View Full Version : ECM question
09-19-2007, 12:31 PM
I have recently rebuilt the 2.3 in our 86 ranger parts truck, and we had the cam switched with one a couple steps up from stock. I have finally worked out most of the bugs in it but still have one question.
What I would like to know is how much of a cam can the stock computer settings compensate for? I can't find the spec card for the cam, but I know it's not too wild. I think the computer is having a hard time compensating for it. It runs good but I think it could be a little better ( it seems to stumble at idle sometimes, and also after hard use like on the highway).
Any information anyone has about possible reprograming what the computer can handle would be greatly appreciated.
09-19-2007, 10:17 PM
i dont know much about that old of 2.3, what type of system does the computer run? MAP or MAS?
if its MAS, the computer will adjust itself to the increased pumping of the engine, and the roughness might just be caused by your cam profile.
if its MAP (like im suspecting), then the computer has no way to compensate for changes in the engines pumping efficiency. you'll have to get a chip custom made for your application (so you'll need to know your cam profile).
09-20-2007, 12:48 PM
Thanks for the tip. I'm just wondering can I get just a custom made chip for the ECM or will the entire ECM need to come out and be reprogramed. I know on old chevys you could get a new PROM chip for it, but I'm not sure about older Fords.
Any extra in info would be great
09-22-2007, 09:30 AM
An '86 would be a speed density system, not MAP. A 'MAP' is a sensor.
Unfortunately, Ford has always been very stingy with their computer codes. As far as I know there is no reasonably cheap or effective way to get your computer to "understand" or make good use of a significantly larger than stock cam.
What cam did you install?
09-25-2007, 05:34 PM
Correct, There are MAP sensors (manifold absolute pressure)used with speed density computers and BAP sensors (barometric absolute pressure) used with Mass-air computers. I went through the conversion on my '90 Lincoln Mark VII as they never had Mass-air like the 5.0 Mustangs did after 1989 (1988 in Cali). I had to do this as I put a stroked 5.0 into my Mark.
So to answer your question; you would need to get a chip burned for your truck. Although, a trick that sometimes works on speed density Mustangs that have had modifications is to drill a small hole in the throttle plate, start at 3/16" and drive it around. If that helps, go up to 1/4". You can go to large too, so not much more than 5/16".
09-25-2007, 07:54 PM
So to answer your question; you would need to get a chip burned for your truck.
Trouble is while there are maybe several hundred guys with Mustangs looking for chips, there are maybe 20-30 Rangers guys. And since there is very little in common, computer code wise, between these computers and a Mustang 5.0 computer, finding someone to do the coding for the new chip is next to impossible.
Although, a trick that sometimes works on speed density Mustangs that have had modifications is to drill a small hole in the throttle plate, start at 3/16" and drive it around. If that helps, go up to 1/4". You can go to large too, so not much more than 5/16".
I'm curious how that would fool a speed density computer. It just reads engine RPM and load, calcualtes air flow and then injects fuel accordingly. I could see that modification reducing the cycle time on the IAC but can't see how it would effect the A/F ratio.
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