Help with smog (failed nox)

[tjg8675]

Hi all,

I have a 95 5.8 bronco

I failed my State of California rubber glove test(smog).

I failed the nox part of the test

15 mph max allow 683. me 1737 fail

25 mph max allow 585. me 727 fail

all other tests pass

egr - pass

pcv - pass

air pump - pass

vacuum lines sensors/switches - pass

fuel cap - pass

timing - pass

evap - pass

spark controls - pass

o2 sensor - pass

cat - pass

check engine light - pass

I have the EOER code 312 (thermactor air system/fault during engine run self test) with no check engine light (but does work)

I replaced my cats awhile back after they broke apart and plugged up, at the same time I had to replace a rubber hose for the air injection system just in front of the cat (I wasn't sure if this caused the bad cat or if the bad cat caused the old hose to melt (any insight would be appreciated immensely))

Basically I need help diagnosing which part is causing the failed nox test and the trouble code.

I personally think its (in order of fix): check valve off of (replaced) rubber tube, metal tube off of check valve, air control valve (ACV) off of metal tube.

And I think something may also be up with the idle air control valve.

Any help would be very appreciated thx

 

[miesk5]

yo Tjg,

Re; "had to replace a rubber hose for the air injection system just in front of the cat (I wasn't sure if this caused the bad cat or if the bad cat caused the old hose to melt (any insight would be appreciated immensely)).."

Someone may have replaced the metal tube w/ the rubber hose, which would def melt.

Is this Air Inlet Tube that melted? See #4 9J454 Air Inlet Tube

by Ford via thedieselstop.com

or @ PCI Inc;

Ford Air Tube

Replaces O.E. E6TZ-5F235-B

Use with #7 clamp.

Use with #39 valve

$28.14

http://www.pciinc.com/images/53.jpg

Ck all air sys Vac Lines first & since you obviously know the system, I'll skip the overview for now.

---

Next is did you do both KOEO & KOER portions of the test with engine @ Normal Operating Temperature before doing KOER?

---

DTC 311, 312, 313 & 314; "...311 and 314 indicate the Secondary Air Injection system is inoperative. DTC 312 indicates that Secondary Air is misdirected. DTC 313 indicates that Secondary Air is not being bypassed when requested. Possible causes: Visually inspect vacuum lines for disconnects in the AIR system. Visually inspect for proper vacuum line routing. Refer to VECI decal. Visually inspect Air Pump for broken or loose Air Pump Belt. Refer to Section 13A for adjustment/replacement..." READ MUCH MORE

Source: by Jim at http://www.justanswer.com/questions/sqj6-trouble-codes-fo-1995-ford-f150DTC 312 Secondary Air Injection (AIR) misdirected during

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KOER Troubleshooting

ATTEMPT TO ELIMINATE DTC 312

Disconnect vacuum line on AIRD valve (or left AIRB2 valve on 7.0L) and cap vacuum line. Miesk5 NOTE; Thermactor Air Diverter (TAD) Solenoid (AIRD)

Location pic in a 96 (AIRD) by Ryan M (Fireguy50) at fordfuelinjection.com

Key off.

Repeat Engine Running Self-Test and record service codes.

Is DTC 312 present?

Yes system ok EEC system OK. REFER to Diagnosis index in Section 13A.

No GO to KC5 .

KC5 CHECK AIRB AND AIRD SOLENOIDS ELECTRICAL OPERATION

DVOM on 20 volt scale.

Enter Output State Diagnostic Test Mode (DTM). Refer to Section 5A , Quick Test Appendix.

Disconnect AIRB solenoid.

Connect DVOM positive test lead to VPWR circuit and negative test lead to AIRB circuit of AIRB vehicle harness connector.

While observing DVOM, depress and release the throttle several times (to cycle output On and Off).

Repeat for the AIRD solenoid.

Does each solenoid circuit cycle 0.5 volt or greater?

YES GO to KC6 .

