Engine Question About Maf And Iac Valve

Discussion in 'Fox 5.0 Mustang Tech' started by Disgruntled3lf, Dec 9, 2013.

  1. So my car has had some issues since I got it. After sitting for a few hours I have to give it gas for a few minutes to keep it running otherwise the RPM's will drop <700 and it will die. I took it into the shop and the mechanic replaced the Idle Air Control valve with a stock one. This didn't fix the problem and I think it may be the Mass Airflow Sensor. It has a stock sensor but is running 30lb injectors and a V1 Supercharger. I called the mechanic and he told me it would need a different IAC because of the charger but that sounds like BS to me. He was recommended by my dad but I am not impressed. Anyway, I can see the sensor and it would be easy to replace I just need to know which MAF sensor I need to get. And also will I need a different IAC valve because of the SC?
  2. We need more info here.

    30# injectors
    Stock MAF.

    So right away, you need a different mAF, but need to know what else is done with the car. Is there a chip or custom tune to account for the 30# injectors? If not, you are probably running pig rich at idle.

    Have you run the engine codes, and what do you get?

    Any more info on the combo? Who put it together and was a custom tune done on the final setup? Other mods?

    I highly doubt the IAC is the issue. Sounds like it might be a parts mismatch somewhere
  3. I bought the car not too long ago. I have no idea if there is a tune or chip. How can I find out?
    Tried to run engine codes but the light never flashed. Instead the RPM meter went up and down like you would expect the CEL to.
  4. To run the codes, look in the tech section. Jrichker has a great writeup.

    Take some pictures under the hood area and post them. Do you have a FMU? If so, most likely no chip or tune.

    I agree it sounds like mismatched parts. Your MAF should normally match the injector size unless you have a tune or a chip to tell the computer to compensate for the difference. If not, what happens is your stock MAF is calibrated by the stock EEC for 19lb injectors, and you have 30lb injectors.. Your A/F ratio as mentioned is going to be stupid rich. Do you see smoke blackish smoke from the tailpipes or are your plugs fouled?

    You need to tell us more about the setup though in order to get you some specifics. Find another mechanic in the interim Where are you located, perhaps some other guys here can point you in the right direction.
  5. It has a check engine light. 93 lx hatchback. I'm in Cookeville, TN. There is a sticker on the back for East tn mustangs but Google is silent on them. I can post pics tomorrow. It has a ton of mods.
  6. Pull your passenger kick panel off. Look for the computer and look at the end opposite the harness connector. There is a piece of tape that would cover a plug in port. Is there a chip plugged into the computer here?
  7. Computer

    Attached Files:

  8. And what is this on the pins?

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  9. Possibly dielectric grease.

    Looks like there was a chip installed at one point, possibly a custom tune. It's been removed however. Can only speculate why.

    Are you sure the MAF is bone stock? Is there an FMU installed in the engine bay? It will look like a round disk.
  10. Has these numbers on it.
    F1zf 12b579 aa afh55 03b


    My Google fu says that's stock.
  11. Affirmative for fmu

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  12. More pics

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  13. This thing is unplugged.

    Attached Files:

  14. Still no maf pic, is it still stock?? ....what size is it??
  15. I didn't take a pic of the MAF because the numbers tell me it's stock and 55mm. I know it's wrong. But I don't know what I need to do about it. I put up a picture of the injector. It looks red to me and that would mean it's a 30lbs. I put up a picture of the computer and the FMU. I'm unclear how the computer/FMU combination works with bigger injectors.
  16. Here's some info on the FMU


    I'm going to assume everything is properly set up in terms of fuel management and such for the moment. That would lead me back to #1...running the check engine codes.

    You said the light never came on. When you turn the key to ON, does the CEL light up until you start the car? If it does, that confirms the bulb works. With the engine off, if you ground the test plug correctly, you should hear a series of clicks from various solenoids before the light starts to blink.

    Right now, i'd focus on running the codes as a priority to get a baseline as to what the car doesn't like. If you need to purchase the $25 scanner i recommended, please do as it's a very important and useful tool to have.
  17. I have the scanner ordered and it should be here in a couple days. The light turns on (and is on) but I don't remember hearing any clicks. The ground test just isn't working for me. I used this guide:
  18. Are those stock headers?!! I'm with the others, no chip and stock MAF is a likely culprit. You may want to check the fmu for proper calibration as well (though it won't effect the idle).
    Grabbin' Asphalt likes this.
  19. Yup, No chip & stock maf is no good. You need to match the maf with those injectors then look into fine tuning with your fmu/chip tune for best results.