mustangdad68

My son and I have been fixing up a 2000 Mustang GT Convertible for several years. We originally started out with a 1998 Mustang GT coupe. But the body was not worth repairing. We found a 2000 Mustang GT Convertible body that was in excellent shape. I did some research and discovered the '98 4.6L engine was compatible with the 2000 body. So we removed the '98 engine and rebuilt it. It has your typical performance upgrades such as a performance intake manifold, K&N air filter system and the replacement of the A/C pump with a dummy pulley. Nothing fancy. We put it in the 2000 body. But it didn't run with the 2000 ECU. So we experimented with replacing the 2000 ECU with the 1998 ECU. It ran! But the speedometer and ABS didn't work. It also ran very rich. You can smell gas quite strongly from the exhaust. I have been everywhere on the internet and mechanic shops looking for answers as to how to get the speedometer working and get it running leaner. Does anyone out there have any experience with this sort of Frankenstein experiment? Do we just need to flash the ECU? I am up for anything at this point. It's a great car. It's really fast and fun to drive! Thanks for your help in advance.

dawson1112

depending on what transmission your using. The 98 is a gear driven speed sensor, while the 99+ use a magnetic pickup. It may also cause issues when slowing down or while coasting. As for it running rich, I suggest having the codes read, it may need new 02 sensors, or you may have a leaky exhaust.

mustangdad68

Thank you. I am using the '98 transmission. I have the '00 transmission also. Can I put the '00 on the '98 engine? That would be a fairly easy fix. The exhaust is leaky. A new exhaust is on our list of things to replace this coming spring. That would be awesome if that fixed the running rich issue. The O2's are all new.

dawson1112

You will most likely have to swap out the 98 harness as well, the wiring schematics show different pin out locations for various sensors and stuff. Id say that is your biggest problem is using the 98 computer on the 2000 harness.