Tell me thats not the funniest thing you ever did see. I have a 4.2L I6 in my CJ8 and I run best in limp home modes! Who said you need to program, he!! I just change my ecms out to match my driving conditions. For my morinng and afternoon comute to work I run a 4488 because it gives me a lot of PULL power and has a great top end to keep higher highway speeds. Then I use a 7746 ecm for my in town driving. It has really lean fuel mixture so I get great pedal response and can really zip in and out of traffic, lol. It does run a little hotter buttttttttttt, anyway I'll keep reading and try to get a program to stick so it'll stay out of limp home mode but til then I'll be the great limp home mode junky. GRRRRRR!!!!

 

So what does having a 4.2L in your CJ8, have to do with you running best in limp home mode?.

Or does you CJ8 run best in limp home mode?.

If your limp home mode is better then running normally, your tune has got some serious problems.

 

limp home mode has only worked well for me when I was running not enough injector. The idle was pretty rich but everything else was so good that I didn't even notice I was in limp home (eprom kicked out of ecm by stupid friend).
You need to do some serious tuning if it's running great in limp home mode but if you don't want to burn chips you can always just hook up some trim pots to tweak the fuel curve of limp home mode. RBob's done it, I haven't... yet, but I imagine it would be like Holley's old crappy pro-jection EFI controller. The one with a few pots sticking out of the side to adjust the "curves" .

 

HHHhhhmmm, aren't you the same person that was chucking in any ECM that had the same plugs as the original one. I can't believe that you haven't fried a bunch of electronics yet.
I think you need to do some more reading/searching about how ECMs work. Might want to get some connector savers. They are used in situations where connectors are dis-connected a lot.

 

Just saying what I had that it was running Grumpy thats all, and yes I have some tuning issues to deal with too. But am well on my way as of 2 hours ago I put a good bin together and it stuck, that is without going back into limp home mode. So we'll see tomorrow on the maiden voyage to work to see how much more I will like to put into it.

Yes junkcltr it was me "chucking" in several ecms to see what would happen. But then I am in the research stages for myself and have to see what works. I dont like to just have someone tell me to get this "ecm" or any other part because that is the "ONLY" one that will work. From what I read no one here could tell if one was more different from another (ecms that is), plus tonight I even put the new good chip in 6 yes 6 different ecms from 4 cyl to the v8's and road around in with each to see if there was much if any difference's. See I have 15 or better ecm's, UV chips for 20, a bag full of limp home chips (my favorites)and so on and so on. oops got three or four sets of connectors too along with 4 or five sets of injectors just to round things out. I get it from the local u-pullit joint for pennies on the dollar. I do understand that most here have had there ecm's and stuff come stock in the rides that they tweak but on mine I didnt and I built it from the wiring up and yes I still have learning to do about what works better or not even work at all but I will tell you that there is a load of ecms that can be used in any applications.

Man , I hope you didnt read the post that I'm running fuel only too, LOL

 

Experimenting as you are doing is good. That is one of the best ways to learn. Just be careful with what ECMs you use. Some of the power, grounds, and I/Os are different. It is best to look at the wiring diagram for the vehicle they came from first. Since you did your own wiring then you probably already know that.
You will get strange results using a V8 or 4cyl when installed in a 6cyl application because the hardware sets up timers differently.

 

So I guess GM just wasted $$$ coming up with custom computers for each of their vehicles .
What you're doing, or seemingly doing, isn't very good for your engine. Saying; It "feels better", and, it feels worse sounds an aweful lot like your only tuning tool is your butt(dyno). What also scares me is that you don't mention checking the spark plugs let alone using a scan tool . So much for DIY PROM board. This thread should be moved to DFI and ECM since all you're doing is swapping in different netres chips into various ecms ignoring much of the tech that has been provided here.
Good luck with the swapping, it might be a waste of your time. Just get the correct chip with an easy to use ecm like the 7747/8747/8746 and get to burning new calibrations.
If you've got information regarding the netres as in; xxxxxx part came from a v6 application and xxxxxx netres (aka calpack) came from a v8 van, etc that would be MOST helpful . Again, good luck but remember that when working with c3's, the code is different in each so swapping the eproms (bigger chips) between ecm's will only put you in limp home mode. This is because the code is looking in certain area's of the eprom for code and if the locations and code are all different then it's just not going to understand a damn thing coming from the eprom!

