Maf And Tb Questions

Discussion in 'Fox 5.0 Mustang Tech' started by John Dirks Jr, Jul 24, 2013.

  1. I have an explorer intake on the way. I'll probably slap on some 1.72 roller rockers too but I dont want to get into camshaft or cylinder head changes just yet. Got a full exhaust including xpipe and shortys ready to go too. Maybe an adjustable fuel regulator.

    Now, about MAF. I'll be sticking with stock 19lb injectors for now. So whatever MAF I get will be calibrated to them.

    I'll be looking at TB's too.

    My questions are;

    1) If I get a 70mm TB, must I also change the spacer to get the advantage of the larger TB?

    2) What size MAF would you recommend? (remember, calibrated to 19lb inj)
  2. A 70 on a stock intake will do nothing but lighten your wallet. The stock opening is 60 mm I beleive
  3. The Explorer manifold had a nice 65 MM TB as stock equipment. It's worth your time to get one to match the Explorer intake manifold you said is on the way.

    94-95 Mustang GT MAF - $40-$100. It is 70 MM instead of the stock 55 MM on regular stangs built prior to 94. It uses a slip on duct on the side that goes to the throttle body and a 4 bolt flange on the other. You need a flange adapter to fit the stock slip on air ducting that goes to the air box. Wiring plugs right in with no changes. *1 *2

    *1.) Metal flange adapter Buy the TR70 for $40. Or spend some time on eBay looking for one that may fit.

    *2.) MAF & sensor interchange
    The 94-95 Mustang 5.0 MAF & sensor is also found on:
    1995-94 Mustang 3.8L F2VF-12B579-A2A,
    1994-92 Crown Victoria 4.6L F2VF-12B579-A2A,
    1995-94 Mustang, Mustang Cobra 5.0L F2VF-12B579-A2A,
    1994-92 Town Car 4.6L F2VF-12B579-A2A,
    1994-92 Grand Marquis 4.6L F2VF-12B579-A2A,
    Evidently the –A1A, -A2A, AA, etc. on the end of the part number is a minor variant that did not change the operating specs. You should be able to ignore it and have everything work good.
  4. 1. Yes, you need both a TB and EGR spacer. They're usually sold in kits, anyway.

    2. As big as you can get it. With MAF meters, you just want something that will send a good signal to the computer, while at the same time doesn't act as any sort of restriction to airflow.
  5. Explorer TB? Hmmm..... That's an idea worth considering. Thanks for the suggestion.

    Let's say I find one and its corresponding spacer but the accessories like TPS or EGR stuff is missing. Will those things transfer from my stock TB to the Explorer TB?
  6. I have both the Explorer intake and 65mm TB that came with it. I plan on using my stock Mustang EGR spacer and port it to match 65mm.

    I know I'll need to modify the Explorer TB to fit. I'm looking up tech articles to help me in this process. If any members here know of any good tech articles or videos on the subject, please post them.

    Thanks to everyone participating in the threads I start. I appreciate your time and input.
  7. Porting the egr spacer won't work. You will cut into the water jacket.
  8. Has anyone ever flow tested the Explorer TB VS the stock 60, VS aftermarket 65mm TBs? Just curious.
  9. A guy I know that's been working on these things for many years said porting the stock spacer to match a 65mm TB is what he has done in the past with no problems. It only needs a small amount removed to match up according to him.

    I find the conflicting opinions interesting. Maybe you are correct. Or maybe you didn't realize it was just a small amount of material needing removal.

    Maybe others will chime in with their knowledge.
  10. If he can get it to match power to you. I burned through mine pretty quickly
  11. Years ago, when I first bought my old 70mm TB, I had access to a machine shop, and I plugged my EGR spacer into a CNC mill and programmed it to cut a 70mm bore in it. It COMPLETELY blew through the wall and rendered the spacer useless. 65mm? Maaaaaybe, but you're gonna have some really thin wall sections. I suppose it's worth a try, though.
  12. Anyone know the bore diameter in mm of the stock '92 EGR spacer?

    Also, will the Explorer EGR spacer work on the Mustang along with the Explorer TB and intake?
  13. Been there and done that - No. You'll need to buy an aftermarket part to get everything to fit correctly.
  14. If I go EGR delete, will I get a check engine light? If so, can I somehow prevent the check engine light with regard to the EGR system but keep it operable for the other systems?
  15. Do it right the first time and have a working EGR.

    Some basic theory to clarify how things work is in order…

    EGR System theory and testing

    The EGR shuts off at Wide Open Throttle (WOT), so it has minimal effect on performance. The addition of exhaust gas drops combustion temperature, increases gas mileage and reduces the tendency of the engine to ping. It can also reduce HC emissions by reducing fuel consumption. The primary result of EGR usage is a reduction in NOx emissions. It does this by reducing the amount of air/fuel mixture that gets burned in the combustion process. This reduces combustion temperature, and the creation of NOx gases. The reduced combustion temp reduces the tendency to ping.

