I just replaced a defective ECM in my 86.
The old one was a 1227165, I put in a 16198259. I used my old PROM, Delco # BUA 1728.
The ECM gives me only a code 12. But it will not idle, and is dumping so much fuel into the engine, that after running for 45 seconds, the garage is filled with gas smoke. I did NOT have this problem before.
The reason I replaced the ECM was because it was throwing out a bunch of false codes. Now I get no codes, but something else is wrong.
Even if nothing is wrong with the PROM, is it an OK number to use with the updated ECM? The previous advise I got here on the Forum about updating the ECM made no mention of using a different chip, and no part numbers for that were given either. So I assume I'm ok using the original. SO.....
Where else should I look for this rich running problem ? It's too much of a coincidence to not be connected with the ECM replacement.
:smash: :smash: :confused:


[Modified by DI2FLY, 7:00 PM 3/15/2002]

 

Couple things.

1) You don't have to replace the MEMCAL when you replace the ECM. As long as your Vette is still a 350 with a 700R4 and 3.07 rear end gearing, this should be an OK chip to use.

2) Since the problem is at startup, keep some of these things in mind: The O2 will not be used for fuel correction. That means if for some reason (faulty FP regulator, sticking open injectors) things are rich, it will not even try to correct until it has entered closed loop mode.

3) Timing could have changed somehow and the failed part is not setting a code.

4) Your coolant temp sensor could be reporting incorrect values. It is located at the front of the plenum above the timing chain cover and under the throttle body. There are 2 sensors there, and the CTS has the smaller of the 2 connectors. This sensor does NOT report to the dash...meaning you could have a faulty CTS but your gage shows normal.

5) Cat could be clogged (and if it wasn't, it will be if you keep running it rich at idle. I smoked mine this way ;) )

6) TPS could be misadjusted or worn out. This usually sets a code but not always.

7) By some odd chance of fate, one of your injector banks could be grounded continuously. Usually the ECM takes care of the grounding because the injectors have constant power to them and that ground is used to pulse them open. Put your finger on a couple of them to make sure you feel a little bit of a tapping or clicking. I would assume a blown fuse would result from this though :confused:

8) MAF sensor and or assorted MAF relays could have bit the dust. Tap the MAF sensor lightly with the enging running (or maybe even unplug it altogether) and not for improved/changed idle quality.



[Modified by HighHopes85, 8:29 PM 3/15/2002]

 

Thanks for the info. MAF was checked out to be OK. Both MAF relays were just replaced.
I will check the other items you mentioned.
Could the new ECM be bad even though it flashes a code 12 ?
I figured maybe some injector banks are stuck open, but I hate to run it long enough to check for that.
Any info is appreciated.
:seeya

 

I blew a driver in the ECM and my passenger side bank of injectors weren't firing. It showed a code 12, still idled because the O2 sensor was on the drivers side...

ECMs are usually put through some sort of testing before they are shipped out. In fact, every time I have blown an ECM (somewhere around 5 to date...I like lifetime warranties) I have usually found the direct source of the problem. So IOW, I have never had one just bite the dust outta thin air and have never had a refurbished bad one. But weirder things have happened to me. :eek:

 

OK
I'll look past the ECM and focus on the wiring for now. I guess I should look for a short or improper ground. This'll be an all nighter, I can see.... :mad

 

The ECM I got from GM was defective. Replaced it, now the thing runs perfect, as before, but I still have the code 33.
The only thing I haven't replaced is the MAF unit.
Where's the most reasonable source for one of those?