Differences in two junkyard computers - Ford Bronco Forum
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post #1 of 6 (permalink) Old 06-04-2018, 03:35 PM Thread Starter
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Differences in two junkyard computers

Awhile ago I posted about how we had tons of issues that turned out to be the computer and the aftermarket A-1 Cardone ones were pure junk, they wouldn't allow the fuel pumps to stop running, so we got one from the local junkyard and it works, and I also got a "spare" from another junkyard and that one works too but the start cold idle is very much higher, he idles high then after about 35 seconds or so goes even higher than comes back down, so we are going to put the first one back in and use this one as a backup. I asked my mechanic buddy why this would do this and he said it must be different calibration, that there is really no way to adjust the computer, it has a screw on there but you really shouldn't mess with it so we are just going to put the better of the two in. Does anyone have anything else to add to this, does this sound right?

Thank you!
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post #2 of 6 (permalink) Old 06-04-2018, 03:42 PM
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I recommend buying one on ebay with the code that matches the sticker on the door. Thats what i ended up doing and thats what workes best

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post #3 of 6 (permalink) Old 06-04-2018, 03:52 PM Thread Starter
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I did look on Ebay but at the time none they had fit. I gave the second junkyard the number that was off of the original computer and they said this would work but this is the one that revs high on cold start up.
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post #4 of 6 (permalink) Old 06-04-2018, 05:27 PM
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How high is it revving? Elevated idle is normal on many EFI systems to aid in warm up and is common even now.
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post #5 of 6 (permalink) Old 06-04-2018, 06:58 PM
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Did you see any MAP related trouble codes with the bad EEC?

Was thinking about the "high-altitude EEC", but my memory lit up, it's an emissions compliance statement.

Carbureted Broncos significant changes range from a different PCV Valve, Smog Pump BELT & Pulley, Timing Change (figuring it's retarded about 3 to 4 degrees, IDLE IS ADJUSTED, different alternator & different modulator valve if C6 equipped; new choke rod lever, different fuel/air mixture by changing metering jet.

EEC IV Broncos Overview;
"...Determining how much fuel to deliver is accomplished in two ways, Speed Density (SD) control or Mass Air Flow (MAF) control. The mass airflow sensor measures the *MASS* of the air going into the engine. By measuring the *MASS* of the air, this helps to compensates for air density changes that occur with altitude and weather changes. The air temperature sensor, the engine temperature sensor, and the Oxygen Sensors (O2 or HEGO) are also used to help determine fuel and timing requirements. Both the MAF and SD systems use barometric compensation with the exception of the 94-95 Mustangs which incorporate that function into the MAF. The SD system uses a Manifold Absolute Pressure sensor (MAP), which measures the absolute pressure (vacuum) in the intake manifold. When the ignition is first turned on, the EEC takes a quick reading of the MAP and stores that value as atmospheric barometric pressure for calculations during running..." in EEC IV Inner Workings by T Moss @ EEC IV Inner Workings

"...The Manifold Absolute Pressure (MAP) sensor operates as a piezoelectric (pressure-sensing) disc. However, rather than generating a voltage, its output is a frequency change. The sensor changes frequency relative to intake manifold vacuum. The sensor frequency increases as vacuum increases. The MAP sensor allows the PCM to determine what the engine load is. Its signal affects air/fuel ratio, ignition timing, EGR flow and altitude compensation..." by Ryan M
The powertrain control module monitors this signal to determine altitude. The PCM then adjusts the E4OD shift schedule and EPC pressure for altitude. On diesel engines, the MAP sensor measures boost pressure. The PCM monitors this signal and adjusts EPC pressure. Symptoms: Firm shift feel, late shifts at altitude.

Mass Air Flow Sensor;

by Ryan M.

Will look through my old notes tomorrow for further details.
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post #6 of 6 (permalink) Old 06-05-2018, 09:20 AM Thread Starter
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The MAP sensor was replaced months ago when we went through all of the issues back then, we put the first junkyard computer back in that was running fine and it is much smoother and better now so it was something with the second junkyard computer. I 'm going to call that junkyard today and talk to them about it, maybe they have some insight into it or might think about sending a different one as it is still under warranty.

Thanks for the replies!
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