery cable off for an hour or so, just in case, in order to clear the computer.

And it wouldn't hurt to manually pull a vacuum on the dump valve and the diverter valve, at idle, and make sure they are working. The dump valve you might be able to hear, but the diverter I would remove the output hoses, and feel for switching with my hand. After all, those are vacuum actuated parts with a quarter century and nearly 400,000 miles under their belts!

[pudman]

I have checked the EGR by pulling vacuum, and it does stumble and basically die. I've replaced the evp sensor which did check out to be bad. That eliminated the CM code 34. The EVR is new and pulls vacuum as it should. The diverter and bypass valves work correctly. I've replaced all vacuum lines. I don't run premium gas. If I do have a lean condition... what do I look for to fix? The O2's are new but basically inaffective beings the ports in the heads are plugged. I think I'm going to just pull the front accessories as Tigger suggests and clean out the ports, and hook the secondary air up correctly. What do you mean by EGR passages? I've cleaned the valve and spacer and T/B. Also reached in and cleaned plenum best I could. I'm holding off on cats as last resort because of price. But they are probably bad from having no air injection to them. Is there a way to check them?

[grabbergreen84]

What do you mean by EGR passages? I've cleaned the valve and spacer and T/B. Also reached in and cleaned plenum best I could.

You're good there.
A spark plug from a lean cylinder will be white, instead of golden tannish brown. Rich will make them black.
Definitely clean out the passage in the heads, and also, be sure that the tube all the way back to the cats is clear.

I suspected your cats till you said how new they are, although I have also heard that aftermarket cats tend to not be as effective as OEM ones. What brand are they?

[pudman]

You're good there.
A spark plug from a lean cylinder will be white, instead of golden tannish brown. Rich will make them black.
Definitely clean out the passage in the heads, and also, be sure that the tube all the way back to the cats is clear.

I suspected your cats till you said how new they are, although I have also heard that aftermarket cats tend to not be as effective as OEM ones. What brand are they?

If I do have a lean condition what is the fix? What causes this? I would suspect a lean condition would cause high cylinder temp resulting in high NOX. The cats were
replaced 2 years ago for smog, but only have 8,000 miles on them. Have no idea
what kind they are. Alls I know is they weren't the "calif" ones. I"ve read that no air injection to the cats will cause them to plug up and foul. The tube going to them was not plugged, but with the heads being plugged who knows how the system distributes the air. Like I said the tab/tad and diverter and bypass valves are and were working properly. I've been doing hours of
internet research on my situation, but get so many conflicting ideas. You guys here are nailing things right on so I'm for anything you suggest. One last question.. can you test for plugged cats by measureing manifold pressure at idle and 1600rpm? Again I've read that there should be no difference. If there is the cats are bad.

[pudman]

well this weekend I pulled all the acc's off the front of the engine, and cleaned out the secondary air ports. Coathanger; brake cleaner; carb cleaner; compressed air, and per Tiggers method a dryer vent cleaning brush. I was able to push it all the way thru to the back, so I'm pretty sure it's clean. Air tube in back...clean. But i'm still getting codes 94 and 44 KOER test. Suggestions for what to do next? : I did only drive it about 10 mins. I'm going to leave the battery disconnected all night and tomorrow, and will test again. Will post results

BTW... She runs awesome. Crisp quick acceleration. Smooth idle. Everything good

[Tigger]

Have you had a chance to look at that link from Stangnet that I attached? It has some good info in it. jrichker seems to know his stuff. He describes how to dump the codes as well as how to check the other parts of the thermactor system.

[grabbergreen84]

You can clear the codes, by disconnecting the jumper wire or code reader, while the EEC is outputting KOEO codes.

Check the fuel pressure, for ~39# with the vacuum line off of the regulator, See what it is with the vac line on, at idle, too.

Another thing you can try, is a Cylinder Balance test. Run the KOER test, and within 2 minutes of it flashing the last code (after it repeats them) press and release the throttle. The computer will cut each injector and compare them all, and flash the cylinder number of the bad injector. This test takes several minutes. My '88 would do this test when it was still Speed Density, but I'm not sure about an '86 - worth a try though. Have you ever had them cleaned?
A bad injector will cause the other three on its bank to compensate, which is enough to satisfy the O2 sensor...

I have heard of diagnosing clogged cats through vacuum readings.

[grabbergreen84]

But i'm still getting codes 94 and 44 KOER test. Suggestions for what to do next?

Clear the codes, and try to get some driving time under it, and if those codes persist, you might consider pulling the headers, and checking the little ports in the thermactor bumps.

[pudman]

Here we go again. Took it for a good long drive...codes still there.

Another thing you can try, is a Cylinder Balance test. Run the KOER test, and within 2 minutes of it flashing the last code (after it repeats them) press and release the throttle. The computer will cut each injector and compare them all, and flash the cylinder number of the bad injector. This test takes several minutes. My '88 would do this test when it was still Speed Density, but I'm not sure about an '86 - worth a try though. Have you ever had them cleaned?
A bad injector will cause the other three on its bank to compensate, which is enough to satisfy the O2 sensor...

I have heard of diagnosing clogged cats through vacuum readings.

Did the Cylinder Balance test. Code 90 Did vacuum readings for clogged cats, and pressure did not change regardless of RPM. But then the smog guy says they can still go bad and not be plugged

Have you had a chance to look at that link from Stangnet that I attached? It has some good info in it. jrichker seems to know his stuff. He describes how to dump the codes as well as how to check the other parts of the thermactor system.

I have read and performed all of jrichker's write ups for all problems. He is one
knowledgable man. There probably wouldn't be any Mustangs left if it wasn't
for him So I thought I'd start from the beginning again. Hooked a
hose to the ports in the back of the heads and blew compressed air, and all is clear. Rechecked operation of both valves and tab/tad, and everything works as it should. So now I'm ready to run the KOER test again, and the fuel pump decided to not prime when turning the key on. So i'm basically forced to put the codes on hold and chase down this new gremlin. I guess I'll start a new thread for this problem if I get stuck, but any suggestions are welcome here. I'll update the codes 94/44 problem ASAP.