Perplexing Problem! Runs On 1 Rotor, using Microtech LTX8s
 

(I also have this posted up on the Nopistons forum)

Ok guys, here's one for you. I've been building my brother's 79' mariah widebody first gen for the last 4 years now and I really wanna see this baby on the road for good!! The basics are: It has a streetported 13B w/ 3mm apex seals, lightened rotors, Cartech air/ liquid intercooler, 48 IDF throttle body, T04B turbo, 550cc primaries, 860cc secondaries (soon to be 1680cc), and a Microtech LTX8s ECU. Now, I need to state that it started up and idled EXCELLENT when we had the other ECU (Stinger 4424 >other Australian aftermarket ECU).
Ever since the Microtech was installed, the engine would randomly lose a rotor while running and stay that way. Recently, it starts up only on one rotor and after a minute or so, the second rotor starts firing, but starts to cut out off and on. I never had this problem with the last ECU!!!!!
So, for starters, I did a compression test...........hot and cold. both times it registered 105 105 105 for the front and 105 105 105 for the rear. Whether the engine was hot or cold, it made no difference.
Next, I figured one of the injectors was sticking or was not firing (which were originally fairly new 740cc or 760cc primaries). When a rotor would be lost, the AFR's went from 12-ish, up to 14 or 15-ish. So, naturally, this is what I figured. So
I checked all the wiring carefully..........all wires were perfectly fine. No grounding out, no wires touching each other, no "splices", "gashes" or "holes" in the wires, etc.
So, next, I figured bad injector. Just changed to a pair of clean and flow tested stock Mazda 550cc injectors yesterday. Still, the problem remains. I have checked the spark several times, I have checked the coils, I have changed the plugs, (even to a different heat range!!). I tried changing the leading coil, but it staill ran the same. I even created a "daisy chain" for the grounding system >> battery>chassis>engine block in case it was a grounding problem. Still, the problem remains. I have tried tuning it out, but it stays the same.
So, as of today, I was left with only one option left: To finally get the "specific" Bosch coils for the ECU from Microtech in Australia. They should get here within a few weeks, but I fear that the problem will still be there.
So, after all that being said, has anyone ever encountered this before? Does anyone have an answer?? I'm over my head in frustration just trying to figure it out and I've triple checked everything!!!

Brian

By the way, the car ran pretty well when we were using the other ECU before this whole Microtech installation. My brother put roughly 2500 miles on the engine before taking out the Stinger 4424 ECU and installing the Microtech LTX8s.

Well if you were using stock coils before and didn't put in resistors, you could have damaged something. That's my only guess. Sorry i couldn't be of more help

what coils do you have on it at the moment??

if you dont have 4 seperate bosch coils in it that is your problem,

Dale

Originally, I was running 2 separate MSD coils for the leading, and 2 stock 2nd gen coils for the trailing. After that, I tried using just one of the ignitor switch outputs for the leading coils (coming from the Microtech) and hooked it up to a stock 2nd gen leading coil. No difference.

I truly hope that it's the coils that are causing the problem!!! By the way, is this sometimes a problem with the LT8 (not the (LTX8s) when hooking it up to stock 2nd gen coils? I installed my friend's LT8 in his 2nd gen, and sometimes when he gets it started when the engine is cold, it will run on 1 rotor for a minute or two before the 2nd rotor starts to fire.

if you had MSD coils hooked straight to the microtech you may have burnt out the igniters as they require .5ohm coils, most msd coils are .2 ohms,

did you remove the igniters off the stock 2nd gen coils??

if you mate is having problems like that i would change spark plugs to a different heat range and type of plug

Dale

I really hope that I didn't burn out the igniters!!!!! OMG, I'd be in a world of shit then!!! The MSD coils that were used were the blaster type that are typically for the carbureted models (the cylinder shaped coils that fit in the holes where the stock coils went on the first gen rx7's). And yes, I most definitely removed the igniters before I originally installed the coils last year. Currently he is running BUR9EQ plugs all around. How can I tell if the internal igniters are still good inside the Microtech?? I really hope that is not the problem!!!

Also, I forgot to mention: Everytime we try to get the car started, it constantly backfires until it just BARELY gets running, but then it's usually on one rotor.
The first day the car was ever started with the new Microtech installation, it started right up without really any problem!! After it sat there running for like 15 minutes, it started running on one rotor completely out of nowhere!!! It had already been running for 5-10 minutes at normal operating temperature at that point!!! Ever since then, the car has never quite run right. That is when I checked everything, changed coils, plugs, injectors, etc. Nothing made a difference!!! I hope to God that I don't have to send this Microtech back to Australia for a new one!!!

Ok, I just finished installing the 4 Bosch coils, but unfortunately it's too late for me to start the car because of the neighbors. I really hope that this solves the problem because this is the absolute last answer that I have for it. I'll be sooooo pissed if it starts and runs the same way!!! Guess I'll find out tomorrow!!