I have a 1999 f150 5.4 with 154k I picked up on the cheap that was missing on probably 3 cylinders at least, has codes for all 4 o2 sensors and idled up and down. I'm in the process of changing all the coils and plug. I've changed the cylinder head temp sensor, and i have 4 new 02's. I was just wondering if anyone has experienced or heard of something like this, and I'm not getting any other codes and i don't think the new parts will fix the idle or the running rich problem.

 

"Probably missing on 3 cylinders..." doesn't really say much.

Have you scanned the truck for codes? If so, please post them.

Here's my advice, based upon what you provided in your few sentences without codes.

The front O2 sensors have a big part to play with the fuel trim and idle patterns. Barring any vacuum leaks or any issues with the IAC. Speaking of the IAC, I'd clean or replace (with the gasket) the IAC depending on how it looks inside.

I'd get an UNLIT propane torch and start fanning it around hoses in the engine bay and see if that changes the idle.

Not sure why you'd replace the CHT sensor without first confirming it's reading on a scan tool. (They generally run pretty close to the coolant temperatures.)

Lastly, and I don't mean to scare you, but if the previous owner neglected to fix the O2 sensor problem and it ran rich for many miles, the catalytic converters might be destroyed, which can end up breaking the honeycomb material or have it expand and cause a restriction. Which then causes power and fuel problems. Try tapping on the cats with a rubber mallet and see if you hear anything moving around inside them. If you don't, you may still have a restriction, and you'll need to do an exhaust back pressure test. When both of those procedures come back inconclusive or negative, I'd then replace the O2 sensors and drive it until the code comes back. If it does, then it's for sure the cats (unless a massive exhaust leak before the cats, like the headers or manifold collector pipe, but you would hear it loudly).

Good luck.

 

The only codes it had was P1288, P0161, P0155, P0135, P0141, and P01127.

and I read on either this forum or another about the CHT would cause it to shut down 4 cylinders, and the alternator had a bad bearing so when i changed it i changed the CHT while I was there

and I am also sure that the cats are toast

 

If you look at the codes from the lowest to the highest and their descriptions, it tells a story.
135/141/155/161 are [all] Ox sensor open Heater circuits. Obviously, a harness issue or a blown fuse due to a ground -out. Look close to the engine where they are all in the harness together.
1127 says Exhaust is not hot enough to use for testing. May be the cats are totally gone. Can't tell until the 135-155 codes are fixed.
1288 says CHT out of test range. Any attempt to test this sensor cold means nothing if it is cold.
That's all there is to it.
And NO, a CHT does not take cylinders out of operation. It offers coolant temp to the Dash indicator and is used as one of two signals to richen up fuel at cold starts.
Good luck.

 

You rally need to be looking at the live data and see what the fuel trims are doing. The main causes of running rich that I have encountered are bad cht, bad o2 sensors (up stream and down stream), bad maf, stuck injector, and bad plugs/coil leaking exhaust manifold gasket.. Bad maf will act like a bad map and dump fuel. If you have replaced the o2 sensors and are still getting a bad heater code, check the wiring to make sure it didn't fall against the exhaust or get cut on something and is grounding out or broken. You can check for a plugged exhaust by attaching a vacuum gauge to the hose that runs from the egr tube to the dpfe. Should have no pressure or very minimal.
Again, you really need to be looking at the stft's and ltft's.