04 f150 5.4 won't accelerate, runs terrible after tune-up
 

Hello all, first time posting here. Have searched and searched, and have just been playing whack-a-mole it seems.

Have an 04 f150 screw with a 5.4 that has 180000 miles on it. It started running rough, and then when going home a few nights ago, was going 75mph on the hiway and truck started losing power. After a few miles it wouldn't go over aobut 50mph and wouldn't get over about 3-3500 rpms Got it home after a long drive (was about 40 miles from home) and it had several misfire codes - most cylinders listed as misfire, random misfire, and misfire on start-up as well. Also had a code for 02 sensor as well but it hasn't came back since the following work was performed. Decited it was time for a tune up. I've only owned the truck for a few months, previous owner said it ran rough for him, and mechanic replaced a spark plug and coil (just one) so I figured it was time to do the rest anyways. Replaced all plugs (only 3 broke), replace all coils. Test drove it, and it had gotten worse. Cleaned air filter (has k&n from previous owner), replaced fuel filter, changed oil/filter, and also changed out the vtc solenoids - truck was low on oil with very minimal signs of leaking, and would also smoke out the tail pipes if you accelerated hard so my local parts guy suggested it. Truck now runs worse than it ever has. Idles rough, and won't get over 2k rpms when in drive. Only codes it is throwing now are p0174 and p2196.

When in park, it will rev to 4k, then flatten out and surge to 5k for a second or 2 then back down. Driving (forward or reverse) is near impossible now. No power at all and won't get over about 20 mph.

Just let truck idle and searched for vacuum leak with propane tank, no changes at all in motor. Have a fuel pressure guage coming to test that. Is there a way to test the cats other than unbolting them and driving? Figured if it was a clogged cat it would throw a specific code for it

Any ideas on where to go next?

Thanks in advance.

Check the FPDM.

Clogged cats don't necessarily throw codes, go to an exhaust shop to get them tested for backpressure.

When Roadie suggests check the FPDM, he means remove it from the frame and check the backside for corrosion.

I would replace the K&N with a dry filter and clean the MAF sensor.

You are showing rich on bank 1 and lean on bank 2.

I don't think you have a port for a fuel pressure test, you have to read the pressure with an OBD2 scanner, I think it's PID 168c.

Found out it was the cats after all. If they are as clogged as mine were, it will back the exhaust gasses up into the combustion chamber causing it to throw a lean code. I had them removed, and getting a tune tomorrow to take care of the CEL.

I'll probably change the FPDM also, just because of how much I've read about them failing.

Haven't cleaned the MAF or throttle body yet, going to do that in the morning before heading to the tuner.


Thanks for the replies!