Hotrod Johnny
New Member
After searching the forums without success for a similar issue, I'm posting with with the hopes for advice and suggestions from the community.
My 2013, 5.4, 120k miles, recently started to accelerate much slower when applying any more than light throttle. When driving on surface streets or while cruising at highway speeds with light throttle, all seems well, but with an increase in load (hills) or when accelerating up to highway speeds, there is a very noticeable reduction in acceleration. No CEL or codes from an OBD scanner. I changed the plugs, but no improvement. A recorded data log with my OBD scanner did show an unexpected lack of ignition timing advance when throttle position was more than 30% and rpms exceeded 1600. I'm not sure what is normal for these values, but I would expect to see more than 0.0, -2.5, 3.0, 1.5 degrees of advance as the engine accelerated up to 3,500 rpm. Once up to speed and throttle position returns to 15%, ignition timing is in the mid to high 40 degrees of advance. Is the computer pulling timing for some reason? This has been going on through multiple tanks of regular unleaded from different sources. I would be glad to share more from the data log (short term and long term fuel trim, MAF, O2...etc) not sure what is normal for these readings. Desperately appreciate any suggestions for further troubleshooting.
My 2013, 5.4, 120k miles, recently started to accelerate much slower when applying any more than light throttle. When driving on surface streets or while cruising at highway speeds with light throttle, all seems well, but with an increase in load (hills) or when accelerating up to highway speeds, there is a very noticeable reduction in acceleration. No CEL or codes from an OBD scanner. I changed the plugs, but no improvement. A recorded data log with my OBD scanner did show an unexpected lack of ignition timing advance when throttle position was more than 30% and rpms exceeded 1600. I'm not sure what is normal for these values, but I would expect to see more than 0.0, -2.5, 3.0, 1.5 degrees of advance as the engine accelerated up to 3,500 rpm. Once up to speed and throttle position returns to 15%, ignition timing is in the mid to high 40 degrees of advance. Is the computer pulling timing for some reason? This has been going on through multiple tanks of regular unleaded from different sources. I would be glad to share more from the data log (short term and long term fuel trim, MAF, O2...etc) not sure what is normal for these readings. Desperately appreciate any suggestions for further troubleshooting.
