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  1. #1
    FEP Power Member fgross2006's Avatar
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    Default Code 46 Thermactor air is not bypassed

    I just replaced the ECT in my 84 5.0 convertible. It was running rich, backing and stalling. The code was 21 so i put in a new 1145 Motorcraft with new pigtail supplied. Restarted car and it was idling so low it picked up code 17 RPM below Self test limit. So I reset curb idle and got it back where it should be.

    Now I get code 46 Thermactor air is not bypassed. I had replaced all the solenoids, the TAB, TAD, all the vacuum tubing when I got the car around 5 years ago. i have swapped the smog pump more then once including just 2 months ago. the cardones are junk.

    I did a quick visual check and the TAB and TAD vacuum lines are intact and not broken or removed. What would cause it to not be bypassed?

    I would imagine if the solenoids were bad they would show up during KOEO or KOER. So what should I be looking for?

  2. #2

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    Well, the code says that air isn't bypassing, meaning either the vacuum lines are bad, or the solinoid is bad. Could be that the wiring is bad, I dunno.

    Every time I've fixed the smog stuff on my car, it runs worse and the emissions go up, even with new parts.
    2 1986 cougars (both 4 eyed and 5.0)
    1 1987 cougar

  3. #3
    FEP Power Member fgross2006's Avatar
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    Quote Originally Posted by Haystack View Post
    Well, the code says that air isn't bypassing, meaning either the vacuum lines are bad, or the solinoid is bad. Could be that the wiring is bad, I dunno.

    Every time I've fixed the smog stuff on my car, it runs worse and the emissions go up, even with new parts.
    well the vacuum lines were all replaced not long ago and look to be intact. I think if the solenoid was bad there'd be a different code. I was thinking maybe there is vacuum but the TAB is frozen in one state. I hate troubleshooting this feature. No room to see or touch anything.

  4. #4

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    where does that hose terminate? those solenoids on the wheel well?
    1984.5 G.T.350 5.0 CFI AOD Convertible (TRX package, loaded)
    Hooker Super Comp Shorty Equal Length Headers
    GT40 heads, Edelbrock 3721, K&N filter in stock dual snorkel,
    Comp cams XE254H, hypereutectic pistons, catted BBK H-pipe, full custom duals
    Maximum Motorsports caster/camber plates and strut tower brace, 3.73 rear.
    Firehawk A/S 225/55/16 on LMR TRX r390 wheels (street)
    Federal 595 rs-rr 225/45/15 on 10 holes (race)
    Everything else stock and fully functional.

  5. #5
    FEP Power Member fgross2006's Avatar
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    Quote Originally Posted by emerygt350 View Post
    where does that hose terminate? those solenoids on the wheel well?
    Yes the solenoid cluster on the driver side wheel well.

  6. #6

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    scary. that is the only thing the computer could know about so the 46 must be there.
    1984.5 G.T.350 5.0 CFI AOD Convertible (TRX package, loaded)
    Hooker Super Comp Shorty Equal Length Headers
    GT40 heads, Edelbrock 3721, K&N filter in stock dual snorkel,
    Comp cams XE254H, hypereutectic pistons, catted BBK H-pipe, full custom duals
    Maximum Motorsports caster/camber plates and strut tower brace, 3.73 rear.
    Firehawk A/S 225/55/16 on LMR TRX r390 wheels (street)
    Federal 595 rs-rr 225/45/15 on 10 holes (race)
    Everything else stock and fully functional.

  7. #7
    FEP Power Member fgross2006's Avatar
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    Quote Originally Posted by emerygt350 View Post
    scary. that is the only thing the computer could know about so the 46 must be there.
    The thing is that when doing KOEO test the scanner and ECM cheks all the sensors and solenoids for correct voltage and ground. thats why it clicks during the KOEO. So if the solenoid was in fact bad I would expect it to show up on the KOEO test.

