Welcome to 2CarPros.
If the gauges are jumping around, that leads me to believe there could be a grounding issue. Have you checked the ground on the battery? Are both terminals clean and tight? Also, check to make sure the grounds from the battery to the engine block and body are in good condition, tight, and not corroded.
Next, take a look through this link. It explains what can cause a backfire.
https://www.2carpros.com/articles/engine-backfires-while-running
Next, I need you to check for diagnostic trouble codes. The truck has an OBD 1 system and all that is needed to check for codes is a test light. Follow the directions in this link and let me know what you find.
https://www.2carpros.com/articles/ford-lincoln-mercury-obd1-1995-and-earlier-diagnostic-trouble-code-definition-and-retrieval
https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester
Let me know what you find.
Take care,
Joe
Jul 23, 2019 at 8:07 PM
