1999 Expedition 5.4L 4x4

I put a new head on after previous mechanic messed up spark plug hole trying to fix a blown spark plug.

Truck ran fine for 2 days after the job.

Now I get a P0175 code (System too rich bank 2.)

After awhile I end up with a P1152 code (Lack of H02S21 SWITCH - SENSOR INDICATES RICH.)

I also had misfire codes on cylinders #4 & #5. I replaced the COP on both cylinders and I haven't had the misfire codes since.

I have checked compression in Cylinders 5,6,7,8 and they were all good. I checked more vacume lines than I can imagine, including PCV. I checked all spark plugs on bank 2 (drivers side) and they all looked good. I had an exhaust leak at the exhaust manifold and put new gaskets on it. Exhaust leak fixed. I replaced the upstream O2 sensor on bank 1. Oil level is good and not milky and it doesnt smell like gas. I even changed the MAF sensor with one from my parents expedition.

Fuel pressure is at 25 PSI. when KOEO and its around 28-30 PSI when KOER. If I remove the vacume line from the fuel pressure regulator while its running then the fuel pressure goes up to 40 PSI when KOER.

I don't know what else to do because I feel like I've checked everything, including the list of things to check for code P1152. It runs like crap because the computer is trimming the fuel back (-20%) so much that it runs like its out of gas because it is getting a high rich code.

Also, O2 sensor on bank 1 switches from a low Mv (around 122-356) to 1666Mv on my scanner.

Any ideas... I'm willing to try anything to get this truck running right again.

 

The P0175 code indicates a misfire or a leaking injector. But the P1152 code suggests a bad O2 sensor, all on the driver's side.

H -Heated
O2S -Oxygen Sensor
2 -Bank 2
1 -Sensor 1 (upstream or pre-cat)

 

Was the head you replaced on bank 2 as well? New,reman, or junkyard? I would think maybe cam timing but that wouldn't explain why it ran well for two days. Do the spark plugs on the left hand bank show rich? Also maybe a running compression test is in order.

 

Yes I replaced the head on bank 2 with a re-manufactured head. I don't think it would be a timing error since it ran fine for two days. I am leaning towards a leaking injector/misfire problem.

Does anyone know if there is a way to test the injectors to see if their bad before replacing them?

By the way the spark plugs looked normal but that's not saying I wont replace them just to eliminate that from my problem.

 

I would also check to make sure all the spark plugs are working and the wire (going to the plugs) are indeed plugged in. Does the truck shake?

 

Yes it does shake but the Long Term Fuel Trim is around -25%. This is basically what the computer is doing to compensate for an "OVER RICH" condition.

I'm changing injectors today along with coils and spark plugs. I will let you know what happens.

Please feel free to post if you have anymore ideas why I am throwing a P0175 code.

Thanks