NO REMOVE jumper. GO to KC10 .

KC6 CHECK AIRB/AIRD SOLENOIDS FOR INTERNAL VACUUM LEAKS

Remain in output state DTM.

Reconnect AIRD/AIRB harness connector.

Vacuum pump connected to the supply port and vacuum gauge connected to the output port of one solenoid.

Apply 15 in-Hg (51 kPa) vacuum and observe gauge.

Repeat steps above for the other solenoid.

Does vacuum gauge reading hold for each solenoid?

Yes GO to KC7 .

No REPLACE AIRB/AIRD solenoid assembly. RERUN Quick Test.

KC10 MEASURE AIRB/AIRD SOLENOID RESISTANCE

Key off.

Disconnect both AIRB/AIRD solenoid connectors and measure both solenoid resistances.

Is each resistance between 50 and 100 ohms?

Yes GO to KC11 .

No REPLACE AIRB/AIRD solenoid assembly. RECONNECT both solenoids. RERUN Quick Test.

KC7 CHECK AIRB/AIRD SOLENOIDS FOR VACUUM CYCLING

Continue in output state DTM.

Install vacuum pump to the AIRB solenoid vacuum supply port and install a vacuum gauge to the AIRB output port.

Apply 15 in-Hg vacuum.

While cycling outputs On and Off (by depressing and releasing throttle), observe the vacuum gauge at the output.

Note: Re-apply vacuum between cycles.

Repeat for AIRD solenoid. Connect vacuum pump to the AIRD solenoid vacuum supply port and connect a vacuum gauge to the AIRD output port.

Cycle output on and off.

Does each solenoid cycle vacuum output on and off?

Yes EXIT Output State DTM, RECONNECT vacuum hoses. REFER to Diagnosis Index in Section 13A.

No REPLACE AIRB/AIRD solenoid assembly. RERUN Quick Test.

KC10 MEASURE AIRB/AIRD SOLENOID RESISTANCE

Key off.

Disconnect both AIRB/AIRD solenoid connectors and measure both solenoid resistances.

Is each resistance between 50 and 100 ohms?

YES go to KC11 .

NO REPLACE AIRB/AIRD solenoid assembly. RECONNECT both solenoids. RERUN Quick Test.

KC11 CHECK CIRCUIT CONTINUITY

Key off.

Disconnect Powertrain Control Module (PCM). Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary.

Install breakout box, leave PCM disconnected.

Measure resistance between AIRB circuit at breakout box and AIRB circuit at vehicle harness connector.

Measure resistance between AIRD circuit at the breakout box and AIRD circuit at vehicle harness connector.

Is each resistance less than 5.0 ohms?

YES GO to KC12 .

No SERVICE open harness circuit. REMOVE breakout box. RECONNECT PCM and both solenoids. RERUN Quick Test.

KC12 CHECK FOR SHORT TO GROUND

Key off.

Breakout box installed, PCM disconnected.

Disconnect both AIRB/AIRD solenoids.

Measure resistance between AIRB circuit at the breakout box and Test Pins 40, 46 and 60. Measure resistance between AIRD circuit at the breakout box and Test Pins 40, 46 and 60 at the breakout box.

Is each resistance greater than 10,000 ohms?

Yes GO to KC13

No SERVICE short to ground. REMOVE breakout box. RECONNECT PCM and AIRB/AIRD solenoids. RERUN Quick Test.

KC13 CHECK FOR SHORT TO POWER

Key off.

Breakout box installed, PCM disconnected.

Both AIRB/AIRD solenoids disconnected.

Measure resistance between AIRB circuit at the breakout box and Test Pins 37 and 57. Measure resistance between AIRD circuit at the breakout box and Test Pins 37 and 57 at the breakout box.

Is each resistance greater than 10,000 ohms?

Yes REPLACE PCM. REMOVE breakout box. RECONNECT both solenoids. RERUN Quick Test.