  8. #8

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    but wouldnt that be the end result? not bypassing? it cant know if the vacuum operated bit on the thermactor is messed up unless it is monitoring the o2 sensor, which i kind of doubt. is possible i guess.
    1984.5 G.T.350 5.0 CFI AOD Convertible (TRX package, loaded)
    Hooker Super Comp Shorty Equal Length Headers
    GT40 heads, Edelbrock 3721, K&N filter in stock dual snorkel,
    Comp cams XE254H, hypereutectic pistons, catted BBK H-pipe, full custom duals
    Maximum Motorsports caster/camber plates and strut tower brace, 3.73 rear.
    Firehawk A/S 225/55/16 on LMR TRX r390 wheels (street)
    Federal 595 rs-rr 225/45/15 on 10 holes (race)
    Everything else stock and fully functional.

  9. #9

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    KOER code 46 is telling you the O2 sensors are seeing air being injected upstream when it should not be.
    There would be no way for the KOEO test to see that, since the air pump isn't pumping, nor are the O2
    sensors up to operating temperature.

    The diverter valve on the CFI engine is installed in an orientation that defaults to downstream when no
    vacuum is applied. So if it's sending air to the cylinder heads, either the valve is faulty (or being held
    open by bits of air pump vanes), or something is sending vacuum to it. This should not be hard to test.
    Cheers,
    Jeff Cook

    '85 GT Hatch, 5-speed T-Top, Eibachs, Konis, & ARE 5-Spokes ... '85 GT Vert, CFI/AOD, all factory...
    '79 Fairmont StaWag, 5.0, 62K original miles ... '04 Azure Blue 40th Anny Mach 1, 37K original miles...
    2012 F150 S-Crew 4x4 5.0 "Blue Coyote"... 65 coupe, 289 auto, Pony interior ... '67 coupe 6-cyl 4-speed ...
    '68 Vert, Mexican block 307 4-speed... '71 Datsun 510 ...
    And a 1-of-328 Deep Blue Pearl 2003 Marauder 4.6 DOHC, J-Mod, 4.10s and Lidio tune

  10. #10
    FEP Supporter NAVYCAT's Avatar
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    so what if the sensors are not getting enough vacuum? how much is really needed?
    2017 Mustang ECO BOOST (DD)
    1986 Capri 5.0 Silver/Red
    1969 Falcon XW GTHO coupe
    U.S. NAVY 1980-2009
    Past 4 eyes-
    4th. 1981 Capri "White" Black Magic I6
    3rd. 1984 Capri RS V8 Black/grey
    2nd. 1984 Capri RS V8 White/red
    1st. 1984 SVO Grey/grey (traded it for a worn out 1970 BOSS 302)
    Both '84 Capri's vin# were 10 away from each other

  11. #11
    FEP Super Member xctasy's Avatar
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    Its very hard to be General with Fords, Lol....


    NAVYCAT and fgross2006, I don't wanna be a "cut and shut post vvhore", but this info is found else-ware, but JACook and many others above have posted how the CFi system differs.


    Quote Originally Posted by NAVYCAT View Post
    so what if the sensors are not getting enough vacuum? how much is really needed?

    Joe, EECIV does a range of voltage only tests. Then Administers the TAB/TAD via the stock VECI pipe hookup. So its a do if true scenario.

    Like TFi ignition, Ford figured out that doing complicated timing measurement, then response was a waste of time, it was better to Administer the right decisions, then see how each falls in line. Out of range sensors happen, but its a quick flick through voltage graph that gets reported, and its then time and engine warm up cylce, close and open loop based. EECIV will suffer out of range values is certain situations.

    All tests on sensor require various kinds of pressure, temperature and sometimes resistance tests, that must be done with base reference power off.

    Measuring resistance "insitu" with a circuit powered on will give false readings and possibly damage the ECM or measurement meter. Attempting to cross check the resistance of the O2 sensors, it may damage them. The old Thexton 60 pin plug tester would do real time data capture, and the inputs are all analogue voltage changes, and its the power spectral density changes (the way the peaks and troughs are shaped).... that triggers a fault code after the digital computer does a low pass check and builds a block learning Keep Alive Memory file on it. The fault might not show up till the next KEOR. This is straight Process Logic Control stuff.


    The computer takes input from the sensors (TPS, MAF, ECT, ACT, MAP/BARO, O2 and, RPM) and the uses that information to determine when to turn the TAB & TAD solenoids on and off. No single sensor is used, it is a combination of inputs from all the sensors.

