Hi, first time post. I have a 91, F250 with 4.9L I6, 121K miles. I'm having an issue with loss of power and surging under load. There's a check engine light on but every attempt I've made to retrieve the codes is coming up - no codes. Ive tried jumpering the STI to ground and using an Inova code reader, both without any success. Any ideas how to troubleshoot this to pull the codes? Thanks.

 

No codes is a bad sign. I would pull the computer out, open it up, and look for leaking capactiors.