Negative fuel trims and running extremely rich


hello Scotty! I'm a huge fan of your YouTube channel as I do all my auto related work myself. my truck has been running extremely rich (.84-1.24 volts on both precat and post cat sensor). it's a 97 Dodge Dakota 3.9l engine 2wd automatic with 138,000 miles. I have changed everything that could cause it to run Rich from Purge canister solenoid, fuel injectors, spark plugs, distributor cap and wires, ignition coil, fuel pressure regulator and pump, pulled off a bad catalytic converter and new one is already damaged from the fuel ratio. changed the IAC, TPS, MAP sensors and oxygen sensors. the only thing I haven't changed is the ECM computer but I have reset it since changing new parts. I'm literally at my wits end with this truck. the problem started about a year ago and has progressively got worse, causing stalls from the engine at highway speeds. the fuel trims are in the -30s now and will not come back up close to zero except at about 1800 rpm. It throws no codes whatsoever and has been a nightmare to try and diagnose the problem. I'm reaching out in hopes that with your knowledge and expertise you might be able to shed some light on what my cause this or how to better diagnose it. thank you for all of your amazing videos and all the help you have already done for me. I hope you're doing well during this strange time in the world and that you have a great night.

thanks for any help you might be able to share

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Scotty Kilmer
Scotty Kilmer


could be the ecm, but you should pay a guy like me to analyze it first with his dealer level scan tool to make sure it's not something else. I would guess ecm though, cause running that bad, it has to trip a code for trim being that far off unless computer or wiring to computer has failed. Anything over 25 percent has to trip codes unless computer is bad