I have a 2003 Ford F150 with 4.6L. I changed the time chain tensioners and guides a few months ago. I only removed the valve covers and front cover to access the time chains. Since then the service engine light came on and there feels like a misfire (most noticeable around 1500 RPM, at cruising speed). Truck starts fine.I had misfire codes on cylinder 5, 7, 8. I replaced the spark plugs, the misfire feeling is still there however, the codes are gone. I am getting codes P0405 EGR A Circuit Low, P0171 System Too Lean (Bank 1), and P0175 System Too Rich (Bank 2). My LFTRIM1 is 27 and the LFTRIM2 is -23. Also looked at the cylinder conurbation test and bank 1 cylinders (1, 2, 3, 4) were all 0; on bank 2 cylinders (5, 6, 7, 8) at idle are in negative numbers fluctuating to 0, once the RPMs are above idle they all zero out.Could my timing have jumped marks? If possible what would be the best way to check this?I was told it could be an intake vacuum leak. Can you help?

 

The EGR passages tend to clog up on the 4.6s. Removing the throttle body and cleaning out the passages might be a good idea.

 

Thanks, I'll try that.

 

I removed and cleaned the throttle body passages. They were not clogged but cleaned them non the less. Still having the same symptoms. DPFE sensor voltage test good (4.9 volt supply and 1.0 volt feedback). Feedback voltage did change as the throttle was moved. Applied vacuum to the EGR at idle and the engine almost stalled but recovered. Disconnected the electrical connectors of each injector and coil over and there was a noticeable change in engine idle. More so on bank 1 than on bank 2. Any other thoughts?

 

What are the codes now? Are you still getting the EGR code?

 

Sorry I took so long to reply. I am getting the same codes to include the EGR code.