EFI Help

[broncodude_73]

I just finished installing an efi system in my 73. I went to start it up and it started but it wouldn't idle correctly. It would only idle at 2300 to 2800 rpm. I played around with the idle air bypass sensor. I even changed it for another one that I had in the shop. No change. Then I changed my throttle body. I had a modified TB on that I bored out and made a new flapper for so I thought maybe that’s the problem. I changed it back to a stock TB. This helped. Now it wants to idle, but now it idles very rough if it idles at all. I then pulled the plug on the distributor that allows me to set the timing this helped, but it still surges while trying to idle. I have not run a diagnostics test.
The other twist is that the motor it is on is a stroked 393 with a lightning lower intake Gt-40 upper 24# injectors 70 mm mass air calibrated to the injectors.
The computer is stock to 91 Gt A9L.
Is this my biggest problem?

Thanks for any help.

 

[a67and77]

Kind of sounds like a fuel problem or a bad computer. Let me think about this one ?:?

 

[KST1]

First off, you should try to pull codes. That's one of the benefits of EFI, it can tell you what's going on. Sometimes however, you'll get a no code and still have a problem.

I think you should check the Throttle Position Sensor. They can go bad and give some pretty funny running conditions. To check you pull the plug and use a multimeter to check high and low voltages corresponding with closed and open throttle. I don't have the correct voltages with me right now, but someone should be able to provide these for you.

-D

 

[casadejohnson]

I think your computer should work with the 24#ers and larger throttle body. My brother runs a 351 in his 92 Mustang and has 24# injecters and a calibrated 75mm throttle body. His is not stroked so its not exactly the same but I would think you would be OK. A while back I read that Ryan from Ford Fuel Injection was running 24's on his and it worked fine. I would look for a vacuum leak first. I had serious idle issues when I first set my EFI up and it turned out to be a leaking vacuum line. What Are you running an EGR? Its possible that you have a bad computer but thats a problem I have never experienced so its hard to say for sure. Do you have another vehicle you can swap a computer out of just to test it? When I bought my computer, the guy I bought it from sent me an older speed density " By mistake " computer instead of the A9L that I paid for. I used my mustang to test the computer and it would idle very rough. He sent me the correct one and it idled perfect. I have found that there are more than a few dishonest guys out there trying to pass off older speed density computers as Mass Air computers. Did you get your from a reliable source?