ncgirl05 Posted June 14, 2006 Share Posted June 14, 2006 Hello!I noticed that the last 2 times I've taken my '89 Reatta out that there was quite a bit of "stumbling" until I reached the higher (60+) speeds. I did a seach on this forum and found that another fellow had experienced the same problem. His solution was to get a new ECM and that had solved everything. Since we have an '88 parts car, we took the ECM out of that and put it in my car. Lo and behold, the stumbling did indeed stop; however, my speedometer now read 124 MPH - apparently an extra "1" got thrown into the mix and the speedo does not go above 124 (or mine just got stuck there - I do not know from experience what the high number is! <img src="http://forums.aaca.org/images/graemlins/ooo.gif" alt="" />)Anyhow - are the '88 and '89 ECM's not interchangeable? Any idea why the speedo messed up with the second ECM? We switched them back out the speedo problem was solved but the car started stumbling all over again..... (sidenote: the speedo was fine in the '88 before we turned it into a parts car)Any help/advice would be most appreciated. It bums me out that I have a perfectly good ECM I could use.... except for that whole 124MPH thing.....Thanks! Link to comment Share on other sites More sharing options...
Guest F14CRAZY Posted June 14, 2006 Share Posted June 14, 2006 Yes, but you made one crucial mistake <img src="http://forums.aaca.org/images/graemlins/laugh.gif" alt="" />You need to switch the memcal/PROM/chip from your old ECM to the new ECM. There should be a cover with either torx or hex screws. The memcal is inside. All will be better after switching them. Link to comment Share on other sites More sharing options...
manikmekanik Posted June 14, 2006 Share Posted June 14, 2006 Philip is right!!The ECM IS the same, the only difference being the Mem-Cal eprom (chip) which contains the data specific to your Reatta. Checksum will fail if the chip is not matched to your cars' eprom I.D.Use only the levers (handles) provided to remove/install the chip, or damage may result, no prying allowed. Link to comment Share on other sites More sharing options...
Guest EDBSO Posted June 14, 2006 Share Posted June 14, 2006 <span style="font-style: italic">Could it be you were really doing 124?</span> or were you still in the driveway:D Link to comment Share on other sites More sharing options...
ncgirl05 Posted June 14, 2006 Author Share Posted June 14, 2006 LOL!!! No chance of really doing 124 - I was in a 35 MPH zone most of the time, and although I have a bit of a lead foot, I was (I think!) driving the proper speed!Thanks for the responses guys - I thought we had switched all the outside bits and pieces when making the change - but maybe this isn't what you're talking about? I don't recall anything looking like a chip, but I do remember one black cornerpiece held on by a screw..... so now I'm just a little confused. ACK! <img src="http://forums.aaca.org/images/graemlins/confused.gif" alt="" /> Link to comment Share on other sites More sharing options...
Roadster90 Posted June 14, 2006 Share Posted June 14, 2006 Leigh Anne,There is an outside plate (probably in the area of 4 X 5 inches) on one long edge/side of the ecm that is held on to the main ecm case by two 5 or 6 mm (the real small bolts) headed machine bolts. Once you remove that plate you will see the inards of the ecm, and there is an approx 3 inch "memory stick' right in the middle of that opening that is held in place by two lever fastening devices as Manikmechanic explains above....this is what you have to switch.When re installing the "memory stick / chip / mem cal" just gently put in place (there are little indent and stick tabs that have to align) and apply a little downward pressure on both ends of the stick itself with your fingers, and the lever fastening devices will automatically install the stick for you. You might want to just make sure that they are tight or "levered all of the way" closed though (pushing inboard lightly with your fingers) <img src="http://forums.aaca.org/images/graemlins/smile.gif" alt="" />.Nic Link to comment Share on other sites More sharing options...
ncgirl05 Posted June 14, 2006 Author Share Posted June 14, 2006 Many thanks Nic!!! We'll have a go at it and I'll report back later! <img src="http://forums.aaca.org/images/graemlins/laugh.gif" alt="" /> Link to comment Share on other sites More sharing options...
ncgirl05 Posted June 15, 2006 Author Share Posted June 15, 2006 Well, we changed out the ECM and the chip and my speedometer problem is no longer! However, I noticed that during my test drive that there was noticeable stumbling at exactly 39-40 MPH....no more, no less... <sigh> <img src="http://forums.aaca.org/images/graemlins/frown.gif" alt="" /> ... Any ideas? Link to comment Share on other sites More sharing options...
Roadster90 Posted June 15, 2006 Share Posted June 15, 2006 Recheck your gang plug connections to the ecm. Remove and refitIt is definitely a possible ecm problem symptom though..... <img src="http://forums.aaca.org/images/graemlins/frown.gif" alt="" /> sorry.....Leigh Anne,If that doesn't work, go to your local Advance or whatever parts store you have in your area and purchase a reman ecm and try it. You do not have to do a complete R & R. Just remove yours and hook up the new/rebuilt one and test the car with it hanging or laying on the floor. Most of these parts places will let you bring it back if not the problem if you explain the situation to the parts manager....good luck,Nic Link to comment Share on other sites More sharing options...
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