2002 F150 XLT 4.6L with 147K miles. Farm truck where mice chewed vacuum lines and a some electrical lines. Dust and dirt throughout. Fuel cleaner added to gas on way home. Truck runs rough and has no power.

Vacuum lines and elbows replaced as needed. Vacuum tests good.
Electric lines all seem repaired. I used liquid electrical tape on anything that looked like it could use added insulation.
EGR pulled, cleaned, tested on and off truck. Code was 406.
Throttle body pulled cleaned.
TPS tested good.
Installed new fuel filter.
Fuel pressure tested at 31psi, 33 psi 10 minutes after engine shut off.
Removed PCV valve, cleaned. Seems good.
Ohmed out fuel injectors (tested all except no. 8)-all were between 15.1 to 16.6
Ohmed out coil packs-all were 1.1 or 1.2
Installed new Motorcraft plugs with new Duralast boots and wires with dielectric grease. The truck had some pep for about 2-3 miles then appears to miss again.
Installed new air filter
Cleaned MAF
Installed new DPFE sensor (NAPA Echlin)
Tested exhaust back pressure. pressure OK
Idle is rough, the driver side cat was loud as the honeycomb inside was broken up. Replaced driver side cat.

Prior to installation of the new driver side cat, the mechanic that installed the cat pulled a P0325 code (knock sensor). He said he had the same thing on his '97 4.6L and 8 new coil packs fixed his problem.

I drove home and it still misses and has no power. When I turned the AC on at a stop light, the load stalled the engine. I pulled codes at home and got P0406 and P1507. I pulled the IAC valve and cleaned it but my understanding is I should just replace it so I'll order the Motorcraft replacement. I didn't test the EGR valve, I think it should still be fine. I have a cheap OBD scanner so I don't think I can identify what cylinder is missing.

Does replacing with 8 new coil packs make any sense before attempting to change the knock sensor? Am I missing anything else that could be checked or tested? I don't hear any timing chain noises. Do these engines have VCTs? I don't want to drive too much and ruin my new cat converter.

Thank you in advance for any suggestions.

 

If you have a P0325 code (knock sensor) then you should test the sensor. Lots of videos out there on how to do it.

 

you pulled the entire EGR body out and cleaned it or just the EGR valve ?
Are these the original coils on the truck ?

My coils started to go one by one starting at roughly 70 000 miles....

Misfires, check engine light, no power, etc...

changed them all....

 

I pulled and cleaned the EGR valve, replaced the DPFE, and tested the solenoid. I did not attempt to pull and clean the pipe the runs from the exhaust manifold to the EGR valve that has the two little orifices connected to the DPFE. Is that what you mean by cleaning the whole EGR body? I did pull and clean the whole throttle body.

I don't know if these are original coils. All eight coils have 12A366AA part numbers stamped on them but one bank has the additional numbers 2C1243 and the other side has 2C1242. I don't want to throw parts/money at this but if new coils fix the issue, I can avoid pulling the upper intake and checking the knock sensor. Could the coils still be bad/weak and needing replacement even if they checked out?

 

Even a cheap OBD2 reader should tell you which cylinder is missing. I've had good success with just cleaning the IAC valve. Not sure where to go from here. Good luck with it!

 

I realized after further research that the OBD scanner should be able to pick up a miss. Thank you for confirming.

I replaced the IAC (per code P1507) and it did need replacing. The engine cranks and idles without fluctuating.
I checked the EGR tube to ensure it wasn't clogged and it was good. I replaced the EGR valve (per code P0406) and it too needed replacing.

The truck runs better but still has a rough idle and it's more noticeable when in gear and stopped, like at a stop sign.

I haven't attempted to check the knock sensor yet. Is there any reason to suspect the cam position sensor even without a code?