No SERVICE short to power. REMOVE breakout box. RECONNECT PCM and AIRB/AIRD solenoids. RERUN Quick Test. If DTC is present, REPLACE PCM.

------------

Oxides of Nitrogen readings. Oxides of nitrogen (NOx), including nitric oxide (NO) and nitrous oxide (NO2), are formed if the combustion temperatures within the combustion chamber exceed some 2,500°F. This can occur when the engine is under load. When excessive temperature conditions exist, the greatest amount of NOx is typically produced at the stoichiometric point (AFR 14.7 or Lambda of 1.0) as the engine is under a light load. If the combustion process within an engine is burning fuel at or near stoichiometric point, NOx levels on acceleration will typically read significantly higher than those measured at cruise and during deceleration. Typically, the NOx readings at idle will be 0 PPM.

High NOx Readings. Circumstances that can lead to abnormally high NOx emissions are:

Malfunctioning EGR valve miesk5 NOTE; since there are no EGR valve codes; let's skip this for nowLean fuel mixture (AFR above 14.7, Lambda above 1.0)

Improper spark advance

Thermostatic air heater stuck in the heated air position (miesk5 NOTE; prob for a Yugo...)

Missing or damaged cold air duct (miesk5 NOTE; I think this is the large tube dangling under jack area on pass. side, it is for the smog (air) pump and goes to da filter cannister then to pump...)

Combustion chamber deposits

Malfunctioning catalytic converter

NOTE. Catalytic converter intervention and NOx concentrations

High NOx readings at the tailpipe are an clear indication that there is a problem in at least one part of the system, but a NOx reading that appears within "normal" ranges or is only modestly elevated is not necessarily a reliable indicator of proper or even acceptable system performance. NOx readings at or near "normal" are possible, and not uncommon. From a malfunctioning engine equipped with a properly functioning catalytic converter. In such circumstances, truly elevated pre-catalytic converter NOx levels will be masked by the catalytic converter and the potential for an NOx problem must be further evaluated in the context of other readings of abnormal gas concentrations and AFR/Lambda readings.

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Mini-Tube Vacuum Hose Service in Climate Control System in a 96; "...Measure the length of the damaged area of the mini-tube vacuum hose. Cut a piece of standard 3mm (1/8-inch) ID vacuum hose approximately 25mm (1 inch) longer than the damaged area of the mini-tube vacuum hose. Cut the mini-tube vacuum hose on each side of the damaged area and remove damaged portion of the mini-tube vacuum hose. Dip the mini-tube hose ends in Tetra Hydro Furan (THF) or Methyl Ethyl Ketone (MEK). Either of these solvents will act as a sealer for the repair of the mini-tube vacuum hose. Insert the ends of the mini-tube vacuum hose approximately 9mm (3/8 inch) into the ends of the standard 3 mm (1/8-inch) ID replacement vacuum hose. Shake the service joint after assembly to make sure solvent is dispersed and vacuum line is not blocked internally. Test system for a vacuum leak in area serviced..." from 1996 F-150, F-250, F-350, F-Super Duty and Bronco, F-Super Duty Motorhome Chassis Workshop Manual

Source: by Ford

Vehicle Emission Control Information (VECI) Decal, Vacuum Diagrams & Calibration Parts List for 88 & UP. On-Line for Free at Ford. Click "Quick Guides" in left panel; Scroll to & CLICK VECI Labels "Provides Vehicle Emission Control Information (VECI) and a related calibration parts list." Enter applicable info (need to know your Calibration number from your B-pillar sticker). Vacuum Diagram is the same as the one on the core support or hood or air filter cover

Source: by Ford motorcraftservice.com http://www.motorcraftservice.com

 

[miesk5]

Testing For a Bad Converter; General

Source: by Rick S at http://www.troublecodes.net/articles/catfailure/

Diagnostic Tests, General Source: by walkerexhaust.com http://www.walkerexhaust.com/support/exhaust101/inspections.asp

Engine Vacuum Test

The intent of the vacuum test is to determine if there is a blockage or restriction in the exhaust system. It may or may not indicate converter problems.