 

Yes JPrevost, you are right I should have put more info on the ecm numbers and cal paks and no I'm not saying that GM wasted big $$$ on the custom computers. My apologies if it got under your skin.
I have learned that through the years that even that the part numbers change the main product is still the same. So far what I have seen was what was programmed on the eprom chip and cal pak. (still no good info on soldered in rom between ecms)
As far as my engine goes I own a jeep so I always keep a back up as not to leave me strandad or roast an engine, I keep a 7747 with a chip I purchased from howell with their program on it(junk if you want to know) and a 1637 cal pak from a 4.3L chevy in it. (my bad for not saying) No I have not checked my plugs either (need to look into that) but I do keep an eye on oil pressure , water temps, tach to keep up with that for now. So as far as my butt being my dyno , you got me on that one because I do not have enough experience yet to sit at my computer desk and look at my program and tell you how it will run under certrain conditions/load/accell on the road or how much the block learn will do to get it back to 128 or the 14.7 ve that will come in time.
Now where you mentioned I am ignoring the tech here, I AM NOT! I just cant find certain things , maybe I'm doing a search wrong or not explaining it correctly. Like for example what ecm's/eprom/cal paks will interchange?Will a 7747/eprom and 4488/eprom or a 7746/eprom swap between each other for a 4.3L chevy eng from 85-91? I cant seem to find that info see I never had a stock ecm like most here, and what would happen if I put a $AO/4488 program chip in a $42/7747 ecm,will it run?(I know now because I did it) What one reads and what happens in your instance always seems to be different. I do the research myself and lots of it, but I guess I'm looking/asking wrong and also that most of you have a prgram/ecm for your type vehicle that came stock I dont so that is also why I take a chip and swap it into other ecms, now if its right or wrong that is still to be determined?
Now with that being said I do have a method to my madness. I was narrow minded at first and only looked for the holy 7747 ecm/eprom from a 88 monte carlo because that it what everyone "told" me and that is what seems to be everyones web based right up ecm of choice and at the same time I passed over 100's of useful ones ,ecms/eprom chips/cal paks and so forth. After some research and a few phone calls to howell did I find out that I could change out their eprom/cal paks to ther ecms. So I went on the hunt and got several, most of my ecms come from 4.3L cars, trucks and Vans ranging from 1984 to 1991 and have several different Id numbers on them but are all from 4.3L's. Then when I looked and asked about what would happen with a 4 cyl. eprom/ecm/eprom chips from the same years no one could tell me so I nabbed some of those and the same goes for the V8's.
Last ,I guess I will have to start keeping a log to post on what prom id I used in what ecm and what the cal pak was to keep all informed what worked for me. My apologies to all who I have confused/ticked off and thanks for all the GREAT info I have gotten already.
For the record too, this morning I'm as excited as a school girl because I got my pp2 from xtronics wednesday and put MY first doctored $AO bin to a 7232a chip in the original 4488 ecm with a 1637 cal pak and did not get the dreaded limp home light(or go into limp mode) and it ran GREAT. I do want to play with the BPW a touch but would like to get or make an aldl cable first to run lap top to datalog.

 

Yeah, some of your posts seemed a little strange at first. The beginning stages of learning DIY PROM are the most difficult. You are extremely lucky in the sense that you aren't scared to experiment. That tends to hold a lot of people back.
Good to hear that you got the equip. to start doing your own programming. Over time, you will find that with the programming tool and some knowledge will allow you to run one ECM with one MEMCAL / CHIP all the time will excellent drivability in all situations. Oh yeah, don't run V8 or 4cyl chips in your 6 cyl. There is hardware in the netres that controls timers for the amount of cyls it was intended for. Now someone told you why not to do it.
Get an ALDL cable on that thing as soon as possilbe. If you are only doing data logging (no LT1 re-flashing) then I would go with the quickie Radio-Shack ckt. If doing LT1 or using various laptop PCs then go with the RS-232 based cable. You will quickly find that you need one to see how your PROM changes affects things........even though you may not understand why it does. It all comes around in time.

 

Thanks junkltr for the help and constructive criticism and yes I know I'm gonna take some lumps along the way but how else does one learn, lol.

I did also just barrow a aldl cable from the bud who let me use his 27sf512 programmer and no he doesnt program at all right now thats why I got it.(I'm using the UV for now) I was on my way to do just that tonight and see how data log operation goes but ran into a glitch on my first eprom burn. I seem to have a prom Id conflict or what seems to be anyway. It wont let me use my scanner on it unless I change the prom ID to what I guess is the original one but when I leave the other one / one I did on it every thing runs great just cant scna it. hmmmmmmmm????

If you got some info on this or seen it shoot it my and thanks in advance for the info and thanks again for the other info goodies too.