Sorry for the long post. Here are the basics, 2002 F150, 4.2 V6 2 wheel drive, Auto with 96,000 miles. I had a post for other problems, but I am wondering if they are all linked. Started with P1151 lean code, loss of fuel mileage and HP, changed Bank 1 H02 sensor, plugs, air filter and fuel filter. Then started getting P1131 and P1151 Lean codes. I have changed the MAF, and still got codes. Finally cleaned Idle Air Control because codes came when idle was rough, and the codes are gone. Still don't have fuel mileage or HP back completely. Around the same time as these codes coming up I started to have a vibration at highway speeds. Now that the codes are gone vibration is still around. Had tires all checked and balanced today, but it seems to be when I am accelerating or holding the gas steady. Let off the gas and the vibration is gone. It is vibrating the whole truck, floor and steering wheel. I am thinking about the upper intake gaskets for the Gas Mileage and HP, but don't know if that will fix it or if it is something else causing the vibration too. Help on one or both needed very badly. I feel like I am driving the Walmart paint shaker down the road, so please help.

 

As a shot in the dark, check out my post. Might be a vacum leak. I replaced two elbows on my fathers 4.2. One undr the front of the intake and the other was on the rear passenger side of the intake. Leave it running and reach in moving your fingers over the elbows. You will know if you hit the right area and plug the hole if there is one there.

 

You may have replaced the wrong 02 sensor, code P1151 is for bank 2. I also would check the function of the EGR. Just had another thought, I have seen the cam timing off on the 4.2

 

Thanks for replying. Sorry, I think I wrote the wrong bank number, I did change bank 2, I just got looking back at my papers, and I also had the EGR checked at the garage and was told it was fine. I am going to go check those elbows right now. I am really hoping to find the problem with this. I am almost 500 in the hole on this between the garage and parts...thanks again. Any more ideas would be great.

 

You do know that P0131 is for bank 1 02 sensor. If you don't find any leaks, I would find someone with a scanner that is capable of looking in Mode 6 [monitors] and see what is going on.