Ideal backpressure levels vary from one application to another. Different size engines have different flow rates and so do their exhaust systems. Check manufacturer specifications. Readings also depend slightly on where in the exhaust system they are taken. This test can be performed using any suitable engine vacuum source, including the carburetor, intake or injection manifolds. After the pressure gauge is connected to a vacuum source, readings are noted at a variety of engine speeds.

To perform the vacuum test at the intake manifold, start with the engine off, and disable the EGR valve by removing or disconnecting its hose or one of its solenoids. Connect the pressure gauge to the manifold and take an idle reading with the transmission in neutral. Turn off the engine and disable the EGR valve by disconnecting its vacuum hose. Plug the hose. With the transmission in neutral, take another reading at 2500 to 3000 RPM. Read at variety of other engine speeds.

To perform the vacuum test at the injection manifold, start with the engine cool, and remove the air injection check valve. Connect a rubber adapter cone to the check valve connection. Then, connect gauge hose to the adapter.

As engine speeds vary, readings should initially drop slightly, then rise to within 2 to 3 inches of the vacuum level established at idle. Any sudden drop of over 10 inches of vacuum may indicate a blockage problem. Erratic swings of the vacuum indicator may indicate periodic blockages caused by loose components temporarily blocking the exhaust system.

Remember that vacuum levels are also affected by factors other than exhaust system restriction, including valve and ignition timing.

In the next paragraph they yak about "drilling or punching a small hole into the pipe in front of the converter".. anh! no way! lol, but the inlet tube Port can be used!

-

CATALYTIC CONVERTER FAILURES: by Magnaflow® via car-sound.com @ http://www.car-sound.com/04basics/04failures.asp

excerpts; "...There really is no "inspection port" for the consumer or mechanic to see an actual clog in a converter. Often, the only way to tell if a catalytic converter is malfunctioning (plugged) is to remove it and check the change in engine performance. When a clogged converter is suspected, some mechanics temporarily remove the O2 sensor from the exhaust pipe ahead of the catalytic converter and look for a change in performance.

A catalytic converter relies on receiving the proper mix of exhaust gases at the proper temperature. Any additives or malfunctions that cause the mixture or the temperature of the exhaust gases to change reduce the effectiveness and life of the catalytic converter. Leaded gasoline and the over-use of certain fuel additives can shorten the life of a catalytic converter.

A catalytic converter can also fail because of:

Bad exhaust valves on the engine

Fouled plugs causing unburned fuel to overheat the converter

­Sometimes you can tell that a converter is clogged because you don't go any faster when you push the gas pedal. Also, there usually is a noticeable drop in gas mileage associated with a clogged catalytic converter. A partially clogged converter often acts like an engine governor, limiting the actual RPMs to a fast idle. A totally clogged converter causes the engine to quit after a few minutes because of all the increased exhaust back pressure..."

 

[tjg8675]

Hi thanks for all the information you've provided miesk5

You were right about the rubber hose being replaced by someone,

I have aftermarket dual exhaust (previous owner had work done nice job, except for that hose I guess)

and yes up to full operating temperature before running tests.

Here's where I ended up yesterday

"KOER Troubleshooting

ATTEMPT TO ELIMINATE DTC 312

Disconnect vacuum line on AIRD valve (or left AIRB2 valve on 7.0L) and cap vacuum line. Miesk5 NOTE; Thermactor Air Diverter (TAD) Solenoid (AIRD)

Key off.

Repeat Engine Running Self-Test and record service codes.

Is DTC 312 present?

Yes system ok EEC system OK. REFER to Diagnosis index in Section 13A. "

Do you have this information (section 13a)? would be greatly appreciated.

and thanks again for all your help

happy 4th!!

