Failed Smog: high HC, high CO, very low NO

[Explorer94XLT]

I've been trying to pass emissions for a while now. Things I have recently replaced: thermostat, O2 sensors (4 wire type), spark plugs & wires, fuel filter, air filter, motor oil, and CAT. The cat was the direct fit (bolt on) model by Magnaflow.

Before I changed the CAT...
@ 15 MPH: HC 96 ppm (max 61); CO% 1.83 (max 0.43); NO ppm 29 (max 350)
@ 25 MPH: HC 90 ppm (max 61); CO% 1.99 (max 0.43); NO ppm 21 (max 350)


After I changed the CAT...
I don't have the exact numbers because the technician ran the test for free but essentially the results were pretty much exactly the same. I was watching the screen as the test was running.


This crap is discouraging but I'm not giving up. The vehicle seems to run great otherwise. It's a 2WD '94. It's got a 4.0 L engine and the odometer reads 180641.
I'm bummed out and at a loss for what to do.
Please help.

 

[sport97]

Just a thought, was the engine warm or cold when the test was done? I believe the computer adjusts air/fuel ratios depending on the engine temp. That might throw emissions off.

 

[Explorer94XLT]

I tried to get the engine as warm as I could. I drove it on the freeway for about 8 miles before I took it in for the smog inspection.

 

[sport97]

I tried to get the engine as warm as I could. I drove it on the freeway for about 8 miles before I took it in for the smog inspection.

Ok, that is probably warm enough. I was wondering if maybe it had sat overnight at a shop before being tested. Hopefully someone else can chime in and help you out. Goodluck!

 

[mr2fix2it]

I see a few things here .First off the nox is already low a cat would make no change thats what it affects.The high other readings are possibly from a dirty MAF sensor due to the fact that it raised co and hc went down I would try cleaning that and look for small build up on maf sensor elements or if you have a new one you can try that Good Luck.

 

[Explorer94XLT]

A new MAF is $79.99 + $60 core so I'll try cleaning it first. OK so to clean the MAF do I spray it with carburetor cleaner?

 

[FIND]

are you using gas blended with ethanol for the test or regular gasoline?

 

[cybergasm]

Well before you start throwing more parts this.....

What is the condition of the engine ? besides "it runs great" Have you check the compression lately? know any history of the motor?

Surmising with 180k and change that although the motor is running great but it might be getting alittle tired. Could be possible you are getting alittle oil past the rings and into the cylinders or maybe a head gasket?

Just some food for thought.

 

[Explorer94XLT]

I fueled up at a Shell station about 3 weeks ago with 89 octane. I'm not sure if it was regular gas or not. Around here they add 10% ethanol to the fuel during certain months of the year. I'll have to get back to you on the final answer for this one.

History of the vehicle: I don't have the Carfax but here's the story in short. My dad bought it used around 2000 so and it was a one owner vehicle at the time. Dad got this 2WD explorer to tow his sailboat. I've had it since about 2004.

It doesn't emit any kind of smoke from the tail pipe and it doesn't have a sluggish accelleration. I really don't think the head gasket is blown but you are right, it's getting up there in mileage. It wouldn't hurt to check. Dad has a cylinder compression gauge. I'll do a compression test on it and post the results for you folks on here so that you have some details to work with.

 

[huntman58]

Sounds like you may want to pull codes from it first off yes there may not be any that have set the CEL but there still can be some waiting in the wings to do just that. Also you may not have any codes with KOEO but with KOEO you may so do both test and see if you’re getting any codes. Then if you are trace them down and fix the reasons for them. just remember because a code says a bad O2 always lean that dose not always mean you have a bad O2 sensor it can be a vac leak , dirty MAF or many other things. Also when is the last time the plugs were changed, wires, air filter, things like that. Same with an oil change they all should be done before you go for a smog check. I try to do them a few days before but not more then a week.

I live in Calif and have a 93 x 4x4 with over 225,000 miles and it so far has passed almost every time but once when I did have a bad cat some ten years ago now. We also have the super enhanced version of a smog check here one of the hardest ones to pass.
I will say I am just under the gun on the NOx part but before I run it in next year I will be changing the one universal cat out for the stock ones that are CARB and Calif approved. I have to do that as one it’s not working well any more because of the truck running rich for to long and 2 it never did really do that good of a job but it got me passed before then went to this new test system. I also have passed with a small miss but the list I gave you I do every time before I take it in well okay every two times I change the plug wires so check things out and look it over but start with pulling any codes first then go from there

also try searching this link here

How To: Pass Smog Inspection ( California)

 

[huntman58]

Just a note to my other post I had a universal cat installed here in Calif about ten years ago last time slogging it they almost failed me for it and thankfully I still had my recite for the thing . the Tec even called Sac to confirm that it was still legal to pass me with it that’s how tight there getting in some areas so best not to play games with it and make your fixes and adjustments right and use parts for your car nothing other any more. Just a FYI for ya

 

[Tbars4]

...Here's a pretty handy link for you...Read the links at the bottom..:biggthump
http://www.smogtips.com/failed-emissions-test.cfm

...It's from this thread..
http://www.explorerforum.com/forums/showthread.php?t=219411

 

[Explorer94XLT]

huntsman58- I don't know what a CEL is, nor do I know what a KOEO is. I guess I have some reading up to do.
EDIT: It just occured to me that CEL is Check Engine Light- Duh
EDIT: KOEO= Key On Engine Off......................................Ok, I got it now.

