Hey guys,

I was trying to diagnose my car which has all the sudden started running really poorly, stumbling, bucking, hard start. However I was having trouble getting TTS Datamaster and WinALDL to communicate with the ECM. Never had this problem before.

The car is a '87 350 TPI

The ecm has an aftermarket prom mounted with a Moates G1 adapter. The stock memcal, I think thats the right word, was also attached to the moates adapter. From what I understand, the stock unit only provides 'limp home' functionality with my configuration. So I removed the stock memcal from the G1 adapter and started the car, testing to see if the car was in 'limp home' mode. To my suprise, Datamaster now works. It is datalogging. So for some reason the stock memcal was preventing the car from transmitting data. Interestingly the car also ran MUCH MUCH better with the memcal removed. Some I'm guessing the memcal was causing my datalogging and bucking/stumbling/starting problems.

Any ideas? Bad memcal, forcing the car into 'limp home'?

The datalog looked ok for a normally running car.

Also, with the memcal unplugged, I'm getting a code 41. No codes otherwise. I assume code 41 is due to the limp home not being there.

Are there any problems with not having the stock memcal in place, besides not having limp home?

Thanks,

John

 

Anybody? I'm willing to entertain wild guesses.

 

it probably had nothing to do with the stock memcal. More than likely, you reseated the moates adapter, and fixed an intermittent connection that was causing the car not to run right, and your scan programs to not connect. I'd bet if you plugged the stock memcal back in, it would run the same. if you had the car running and wiggled the g1 adapter or prom, you'd find it would stumble.

 

Hey

Thanks for the idea. Unfortunately, I've tried this a bunch of times and the same thing happens every time. I have even run the car on just the stock memcal without the G1 adapter, and it runs like a turd. Then I ran the car on the G1 adapter+stock memcal, it ran the same as just the stock memcal, bad. Then I ran the car on just the G1 adapter and it ran much better. So what does this mean?

I've rerun this test a few times and the results are repeatable.

 

thats a very strange problem then. You have a prom in the G1 adapter, so the car is running off of that.

the only thing you are using with the stock memcal in that case is the netres, which should effect the limp home stuff, as well as the cylinder select. I suppose if something is shorted there, and changing the cylinder select, it would cause those symptoms. I would also guess that would cause the same problem, regardless of which prom is running (stock, or the one in the G1), that would explain why it is only effected when the stock memcal is plugged in. I don't know for sure, but I thought the ecm should default to 4 cyl mode with no resistor for the cyl select, so thats weird.

can you try another stock memcal just to test? if it seems to run OK and scan without the memcal, i suppose you could run it like that, you just won't have the limp home backup. it's probably best to try and test another one, and keep it, if you can.

 

Yeah I basically came to the same conclusion. Somehow the stock memcal got messed up. Seems really unlikely, but I have no other explanation. Looks like I will have to buy a new memcal, looks like these things aren't cheap.

Thanks for the thoughts.

John