EFI-ECM harness changes
Thread Starter
Burning Brakes
Joined: Sep 2008
Posts: 810
Likes: 58
From: Alva Florida
EFI-ECM harness changes
If changing a complete harness to a different EFI computer (XFI for example) in a 1990 C4 coupe, how do you get the computer to think everything is ok, so the climate control system will work properly? I've contacted EFI people but my emails are not replied to.
Hoping for some options because I want to do EFI upgrades, and this is an area I cant figure out. I've searches for days to no avail.
I changed my '90 coupe to a 421 w/ a carb, and now I want to put an aftermarket EFI on it. I have a switch to ground my a/c on it now, but am hoping I can find a way to make the factory system work correctly.
Thanks.
Hoping for some options because I want to do EFI upgrades, and this is an area I cant figure out. I've searches for days to no avail.
I changed my '90 coupe to a 421 w/ a carb, and now I want to put an aftermarket EFI on it. I have a switch to ground my a/c on it now, but am hoping I can find a way to make the factory system work correctly.
Thanks.
Burning Brakes
Joined: Nov 2008
Posts: 995
Likes: 1
From: Naples Campania
I TRIED to put the Edelbrock Pro Flo 2 system on my 91 L98. It didn't work because it was designed to convert a carb to an EFI. That might be the type of thing you are looking for. Call up Edlelbrock and see what they can do for you.
Also, if you want to send an e-mail to ANYONE about doing some crazy stuff to a chevy SB, talk to TPIS. If you see some of the s*** they have done, you might just have to get a new pair of pants.
Also, if you want to send an e-mail to ANYONE about doing some crazy stuff to a chevy SB, talk to TPIS. If you see some of the s*** they have done, you might just have to get a new pair of pants.
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
Maybe it's different in '90, but on my trusty rusty ol' '86 there is very little connection between the A/C and the ECM. The only connections are the A/C clutch signal and the A/C high pressure switch signal. The clutch signal causes the ECM to raise the RPM to compensate for the extra load of the compressor and the high pressure switch causes the ECM to turn on the fan to cool the A/C condenser.
Instructor
Joined: May 2001
Posts: 186
Likes: 0
From: Midwest
I've done a few Accel Gen 6s and 7s on pre-90s without a problem. The 90+ have the CCM providing a couple of VATS signals to the stock ECM, not sure what to expect there, possibly not a problem. Some of the more popular aftermarket EFIs tech support people can point you to organizations who make conversion adaptors, when I was a dealer for Accel, we had 3 or 4 companies that did.
Thread Starter
Burning Brakes
Joined: Sep 2008
Posts: 810
Likes: 58
From: Alva Florida
Actually, I was thinking about using the FAST EZ EFI, because I have a radical cam, and know nothing about tuning chips, and have wasted a lot of money paying people to screw up my car (that's why a carb is on it). I love the look of a carb and that system might work for what I want to do.
Now if only I could make the a/c ground through the computer like it's supposed to.......
Thanks so far though!
Now if only I could make the a/c ground through the computer like it's supposed to.......
Thanks so far though!
Race Director
Joined: Feb 1999
Posts: 12,772
Likes: 17
From: Indianapolis IN
sent you a PM, call me if you want
I left all of hte AC wires in the dash and only removed the wires going to the engine control,
the ac compressor still goes to the plug that plugs into the dash harness, and the power wire to the AC compressor is the signal wire that tells the FAST that the AC is on so it can increase the engine idle rpm
Then the AC enable wire from the FAST controls the ground by dropping the power to the relay, the relay is only used as a pass through for the AC Compressor ground, when the relay is switched off, the ground to the AC compressor is interrupted so the compressor disengages to release the load on the engine.
My oil pressure sensor goes to the plug under the dash
My AC Compressor wires go to the plug under the dash
My Oil Pressure sensor is still wired through the Fuel Pump Relay
My VSS still goes to the dash and the FAST ECU in parallel
My SES from the FAST goes to the dash so the SES light still works
The only function I "think" I will loose is the AVG Fuel MPG and maybe the MPG
You got questions, we've got answers,,,, isnt that a commercial
I left all of hte AC wires in the dash and only removed the wires going to the engine control,
the ac compressor still goes to the plug that plugs into the dash harness, and the power wire to the AC compressor is the signal wire that tells the FAST that the AC is on so it can increase the engine idle rpm
Then the AC enable wire from the FAST controls the ground by dropping the power to the relay, the relay is only used as a pass through for the AC Compressor ground, when the relay is switched off, the ground to the AC compressor is interrupted so the compressor disengages to release the load on the engine.
My oil pressure sensor goes to the plug under the dash
My AC Compressor wires go to the plug under the dash
My Oil Pressure sensor is still wired through the Fuel Pump Relay
My VSS still goes to the dash and the FAST ECU in parallel
My SES from the FAST goes to the dash so the SES light still works
The only function I "think" I will loose is the AVG Fuel MPG and maybe the MPG
You got questions, we've got answers,,,, isnt that a commercial
Last edited by LD85; Sep 14, 2011 at 07:02 PM.