Tbars4- Thanks for the links, I'm going to read up on those too.


About the issue with the codes, I went down that road recently too (sort of). About two months ago I took it into a local service garage to have a diagnostic done on it. They recommended a complete tune up and perhaps my negative battery cable replaced. I didn't really get the type of detailed answers I was looking for and I mentioned that to them. The mechanic told me that since my check engine light was not on that the computer would not tell me what was wrong with the vehicle.

My check engine light is still not on.

 

[Explorer94XLT]

KOEF codes

OK, I read the sticky post and did the test as per the instructions.

My results: 111,111 (then 6 sec pause, separater flash) 111,111

 

[Iron Weasel]

OK, I read the sticky post and did the test as per the instructions.

My results: 111,111 (then 6 sec pause, separater flash) 111,111

111 is "System Pass" meaning that the PCM doesn't see any problems.

 

[Explorer94XLT]

But there is problem... *sigh*

The tabs are not up to date right now so I barely drive it because I don't want to get a ticket for driving an unregistered vehicle. Since the last time I disconnected the battery it hasn't really been driven very much. Perhaps 60 miles. How many miles does the computer need before the CEL comes on?

 

[Iron Weasel]

Different codes have varying conditions before they set a code. Some might only need 3 key cycles while some need 20 or more key cycles. Also, if the specific conditions of a DTC aren't met, then a code won't be stored either. Aside from that, it's not uncommon for a problem to exist, but that doesn't necessarily mean it's something that the PCM will recognize.

The high hydrocarbons could be a result of a weak spark due to having too high of a gap on some of the plugs or old plug wires with too much resistance. You wouldn't be getting a complete burn, but it's also not something that would case a code to be set. I know you've replaced the plugs & wire, just giving an example scenario.

 

[huntman58]

Explorer94xlt when you did the test for codes did you do both test meaning the one with the motor not running and then also the one with the motor running. I ask as I get no codes with the motor off but with it running I do get some codes for a lean mix on my o2 sensors for example.
I know how frustrating it is trying to get it passed here in Calif as I deal with it also but it can be done.
Here is what I do to mine from a few days to a week before I take it in if you have not done any of it then may want to look at it and see.
Pull codes both stored (motor off) and motor running if any fix first.

Run sea foam threw motor intake
Change oil and filter
clean /replace PVC
New plugs
New plug wires every other smog check
Check tire air pressures
Clean MAF
Clean Air idle sensor
Check set TPS
Check RPMs
Clean /replace air filter
Clean radiator /ac condenser /tranny cooler to make sure good air flow.
Check temp of thermostat and that it’s working.
Check all vac lines for leaks
Do fuel pressure test.

So far I have always passed doing this the one time I did not I also failed to check and do it all but then too I had a bad cat so I would not have found that one tell the test but you have replaced that already.
Also you may be running rich but its not showing as a code in the stored memory that’s why doing the KOER test helps out as it will show codes that are happing right then but not going to memory yet. Again this is how I found my lean o2 condition.

It’s a bugger to do it all but with mine if not done I do not pass but when I do it all I just slip pass ed and after all just getting it under the line gets me my tags and that is all I need so good luck.

 

[Explorer94XLT]

huntman58- I admit, I only ran the test with the engine off. I'll have to run the test with the engine running and see if I get any results that way.

I did clean the MAF
Before: It's not perfectly in focus but the post on the right front had a bunch of black crud on it.


After:



Edit: Click on the pics if you want to enlarge them.

 

[huntman58]

The MAF look good and clean that is for sure. The part of checking for codes with it running is the only way I found my lean O2 problem. for me it was part of my failing with high NOx for you yours is very low almost to low and then the others being so high really makes it look like a possible rich O2 reading and it may only be when its running like mine was but not enough to set a code.
I will say I just dread smogging my ex as every time I wonder is this the year it will not make it.
One last thought here I believe you can go down to DMV and get a temp reg tell you pass if you let them know your working on it but also need it to get parts and to get it to and from shops and to also get it tested . My nef did that for his a few times and delayed his reg almost 6 months that way I believe he had to pay all fees up front but at lest you could still drive it with out worrying about a ticket .just a thought.