 

[miesk5]

yo,

yw and it was a VG 4th...thanks and hope you 4th was good too.

Replace that hose with the line shown at PCI or NAPA who stocks em (as long as da cat is in same location as stock) or get the ID and get a high temp silicone hose such as those avail @ most parts place and Ford for the DPF sensors; Ford's price @ my local dealers is for $10.00 for a 10 foot long section.

I think that will help the NOX situation.

=========

I should have edited that Section 13A. stuff a lot better. That section follows that statement is Section 13A - Starting as KC 5

which is;

KC5 CHECK AIRB AND AIRD SOLENOIDS ELECTRICAL OPERATION

GL!

 

[tjg8675]

Hi Miesk5

Had a great 4th, glad yours was good also

Still dealing with this issue unfortunately, but thanks for the info you've provided so far.

I'm wondering if its possible to have a bad EGR but with no trouble code? (still have code 312 tho)

 

[miesk5]

yo,

yw

I haven't seen any no-code bad EGR situations yet. But who knows? Since EGR codes are directly related to specific component/vacuum/wiring related issues

This is by Ryan M; "...This air valve allows engine vacuum to open the EGR valve. The EGR system recycles burnt exhaust gasses into the intake. This lowers the amount of fuel needed, and lowers toxic Nitrogen Oxides in the emissions. The EGR only operates at highway cruise conditions...".

Now read this;

Refuses to open (or the EGR passageway in the manifold is clogged) will allow elevated NOX emissions & may also cause a detonation problem by Larry @ A1 Car

This should set a code, but maybe it is partially open? OR clooged at the valve or in intake man ports?

=============

High NOx Readings. Circumstances that can lead to abnormally high NOx emissions are:

* Malfunctioning EGR valve

* Lean fuel mixture (AFR above 14.7, Lambda above 1.0)

* Improper spark advance

* Thermostatic air heater stuck in the heated air position

* Missing or damaged cold air duct

* Combustion chamber deposits

* Malfunctioning catalytic converter

by interro.com via web.archive.org

==========

Stuck open will act like a vacuum leak and cause a rough idle and stalling

Source: by Larry C at aa1car.com

========

Test; "...Hook up your hand vacuum pump to the EGR valve and slowly apply a vacuum. If the EGR valve is functioning then the engine should begin to run poorly and stumble. If you apply full vacuum and notice no RPM change or can’t pull a vacuum at all, then check for a faulty diaphragm in the valve or a restriction of the EGR tube, exhaust or intake manifold EGR ports. I have run across many concerns where the EGR passages in the intake manifolds become plugged with carbon and prevent EGR flow, so try to keep this in mind during testing. Repair and continue testing..." read more

Source: by engine-light-help.com

=======

take a look at the vacuum line at the EGR Valve Position sensor (EVP) - could be leaky - leaks intermittently due to temp variations from Engine running, etc.

look here at the sensor pic

http://fordfuelinjection.com/?p=10

"...This sensor mounted to the Exhaust Gas Recirculation Valve (EGR) monitors its position. The computer delivers less fuel and more spark timing when the EGR is open. Lowering fuel mileage and tail pipe emissions..."

thanks to Ryan!

=============

COMPREHENSIVE articles; see all Ford EGR Valve Topics; Note, site won't allow you to return to this page Source: by tomco-inc

will be back Tues..hope it goes ok

 

[tjg8675]

*%!@#$* o2 sensor!

passed rubber glove test

15 MPH max 683 - me 674 (pass!! whew!)

25 MPH max 585 - me 277 (pass!! woot!)

why did the o2 pass all tests before? any insight would be helpful

thanks again for your help

 

[miesk5]

yo TJG,

I have no idea either!

That is a big quirk because the Ford EVTM does Not address the oxy sensor in any manner

I spent more time on the Code and still no O2 sensor comes up in the pin-point tests.

Unless, the Code reader didn't put-out the correct Code, etc.