Converting 84/85 to 86/87 ECM Problem

[Ron84TType]

I hope someone can help me out here. I had put and 86/87 ECM and chip with my old calpak chip in my car. Added the MAT sensor. 87 MAF sensor is being used also. No engine light on, thats a good thing. At a dead stop the cars fine, on throttle up the car chokes up and stumbles and a few times popping from the intake also. Just on the start it does this. Once i feather the throttle thru that it runs great. Is there some wires to change that are giving a bad signal? Maybe on the MAF or TPS or Module. The car does have an 86/87 module and coilpack. I still have that little short wiring harness between the module harness and the module itself. That was for when i converted to 86/87 coilpack and module still using the 84/85 ECM. Do i need to take that out? Is that maybe feeding wrong signals to the ECM?
I hope this info helps someone out so they can help me out. Thanks for your time. If anyone needs more info i can send it out also. thanks

[Keller]

Check the articles on doing the conversions here http://www.gnttype.org/techarea/ecmsensors/ecmpage.html and see if all the parts and wiring are correct. I think there may be one or two wires that have to be moved to make it all work.

[Ron84TType]

Scott, i understand the changing of the wires for the MAT sensor. I had done that and everything that is said to change. If there is another part in that link for changing over to 86/87 ECM, i guess i cant see it in there. This is very frustrating. There has to be some other wires to change around whether its on the MAF or TPS or some other place. If i can solve this problem with the car it would run great. If i happen to switch some wires around like on the MAF or TPS just for a test could that possibly fry something in the ECM? Let me know. Dont really need that to happen.
So Scott, your from Missouri? Is it the ST. Louis area? If so, great i dont live too far off and im always working in Missouri. I have to drive over there everyday. Anyway thanks for your input and if you know anyone who has done this to their 84/85 and it worked for them, send them my way on what the secret is.

Later and Thanks.

[pfredricks]

I have made the same ECM conversion and am having the exact same symptoms you describe: tip-in stumble after startup. It's most obvious after cold start, warm starts are less of a problem, but still there.

I've gone though the ECM wiring and I don't see any other change beyond the MAT sensor addition and switching to the 86-87 MAF.

I'm also using the 86-87 calpak, I didn't think that the 84-85 calpak would work with the 86-87 software. I'm using the original 86-87 stock chip.

Do you have a knock gauge? I see some momentary knock under aggressive acceleration, more with WOT. I'm having to run my fuel pressure around 42 lbs to keep the BLMs in the 128 range under normal driving conditions. This suggests to me that I'm lacking fuel during acceleration until the ECM adjusts the fuel.

I've also got PTE's 206/206 cam, but I don't believe that's the problem here. I've got stock injectors that have been cleaned and flowed.

Do you have a scan tool like TurboLink?

[Ron84TType]

Well i dont have a scantool. Eventually i will have that down the road. The 84/85 calpak for mine is the same # as an 86/87 calpak and i was told it would work fine. Do you have that short wiring harness that goes to the module for the conversion to the 86/87 module and coil? That harness is for converting to 86/87 module and coil with still using the 84 ECM. Since now ive changed over to 86/87 ECM would i still need that short harness? I wouldnt think so but im still not sure. Like i said, the stumbling only happens when i start from a dead stop and i have to feather the pedal till i get past that point. Once past that point the car runs fine. then when i stop again i have to go thru it all over again. There has to be someone out there that knows the solution to our problem. Get back to me if you hear anything.

Thanks

[pfredricks]

"Do you have that short wiring harness that goes to the module for the conversion to the 86/87 module and coil?"

Yes.

"Since now ive changed over to 86/87 ECM would i still need that short harness?"

Yes, you still need the adapter.

"the stumbling only happens when i start from a dead stop "

It sounds like you have an off idle stumble. I only have it after startup, not from an idle.

Have you adjusted your IAC motor?

If not, check this out: http://www.gnttype.org/techarea/faq/IACreset.html

Have you adjusted your TPS?

If not, check this out: http://www.gnttype.org/techarea/maintenance/TPS.html

You don't need a scan tool to adjust your TPS if you have a multimeter. Go get one from Radio Shack, they're cheap.

Turbolink is an excellant scan tool, I highly recommend it (but I'm not so sure about the programmer who wrote it).

[Ron84TType]

At idle is no problem, its when im moving that it does it. (when i take off from a dead stop). Yes the TPS is adjusted and the IAC has been reset. Still same problem. Ill have to go over everything again to see if i missed something. maybe even disect the wires one by one to see if anything is different in the conversion from 84/85 to 86/87. Thanks for helping out. If more info, keep it coming.

Thanks

[3point8]

Let's see if I can remember what I did when I converted my 85 GN.
Basic stuff:
-The calpak that came with the car stays with the car regardless of which ECM you use.
-You need the adapter harness between the engine harness and the module regardless of which ECM you use.
-The MAT sensor is not critical to the operation of the engine just keeps the annoying orange Service engine warning light off.
-The 7148 ECM must have an 86/87 chip designed for Turbo buicks

Now for the items I can't recall exactly:
-I believe there was comment on one of the boards that a few of the adapter harnesses had a wiring error during manufacture
-I seem to recall a ground issue involved. I ran two grounds one from the ECM to the module and one from the module to the firewall. I forget which pin was missing in the ECM harness to 7148 ECM needed the ground but if you keep after me on it I'll check see if I still have my notes from that conversion job.

My car is a T top car (leaker) so I had some corrosion in the ECM sockets I had to clean up. You might want to do a closer inspection on yours if its a T top also. My car ran fine with either the 85 MAF or the 87 MAF, apparently others have experienced problems.

That's all I can think of for now.
Peter