1989 sho with 99 v8 swap. Need help

[Paul harrison]

All right guys I’ve posted on the SHO Facebook site with some help but I still need more I’ve been suggested to post on this website. I’m posting in the first GEN because the car is a first GEN Sho however I bought this car with a 1999 sho Motor.
The car was not running when I bought it however most of the work had previously been done and I believe on the previous owners information it was running at one point. I worked on the fuel system and got the car running within a few days. The car now runs however it will not ever read of above 5200 RPM. The car is running the original five speed from the 89 with an adaptor plate to the 1999 motor
After dealing with a heck of a lot of wiring left over from the swap I have narrowed down and found my range sensor wires well at least some of them in my neutral safety plug. As you’ll see from the photo it’s been quite the endeavour figuring out what the previous owner did
I have located the range sensor is well as the neutral safety switch because I am thinking that the car thinks it’s in neutral and will not wrap over 5200 in any gears. I’m looking to resolve this I’m looking to know if anybody else has done this V-8 swap with the five speed and how they tricked the computer.

Any help is greatly appreciated

 

[Paul harrison]

Sorry guys I keep saying this is a 89 force of habit my old white sho was a 89 this cars a 91. Can’t seem to edit my post. ?

 

[NoSlo]

There's several questions to be answered. Does it have the 91 transmission, or a 99? Did the swap include the 99 PCM (pretty much required for 8 cylinders) or aftermarket ignition? There's many things quite different to wire up on a different PCM, from the transmission range sensor for the shift lever (which has a resistance network on the non-digital shifter in the 99 SHO, probably different than the resistance on a 91 shifter), all the way to the ABS module input that is used on the 99 SHO instead of a vehicle speed sensor.

 

[SHO1]

The op says it has an mtx swap and I'd guess 99.9% that it's running the '99 pcm. Very well could be speed sensor/abs module related. That is in part what controlled speedo, cruise, shifting, etc,

 

[Jon Klein]

Im having the same issue with a 94 atx car that was swapped to mtx... it must be the MLPS because both have the same design. Also I can tell you that whatever it is in both cases its not the 4k rpm neutral rev limit that protects the torque converter. The rpm is well above that limit. It seems to me it is much more like the top speed fuel cut. Which in 4th gear on an atx comes on at about 5200rpm.

 

[Jon Klein]

Btw what u do to trick the computer is modify the manual shift lever position switch by taking it apart and soldering the contacts to make it think its in park and drive at the same time.

 

[Jon Klein]

Pm for instructions on how to do that.