Chip vs. Computer Replacement??

[ShiftTheDrift]

On our 1994 Cobra, it has the J4J1 computer installed with a JMS custom chip. My mechanic and I have determined the computer is bad, not the chip.

I've been looking all over for a J4J1 replacement to no avail. My buddy Roy mentioned yesterday that there's a replacement computer for the J4J1 computer instead of a chip piggybacking on the service port.

Is this true? If so, what are the pros and cons of a chip verses an aftermarket computer?

 

[Joes95GT]

I know very little about computers and the car's electrical system, but I'll give it a shot.

I believe Pro-M makes a computer that is supposed to help out the 94-95 guys by acting as an A9L (Fox body computer).

How do you know the computer is bad? That seems very weird, and is virtually unheard of. What purpose would the bypass chip do if the computer is smoked? That seems like it's just a band-aid?

If I didn't help, this post will at least serve as a bump.

Joe

 

[rockin_rick]

I'd bet that you could run a T4MO with that same chip and it would run the chip's program just the same as it would run on the J4J1. I think that the only difference between the 2 EEC's is what program is burnt on the ROM in the EEC. The chip just causes the computer to ignore it's ROM and read the (EP)ROM on the chip instead.

The downside is the the car probably won't run (or not well) without a functioning chip.

This is just my educated guess, as I am not certain that this would work.

FWIW - ECM's are frequently replaced when they are not actually bad. It's something like 9 out of 10 replaced aren't actually defective. Are you sure it's bad?

Rick

 

[ShiftTheDrift]

Hey Joe, how'ya doing these days?

Okay guys..

We had a dead cylinder a couple days ago and in all our testing we got down to the injectors and found "before" preignition, injectors 4 and 6 were on for some reason and maintaining 10v at all times. The rest of the injectors were seen with 3v but not always on such as 4 and 6.

If you look at the ECU wiring diagram, it's the only thing between the injectors and the ECU itself that is or could influence voltage.. that is unless we're clearly mistaken; this is very possible.

The ECU has had a JMS custom chip installed for roughly 4 weeks and when doing testing, we removed the chip and reinstalled the J4J1 by itself and the problem was still present (ruling out the chip theory).

As best as we figure, the ECU must be the culprit. What do you guys think?

 

[ShiftTheDrift]

:OT: Topic is moving to a new thread.

http://members.pro3i.com/forums/showthread.php?t=482724