    The EGR system has a vacuum source (line from the intake manifold) that goes to the EVR, computer operated electronic vacuum regulator. The EVR is located on the back of the passenger side shock strut tower. The computer uses RPM, Load. and some other factors to tell the EVR to pass vacuum to open the EGR valve. The EGR valve and the passages in the heads and intake manifold route exhaust gas to the EGR spacer (throttle body spacer). The EGR sensor tells the computer how far the EGR valve is open. Then computer adjusts the signal sent to the EVR to hold, increase or decrease the vacuum. The computer adds spark advance to compensate for the recirculated gases and the slower rate they burn at.


    There should be no vacuum at the EGR valve when at idle. If there is, the EVR (electronic vacuum regulator) mounted on the backside of the passenger side wheelwell is suspect. Check the vacuum line plumbing to make sure the previous owner didn’t cross the vacuum lines.

    Diagram courtesy of Tmoss & Stang&2birds. (the diagram says 88 GT, but the EGR part is the same for 86-93 Mustangs)

    The EGR sensor is basically a variable resistor, like the volume control on a radio. One end is 5 volt VREF power from the computer (red/orange wire). One end is computer signal ground (black/white), and the middle wire (brown/lt green) is the signal output from the EGR sensor. It is designed to always have some small voltage output from it anytime the ignition switch is the Run position. That way the computer knows the sensor & the wiring is OK. No voltage on computer pin 27 (brown/lt green wire) and the computer thinks the sensor is bad or the wire is broken and sets code 31. The voltage output can range from approximately .6-.85 volt.

    The EVR regulates vacuum to the EGR valve to maintain the correct amount of vacuum. The solenoid coil should measure 20-70 Ohms resistance. The regulator has a vacuum feed on the bottom which draws from the intake manifold. The other vacuum line is regulated vacuum going to the EGR valve. One side of the EVR electrical circuit is +12 volts anytime the ignition switch is in the run position. The other side of the electrical circuit is the ground path and is controlled by the computer. The computer switches the ground on and off to control the regulator solenoid.

    EGR test procedure courtesy of cjones

    To check the EGR valve:
    Bring the engine to normal temp.

    Connect a vacuum pump to the EGR Valve or see the EGR test jig drawing below. Connnect the test jig or to directly to manifold vacuum.

    Do not connect the EGR test jig to the EVR (Electronic Vacuum Regulator).

    Apply 5in vacuum to the valve. Using the test jig, use your finger to vary the vacuum

    If the engine stumbled or died then EGR Valve and passage(there is a passageway through the heads and intake) are good.

    If the engine did NOT stumble or die then either the EGR Valve is bad and/or the passage is blocked.

    If the engine stumbled, connect EGR test jig to the hose coming off of the EGR Valve.
    Use your finger to cap the open port on the vacuum tee.
    Snap throttle to 2500 RPM (remember snap the throttle don't hold it there).
    Did the vacuum gauge show about 2-5 in vacuum?
    If not the EVR has failed

    EGR test jig

    To test the computer and wiring to the computer, you can use a test light across the EVR wiring connectors and dump the codes. When you dump the codes, the computer does a self test that toggles every relay/actuator/solenoid on and off. When this happens, the test light will flicker. If the test light remains on the computer or the wiring is suspect.

    To check the EVR to computer wiring, disconnect the EVR connector and connect one end of the Ohmmeter to the dark green wire EVR wiring. Remove the passenger side kick panel and use a 10 MM socket to remove the computer connector from the computer. Set the Ohmmeter to high range and connect the other ohmmeter lead to ground. You should see an infinite open circuit indication or a reading greater than 1 Meg Ohm. If you see less than 200 Ohms, the dark green wire has shorted to ground somewhere.

    Late Model Restoration may still have the Ford Racing M-12071-N302 kit with the EGR valve & sensor along with the ACT & ECT sensors for $45. See;item?item_no=M12071N302 1&comp=LRS for more details
  16. I'm convinced to keep the EGR operable. The question remains, port my stock spacer (slightly) to match the Explorer 65mm TB or get an aftermarket spacer.
  17. Aftermarket 70. Don't skimp.
  18. Aftermarket gets my vote I too have not had luck boring out a stock spacer they get too thin and the castings are way inconsistent

    Sent from my XT907 using Tapatalk 2
  19. To expand on the subject;

    I talked to my friend about mildly porting the stock Mustang EGR spacer to 65mm and again he said it should be no problem. I've ported heads myself before so I'm not afraid to try this. I know its aluminum and it will cut pretty fast so I'll be gentle and gradual. I'll let you all know how it works out.

    To the next decision in the matter;

    I'll be swapping the stock intake for the Explorer intake. I now have the chance to block off the exhaust crossover in the lower intake manifold. I know these ports have a function in the operation of the EGR system. Although I plan to have all the other EGR components installed and connected (goal to avoid CEL and related issues), what effect will blocking the exhaust crossover ports have on the function of the EGR system otherwise?

    In the old school gang, the word is by blocking the exhaust under the intake you cool the intake charge and can make a few more HP. Is there a way to have best of both worlds?

    BTW, I'll be using this write up to help me modify the 65mm Explorer TB to work on the Mustang. >>