ECM Deletion

[johnson350]

Well guys, today was the day the ECM came out of the car. Took about 10 minutes to unplug everything. Shoulda got more pics, will snap more tomorrow. Made sure to keep everything intact (ie, no hacking wires).

The car started running rough a little bit ago, turns out the TPS was bad, so it was dumping tremendous amounts of gas and sputtering and spitting pretty bad while accelerating. So I got to thinking, eh I'll just dump the whole setup (actually runs damn good with that electro carb and EST distributor unhooked from the computer). It would be much more reliable. And reliability is an important factor for me, as this is my DD.




Had a Dualjet laying around that came off a '79 305. Needs a rebuild.


Swapped the hot air choke setup and converted to electric.


And I still gotta fab up a plate to cover up that hole where the ECM harness goes through the firewall. Also still need a vacuum advance distributor, about 85 bucks, and a carb rebuild kit, so about 110 bucks is all this will cost me.

I do have several questions regarding the A/C. I read that the computer controls something with it, do I need to rewire something? In this car the A/C harness and computer are completely different and never cross, sooooo, not sure. It didn't work before I removed the ECM, and actually debated getting rid of it too. But after the heat today, decided to keep it and fix whenever funds allow.

Also that Smog pump attachment, what to do with it? It is super ugly, do I just get a cutoff wheel and get creative? I think a PS bracket off a Buick 350 would work, but so damn hard to find.

 

[johnson350]

Also I am wanting to keep the EGR. Just not quite sure how to route the vacuum hoses.

Im thinking running a ported vacuum switch, hooked to a ported vacuum source on the carb, then running a line off the ported vacuum switch to the EGR. Also should the distributor advance run off the ported vacuum switch too or should it just run straight to a ported vacuum source on the carburetor?

I plan on running the two on the same vacuum circuit, that should work, right?

I drew a picture, somewhat hard to explain...


OR



So I guess the main question is, should the distributor run before or after the ported vacuum switch?? Do I even need a ported vacuum switch??

 

[johnson350]

Oh yes, and of course can't forget about the lockup. Plans in the future include a low vacuum switch, but for now a manual switch. Need to run some new wires through the main engine harness down to the case plugin, since the previous lockup wires ran throught the computer harness, which is no longer in the car.

 

[DoubleV]

If you are to run ported vacuum then do it like your second pic shows otherwise you'd get no vacuum advance until the car heats up and there's no advantage to that. That being said, run manifold vacuum to your distributor for smoother idle.

 

[jacobdavis1979]

I dont think i can answer all your questions but i can answer a couple.

What the computer controlls on your A/C should be nothing. Unless it has an electrical idle up solenoid from the factory but i think that year had vacuum didnt it?

Now for your lockup in your trans theres a couple ways those came out of the factory that year i think. It may still work but most ive seen are controlled by the ECM. So what you can do is hook the lockup to a toggle switch. Now people are probly going to tell you no you cant do that youl burn up your trans. OK heres the deal dont let anyone tell you that cuz they probly dont know better you can very well hook that lockup to a toggle switch with NO Problems at all it will not hurt it just flip the switch at cruising speeds and shutoff when idle. Il tell you another secret about lockup. You dont even have to use it as long as your transcooler in the radiator is in good working condition you will be fine. But trust me you will like the toggle switch idea better.

Take it from me ive never converted CCC to non but i have converted TBI to Carb with no issues so ive been around the block a few times.

 

[johnson350]

If you are to run ported vacuum then do it like your second pic shows otherwise you'd get no vacuum advance until the car heats up and there's no advantage to that. That being said, run manifold vacuum to your distributor for smoother idle.

Right. The reason I was adding a ported vacuum switch into the equation was because I didn't want the EGR to work while the engine was still cold, may cause some sputtering.

 

[johnson350]

The carb did have one of those idle speed things on it, I think it's called an ISC.

I had a toggle switch wired in before I removed the ECM, for whatever reason the computer wouldn't lock it up. Yes, I really do like having it, keeps the engine at lower RPM's saving me a buck or two on gas. The radiator is a few months old, so I should be ok running it without lockup for a little while, just until I get around to running some wires down to the transmission.

I'm sure converting a TBI to carb setup was much more complicated than this. This is pretty straight forward, I merely just unplugged every thing, removed emissions stuff, plugged some holes, swapped carbs and distributor and that's about it.

 

[johnson350]

Got my vacuum advance distributor from Autozone today, 82.99, price matched from RockAuto. Was originally 125, so I'm happy about the 40 dollar savings. Not just waiting on the carb kit that was supposed to get here today.