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89 IROC TPI 5.0F ECM/PROM ????

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Old 07-18-2014, 11:56 AM
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Car: 1986 Monte Carlo SS Aerocoupe
Engine: L69 305 H.O.
Transmission: 200-4R
Axle/Gears: 3.73
89 IROC TPI 5.0F ECM/PROM ????

Hi guys, been a while since posting but im still piddling with the old heap and making progress. I am mechanically inclined by nature i think, however this electrical stuff is like chineese to me.
This car is a 89 IROC, has the 5.0 F TPI engine, Manual trans, 3.08 rear..

My delima is refering to the ECM and or PROM. I was putting the interior back together and the ECM had been replaced at one point in its life before i took possession. I also noticed the original prom wasnt inside.
All i saw was a board that said www.moates.net on it. The thing had been throwing 3 of 4 different codes but never the same 2 codes twice other than code 14. I have fixed the code 14 since however.
Anyhow I decided to put another ecm and prom in it because i just want the car to run stock. Dont need to soup it up, its just a play toy pretty much and something to occupy my spare time.
The ECM was available from GM still, the PROM not. I couldnt see the prom at first so i didnt know what i had. I contacted the guys at moates.net Turns out the original PROM was in the old ecm just it was attatched to their board and you couldnt see it unless you pulled it all out.
So i took the orignal PROM and put it in the new ECM and the car would spin over all day but never fire. It would fire off ether however. Appears no injector signal to me.
So I took the moates ecm board and same prom just like was in old ecm and installed in the new ecm, hit the key and the car fires right up.

Im thinking with the original prom only and no moates board it may be a VATS issue. But i always thought VATS killed the starter.
The other issue is someone at one time has changed the ignition cylinder, from the factory VATS pellet key to a standard cylinder and key.

Any electrical wizards know what direction to point me in?
Old 07-19-2014, 08:40 AM
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Re: 89 IROC TPI 5.0F ECM/PROM ????

They likely bypassed the starter relay and then disabled VATs in the modified PROM. With a stock PROM the ECM won't fire the injectors.

RBob.
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