Predetonation/computer

[mike2020]

I just replaced the spark control module and I still have the predetonation. The only thing in the world I havent had diagnosed or replaced is the main computer box. I found one from a 1990 Rivera will this work on a 1988 Reatta??

Tks. <img src="http://forums.aaca.org/images/graemlins/confused.gif" alt="" />

[padgett]

Must be something going on I do not follow but AFAIK the only way to get detonation with proper secondary wiring is:

a) knock sensor malfunction

leaking injector

c) loose crank balancer that has rotated a bit.

d) reprogrammed PROM

almost anything else will result in no spark or a late spark, not an early one.

Please recap: are you hearing ping or something that sounds like ping ?

[Guest F14CRAZY]

Have you went into diagnostic mode to check the knock retard?

[Guest TommyH]

this the 'r' word is a bit much, phil?

[Guest F14CRAZY]

My bad, KR, the politically correct term for delaying ignition timing

[Guest alex_houston]

Yes it works, but you will have to switch the prom or it will only start and die when you let off the key.

[mike2020]

Yes, my mechanic plugged in his computer and said that the computer is retarding the spark. Knock sensor was replaced, EGR replaced, oxygen sensor replaced. What is reprogramming a prom? What is a prom? Pardon my ignorance. I wanted to put a new computer in her (88 model) from a 90 Riv. I don't know if they are the same or not???

Tks. <img src="http://forums.aaca.org/images/graemlins/tongue.gif" alt="" />

[Guest F14CRAZY]

The engine computers are the same, but you need to remove the chip/prom/memcal from your Reatta computer and put it in the Rivi computer.

[TheBlackMoon]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">What is reprogramming a prom? What is a prom? Pardon my ignorance.</div></div>

PROM = Programmable Read Only Memory

EEPROM = Electronically Erasable PROM

Geek terms for the old version of what we call "Flash" memory...

Think of a PROM as a CDR; you can write to it only once (this is done at the factory).

Think of an EEPROM as a CDRW; it can be written to several times over and over again, if you have a cd (in this case, an EPROM [just drop the word "erasable" from EEPROM]) writer.

When we say "PROM" on this site, we really mean EEPROM, but it's assumed that everyone knows it's the electronically rewritable kind of memory chip.

Better? <img src="http://forums.aaca.org/images/graemlins/grin.gif" alt="" />

And yes guys, I know it's more to it than that, but I doubt he cares, LOL! <img src="http://forums.aaca.org/images/graemlins/smile.gif" alt="" />

[mike2020]

Thanks now I know what an EEPROM is. So could that be the root of my pre-detonation problems? I mean could my EEPROM need to be reprogrammed? I have done and replaced everything else except the computer, that's why I wanted to put the one out of the 90 Riv in to see if it curred the pre-det. What would happen if I used the 90 Riv EEPROM to see if it cured the problem? If I can't do that where would I go to get the EEPROM re-programmed or where does one get a new one?

Tks. <img src="http://forums.aaca.org/images/graemlins/grin.gif" alt="" /> Some people learn from other peoples mistakes; it's too darn bad the rest of us have to be the other people!

[Machiner 55]

Look at the attachment first.

Now... the PROM/Mem-Cal fits into the blue plastic slot with the double row of pins. In the photo the Mem-cal (PROM) has been removed. The information in the PROM usually doesn't get changed unless "forced" (burned), which is what F-14 had done to his to get the car to run once he installed the supercharger on his engine. You can think of the PROM as a sort of reference library where the "brain" goes to see if what it's doing is correct for the given condition.

The "brain" (silver box) can suffer damage and cause a myriad of problems. In your case, if you are wanting to change out a part, it would be the ECM (brain) not the PROM. The prom stays with the car that it came with. When you buy a new ECM, it doesn't come with a PROM (Mem-Cal). You must remove the one from the ECM that was originally in your car and put it in the new or remanufactured ECM.

So... if you haven't modified the engine in any significant way, you don't need a new PROM (Mem-Cal) unless, of course it was involved in one of the recalls regarding hard starting. (search other posts for info regarding recalls)

Here is a link regarding my problems with an ECM.

[mike2020]

Reattajohn-just to be sure, are you saying that my problem might be in the ECM not the BRAIN (or are they one in the same)? The picture (attachment) was that the brain or the ECM? Will a 90 Rivera brain work in the 88 Reatta if I swap the EEPROM? Tks.. <img src="http://forums.aaca.org/images/graemlins/cool.gif" alt="" />

[Machiner 55]

Where I come from, when people talk of replacing the "brain" they are referring to changing out the silver box.

Silver box = brain = ECM. All three are the same thing.

PROM = EPROM = EEPROM = MemCal. All of these terms mean the same thing but are different from the brain.

When you order a new brain from an auto parts source you will receive a new (or remanufactured) silver box minus the PROM. You supply the PROM for the new brain by removing the PROM from the "old" brain before turning it over to the auto parts guy. The auto parts guy wants your old brain as a "core" that will be sent back to their supplier so that they can remanufacture it. You can keep your old brain but you'll get charged another $70.00 just for the privilege of owning a defective unit. As with most electronic or electrical parts, there is usually a no refund policy in effect. You buy it you keep it unless you can prove it is defective.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body"> The picture (attachment) was that the brain or the ECM? </div></div>

The brain with the access cover and MemCal removed.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body"> Will a 90 Rivera brain work in the 88 Reatta if I swap the EEPROM? Tks.. </div></div>

It might. Try it and let us know how it turns out. I don't believe it'll hurt anything. Nothing will blow up or melt.

Anyone else have an angle on this?