    For pre OBDII cars, the fault process is a little ropey, for SN95 Mustangs starting with the EECV 3.8, there are some 25 and 50 thou operational performance checks to keep the emissions package in operation to cut all this crap out.

    For OBDI cars (the first EECIV's from 1991 modle year, they had activated PID's); on those, you can drill down into sensor values.


    Back to fgross2006


    The MCU or EEC I/II/III/IV/V use whatever parts bin stuff FoMoCo has to end up with a compliant car that passes the 7 mile LA Basin 12 cycle engine dyno smog sniffer test.

    The TAB/TAD stuff wasn't called that until about 1979/1980/1981, with FoMoCo running a phased in parts that look the same but operate totally differently even between engines with the same VIN Code. All Fords engine codes got a revamp for 1980, and the destination of the car (Hi Altitude, Californai, or 49 States, the type of gearbox or if it was turbo didn't always change the engine code on 5.0 or carb 2.3's).

    This makes it very hard to fix a non conforming VECI set up if, say, the Air diverter valve operation is not capped or plugged the way it was when made in 1984. Or worse, that you follow 1984 California info from, say, a Thunderbird 5.0 CFi with a Standard Out Put verses, say, any other Capri/Mustang CFi HO 5.0.

    The O2 sensors and integration of the wire to the computer changed, and none of the Neutral Safety Switch stuff is the same, even though its supposed to be the same engine as a 5speed...everything is a radical hotch-potch of white box parts supplied to Ford.

    M code 5.0's and the other VIN code variants of the so called 5.0 (4942 cc Windsor design 1968 based 302)...well, they changed EVERY year, sometimes, every half year, and sometimes, each destination state.

    "Generally:-"

    FoMoCo SMOG pump (Thermactor Air System)

    This pump brings air to the back of the heads and into the two rear catalytic converters.

    When the engine is cold, the thermactor air system pumps fresh air into the heads (there are bumps in each exhaust port in the head, air goes in from the back of the heads from the cross-over tube).

    When the engine is warmed up, the air is diverted to the cats which helps to create the catalytic reaction that converts hydrocarbons and carbon monoxide into C02 and water vapour.[/QUOTE]
    Its basically like this



    Without this system, the catalytic converters risk clogging up or at least not perform as they should. At WOT, the computer tells the bypass valve to open and dump the fresh air to help limit parasitic drag on the engine. The fox Mustang’s Thermactor Air System comprises of few parts:

    Air pump
    Thermactor Air Bypass valve
    Thermactor Air Diverter valve
    Thermactor Air Bypass and Diverter solenoids (TAB/TAD)
    Check valves

    Specific only to the 165/180 hp automatic only CFi High Output 1984/1985 engines in Capri's and Mustangs:-

    Colors mine

    Black = SEFI and CFI 5.0s, and '83 4V HO
    Blue= '84 and '85 4V HO

    Quote Originally Posted by JACook View Post
    Bit of a late reply, but it bears pointing out that the diverter valve in the diagram and photo above, are installed in the
    'default downstream' orientation, where vacuum is applied to bring the air to the cylinder heads. That configuration
    was used on the SEFI and CFI 5.0s, and I believe also the '83 4V
    .

    The '84 and '85 4V used the same valve but with the
    vacuum diaphragm pointing toward the front of the engine. In that configuration, the valve is 'default upstream', and
    vacuum is applied to switch the air to downstream
    .

    Its Really easy to put 2 and 2 together...and come up with a 22 or a 4. Each is correct in the eyes of the guy adding two parts together.

  12. #12
    FEP Supporter NAVYCAT's Avatar
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    but what is the correct vacuum needed? it comes from the intake manifold but what is enough?
    2017 Mustang ECO BOOST (DD)
    1986 Capri 5.0 Silver/Red
    1969 Falcon XW GTHO coupe
    U.S. NAVY 1980-2009
    Past 4 eyes-
    4th. 1981 Capri "White" Black Magic I6
    3rd. 1984 Capri RS V8 Black/grey
    2nd. 1984 Capri RS V8 White/red
    1st. 1984 SVO Grey/grey (traded it for a worn out 1970 BOSS 302)
    Both '84 Capri's vin# were 10 away from each other

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