Wierd Prom Issue - HELP

[corvairnut]

I almost dont know where to start, so I will from the beginning.

I bought 6 ea 16196395 ECMs. I remove each prom, cut out the existing chip and solder in a terminal to later install allow a removable 27C512 chip.. I use the OD$ mask and all is well with 4 of the 6. Each terminal and pinout was checked and passed. The Prom work in all ECMs and all ECMs were checked with other proms/chips and later with a romulator that I use. I have also tried the prom in a 16197427 ECM, but with the same results.

THE PROBLEM: The 2 proms will run my engine, but not well, both give have strange/low readings in turnerpro and dont run well....almost like I have the wrong mask. Timing is low and skips at lower RPMs. I have verified chips and plugs my romulator into the prom and still the same problem. It appears there is something up with these proms. Both proms have knock chips with 119**** numbers printed, but I dont know if that means anything.

Any ideas will be appreaciated as I dont know where to start.

Thanks,

Ted

[EagleMark]

4 out of 6 ain't bad? Were they all V8 and are they all going in V8? I think there's cylinder select issue with mis matched memcals... not in chip, in memcal...

[corvairnut]

Unknown, but the 16196395 is a V8 only ECM if all I read is correct. I change the Cly to 6 in a custom chip for the Chev Corvair and all runs fine. Correct me if im wrong, but the mem cal will only come into play in "limp home" mode.... correct? I have always discounted the "limp home" mode anyway since I run DIS and had to set the initial timing to a 60 degree offset to make the DIS work and will not work in limp home ever since I made the change.

I bought a 7427 today and will pay attention and document as I never thought this would be an issue. this issue first came up about a year ago with another prom, and I thought it was just a bad prom..... so there ya go.

Ted

[Six_Shooter]

Spark advance during LHM will not be affected by any changes that are made to the BIN. The ignitions system will run in a base timing mode, which for most GM DIS systems seems to be 10* BTDC.

I'm not sure how the hardware side of the CYL select issue is handled with TBI calibrations. If what I suspect to be true, actually is, then in TBI modes it is in a none issue and only affects MPFI applications.

[corvairnut]

EagleMark... you may have hit something. These are V8 TBI that I changing the Chip and making a 6 Cyl Corvair Engine Chip and A couple of the ECMs may have had unknown origin. I was looking at a writeup by Bill Hamilton on Bender and he was talking about netres (network of resistors) and the V6 has a 7.5k and the V8 had 15k between pins 12&13 on end memcal chip. I have found that the ones that work have the 15K between the pins (v8) and the 7.5k (v6) are the ones Im having trouble with. If nothing else, I have found a difference that makes one work and the other dont.... and sometimes thats half the battle

Ted

[EagleMark]

He's just wonderful at claiming everything that was figured out elsewhere...
http://www.thirdgen.org/techboard/di...-starting.html

And the instructions for how to do it...
http://www.thirdgen.org/techboard/di...es-values.html