In my case, P1131/1151 and P0171/0174 were the hint to tear the intake apart and do the intake gasket and isolators. That’s why spraying won’t get you anywhere with this, as you won’t get to them with sprays.

None of those codes came back after that. Didn’t even touch O2 sensors. They are obviously doing their job.

 

Hi banned, I can only speak to the 02 sensors. Assuming your '03 4.2l is the same set up as my '99, there are 2 upstream 02 sensors; on the passenger and driver sides, both low down, near the firewall. On the passenger side, follow the transmission filler tube to the firewall and you'll see it. On the driver side, it's just beyond the spark plug closest to the firewall. Yeah, when I replaced mine my brother-in-law (a mechanic; I was 'assisting') had to heat those sensors up with the acetylene torch, good and hot. The danger is if you don't get them hot enough you could strip them, and then you've got an even bigger problem. Good luck.

 

On my '99 I was getting P1131, P0133, P0171, P0174, and P1132. My fuel pump had to be replaced (it went dead), but after that all codes came back except P1132. As I stated in an earlier post, I got rid of all codes (and none have come back in over a year) by changing the PCV system rubber elbow and the 02 sensors. I think that these codes can be thrown for a number of reasons. I'm not sure if 02 sensors can be tested; if not then it's a cheap repair to replace them and go after the intake gasket and isolators if the codes come back. At 177,000 miles the 02 sensors are likely due for replacement anyway. Mine had only 96,000 on them.

 

Which o2 sensors do you like? Oreilly Auto has a bunch that supposedly fit this truck , several brands and prices go from $63 to $500 each
https://www.oreillyauto.com/shop/b/p...50?q=o2+sensor

Is a plenum gasket set enough or should I get it and the manifold gaskets?

 

I got my 02 sensors from Rockauto. I just got the most basic ones and they've been fine. But I only drive my truck in the summer months and don't put on a lot of miles. You may want to step up a couple of notches if your truck sees heavier duty.

 

O2 sensors are best to go with Bosch or Motorcraft. Get them on www.rockauto.com

 

I dont find o2 sensors for this truck at Rock Auto. Do you?

 

YES

https://www.rockauto.com/en/catalog/...2)+sensor,5132

 

Thank you. I couldnt find it. Those prices are a lot better than Oreilly Auto Parts too