I removed my rear cats last week, and was throwing the P0156 code a couple times a day. After i did the gotts o2 mod to the o2 sensors, the light stayed off for around 150 miles, (2 days) but then came back on. Could anybody tell me any possible reason why? Could it possibly be caused by leaks where the new pipe was put in?

 

The last time I had that code was because of a leak right at the 02 sensor bung. Do you not have cats at all? Check for leaks around all the welds after the upstream 02.

 

x2, double check leaks. Sensors are very sensitive to leaks. Speaking of sensitive, did you touch the sensors? Oil from skin is enough to trip them, and contamination at all will do it. How many miles? Could be time to replace them even. I'm betting you have a california emission model truck ( LEV ).

He only removed the rear cats.

 

It is definitely leaking where the new pipe was put in, but i was unsure of whether that would set a CEL or not. Bringing it to the shop today to get a quote of dropping down the system, replacing the leaky drivers side precat, and patching all of the holes. If that doesn't work I will replace the rear o2 sensors and see what that does for me. If they are as sensitive as you say, then they may have been damaged when i removed them, since they did not come out very easy before i used the torch. Thanks a lot for the help guys.

 

Well, no good news today. The garage said since i already messed with my emissions, they wouldnt touch my truck without replacing the manifolds, downpipe, cats, the whole deal, which they said would be a couple thousand. They suggested that i try to find a parts truck or just a manifold back system to buy and swap it out. But im thinking, why pay $500+ for a parts truck just to get a rusty old restrictive stock exhaust system which is what i started out with, and pass up the chance to get a few more hp for a bit more money? What i would like to do is get long tubes, high flow cats, and a new y pipe that will all fit together without much modification, and run the rest of my exhaust system from there. But i cant seem to find much for any of that sort of set up for a 98 f150. Any advice anybody? Part numbers or even website links would be a big help. Thanks very much. Andrew.

 

Find a new shop!!!

They are not allowed to remove emissions equipment, BUT they can work on what is ALREADY there. All they are doing is fixing a leak on an exhaust system.

 

Part of the problem is there is a big hole in the system right next to the drivers side flange in between the precat and the manifold. So they said they would have to replace everything and that it wouldnt be worth just patching the holes. So if I'm going to replace everything, I might as well do it right. I read on here you could run OBX longtubes meant for the 99-03s on a 98 if you change the EGR tube? Can anybody tell me what this consists of or if it is worth it?

 

That shop is a crook, you could just as easily re-work the area that needs fixed, but you are on a much better path with the LTs and hi-flows route. Hope you get it all figured out and done.

 

You need to find another shop then. The shop out here will tell you if you want an exhaust without cats, to cut off your cats and drive the truck to them like that, and they can work on it from there.

 

^^^^That's how most operate!