'98 F150 4x4, 5.4. Truck was originally equipped with Romeo 4.6. Present engine is 5.4, also '98. Has rough idle and sometimes dies. Replaced bad IAC. Helped some. Cleaned MAF. Started it with MAF disconnected and it didn't turn on check engine light. CEL does turn on with key on engine off so bulb is good. Wondering if anyone can tell me if it is normal not to have CEL with MAF disconnected.

Has 5 Star custom tune on 4.6 pcm. Coil pack ignition. Checked for vacuum leaks. Replaced PCV valve and hoses. Also knocks when accelorating quickly.

Suggestions?

 

If it has a custom tune loaded, there's no way to know what all was fiddled with.

 

May be time to call 5 Star to see what they can tell me the lack of check engine light.

 

Talked with 5 Star yesterday. Check engine light is enabled on the tune I have.

 

Take it back to stock and re-test. There's no way we can try and guess what's actually going on in any tune.

 

Good idea to take back to stock tune and retest. Didn't know if anyone had MAF disconnected without check engine light and could point me in direction to diagnose.