[Gmecm] Introduction

[Dave Jones]

Hi Jared,
I swapped my daily driver from CCC to TPI a few years back, for very similar 
reasons.
Should be a fairly straightforward swap, and I'd expect it'll fire right up 
and run decent with the F-body calibration you have.
Plenty of '8746 info in the DIY PROM and DFI & ECM forums at 
www.thirdgen.org.
There is an '8746 disassembly, as well as plenty of other useful stuff, at 
www.moates.net/fileman.  Look for a file called 61.zip
I'd expect the MAP sensor on your CCC car is actually a VAC sensor -- same 
external appearance but very different output.
I vaguely recall the CCC knock sensor being different, but I can't remember 
for sure.
I modified a junkyard GM harness for mine -- the underhood stuff was a 
no-brainer; more time went into figuring out the connections between the new 
engine harness and the existing underdash wiring, but that wasn't that 
difficult either.  I'd suggest spending a little time with a continuity 
meter and verify the actual wiring -- on mine, I found a couple of wires 
worth of difference from the circuit diagrams in the GM FSM. Also, take good 
notes on any changes you make from the OEM circuits; you may need them to 
refresh your memory later on if you have to troubleshoot a problem or decide 
to do further mods later on.

HTH,
Dave Jones
'96 Impala SS
'83 Trans Am ZZ4 TPI
'89 Turbo T/A # 1291
'97 Z28
Fort Irwin, CA

----- Original Message ----- 

> I drive a 1984 Chevrolet El Camino with a 305 V-8 and GM E4ME QuadraJet 
> carburetor, and 4-speed automatic overdrive transmission.  The carburetor 
> has become very worn and while I still pass the state-mandated emissions 
> inspection, I have become very tired of adjusting the choke every time the 
> weather changes, and it runs very rich at idle, something I've never been 
> able to correct.  I am converting it to a TBI system with intake manifold 
> and throttle body from an '88-'92 Chevrolet Camaro or Pontiac Firebird.
>
> This 305 is in good shape.  It has 160K miles and shows strong, even 
> compression on all cylinders.  I hope it takes very well to EFI, and I 
> expect much better throttle response and at least noticeable economy 
> improvements.
>
> Anyway, here is a question.  The ECM I have is a 1278746 with an ANTT 
> EPROM.  I did some research online and found that this is from an '89-'90 
> Firebird with 305, TBI and 4-speed automatic transmission.  I believe this 
> is an almost ideal match for my vehicle.  The F-body cars and El Camino 
> are actually nearly the same weight, even though they look nothing alike. 
> Is this likely a good ECM chip for getting the vehicle running and have 
> decent driveability?
>
> I have read hints that the 1278746 is the "car" version of the 1227747, 
> which is common in trucks.  I admit I have not yet started scouring the 
> archives for more information about this, but I wondered what the 
> differences are.  I did notice that there are no disassemblies of the '746 
> on the FTP site, only bins.