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Thread: Custom build 1990 Mustang stock injection need help

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  1. #1
    Carb and Points!
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    Custom build 1990 Mustang stock injection need help

    Hello all i am new to the site. I didnt know if i should of posted this in the Gm or Ford section but being the injection is from a 1990 mustang i will give this a shot.

    Ok my build. 1984 Pontiac Fiero. Motor is a 1993 Cadillac 4.9 complete from pan to intake. Fuel injection is from a 1990 Ford mustang HO 5.0/302 from throttle body (custom plate made to fit GM intake) down to a new computer system.

    Funny build huh? Well anyhow it works! But I am having a small issue that I want to get rid of. So far all the sensors are brand new and been replaced but the mass air flow. The issue are the idle. It dont like to idle the same every time. Most of the time when I come to a red light or stop sign the idle drops so low it stalls. To keep it from stalling i put it in neutral and when i take off I have to give it a small amount of gas and put into gear. It almost sounds like I put a 480 lift cam in it sometimes carrying on jumping and what not. It never blows black smoke. Also when going down the road it loses power! I know for a fact it has to do with the fuel system because that's what it feels like. It feels it don't get enough fuel some times.
    I think it might be the mass air flow but I don't want to spend $200 and that not be the problem. I have a video on youtube called Ruffy,s V8 fiero throttle body and computer for a small look.

  2. #2
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    wow, that is an odd combination of parts...

    seeing that it's run by the ford computer, this is the correct section.

    you have any way of datalogging it to see what's going on in the near-stall conditions?
    1995 Chevrolet Monte Carlo LS 3100 + 4T60E


  3. #3
    Carb and Points!
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    No I dont. I wish I had the extra money to get a tool to tell me the error's that's going on.

  4. #4
    Fuel Injected!
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    yeah ditch the EEC and grab a 7730 lmao. jk. ever tried EECtuning.org?

  5. #5
    RIP EagleMark's Avatar
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    Quote Originally Posted by Ruffy View Post
    No I dont. I wish I had the extra money to get a tool to tell me the error's that's going on.
    Most auto parts stores will do that for ya...

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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  6. #6
    Fuel Injected!
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    Some questions. What is your fuel pressure? What injectors? What EECIV manual (A9L) or auto (A9P) or something else? Is it a manual or auto tranny? Do you have a VSS wired in?
    If you are using a manual ECU with an auto tranny and no VSS you will get those stalling issues like you described. I had this issue when I switched over to an auto tranny. I switched to the auto EECIV and it worked good with no VSS. It still idles down pretty far when coming to a stop but doesn't stall. This is on a 5.0 though. How did you get the pip signal from the caddy ignition?

  7. #7
    Fuel Injected! jameslleary's Avatar
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    You can pull codes with a paper clip or jumper wire. You can also use a test light in place of the VOM. This diagram is from the Charles Probst book:
    And, may be a stupid question, but did you modify the Injector harness to acommodate the Caddy firing order? Also, make 100% sure that you have the Hegos on their correct banks? Questions from my past experiences, I started on mustangs. Also, did you pull the system from a mustang, or is it a set up that you bought from someone...there are 2 firing orders for ford 302's.

  8. #8
    Carb and Points!
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    Quote Originally Posted by cmaje72 View Post
    Some questions. What is your fuel pressure? What injectors? What EECIV manual (A9L) or auto (A9P) or something else? Is it a manual or auto tranny? Do you have a VSS wired in?
    If you are using a manual ECU with an auto tranny and no VSS you will get those stalling issues like you described. I had this issue when I switched over to an auto tranny. I switched to the auto EECIV and it worked good with no VSS. It still idles down pretty far when coming to a stop but doesn't stall. This is on a 5.0 though. How did you get the pip signal from the caddy ignition?
    Back to the VSS thinger. No mine isn't plugged in nor is the speedo plugged in. I think that VSS has 4 or 5 wires and is a round shape plug. The funny thing is not only coming at a stop does it do a low idle but also going down the highway it boggs some times like its not getting much fuel. Would the VSS wire do that also?

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