I've got a problem related to my O2 sensors that I'm hoping someone can help with.

I installed Dynatech Supermaxx LT headers, x-pipe and high flow cats about 6 months ago. I then had a dyno and street tune done by a forum sponsor with an excellent reputation. In addition to the tune, he also deleted the codes for the REAR O2 sensors so that they wouldn't continuously fire off codes due to the high flow cats; This left the 2 FRONT O2 sensors to work normally.

Everything has been running great for the last 6 months; No codes; No problems. Then this week the car began "stuttering" and throwing PCM codes 1133 and 1153. I know that these codes indicate that the PCM is seeing a slow or non-existant lean to rich to lean switching by both of the front O2 sensors. To diagnose the problem, I started with the easy solution. I pulled Fuse #15 which is the fuse for the O2 sensors, and it was in fact blown. So I replaced it (which of course also erased the codes). Then the car drove fine for a while. But later, I felt the car start to "stutter" again, so I pulled over, checked the codes, and both 1133 and 1153 were back. Pulled Fuse #15 again, and it was again blown.

Does this suggest that both of my front O2 sensors have gone bad and need to be replaced? If the O2 sensors are going bad, why would that cause the fuse to blow? And isn't it pretty unlikely that BOTH of the sensors would fail at the same time?

Or is it more likely that there is a short in one of the O2 sensors (maybe caused by a melted wire from the headers?) that would be blowing the fuse, and thus setting the codes? But if its a short in the wires, isn't it pretty unlikely that it would set BOTH 1133 AND 1153? Wouldn't it just set the code for the one sensor with the melted wire?

Suggestions on how I should proceed to solve this problem would be greatly appreciated!

 

Headers probably melted something. Jack it up and look!

 

Melted wires!! Don't ask how I know.

 

Dude im having the same problem with my z i give it gas and it just bogs and stutters i also dont know what to do?

 

Well, as always, members of the forum were correct. The culprit: burnt wires on my O2 sensors caused by my long tube headers.

I got the car up on the lift and found that the wiring harness for one of the forward O2 sensors, and one of the extension harnesses (from the header kit) for the other O2 sensor had been badly burnt. All the insulation was melted away, and the bare wires were burnt and touching one another (which explains why the fuse kept getting blown as well).

So, I replaced both front O2 sensors, and both extension harnesses (had to order new ones from the header manufacturer). Before I installed them, I double wrapped everything with high temperature insulation tape. When I installed them, I was extra careful to tie everything out of the way of the headers as much as possible. I'm pretty confident they won't get burnt again (cross my fingers).

Also, one other thing I noticed. The new O2 sensors that I ordered (from one of our forum vendors) were a little different then the old ones I was replacing (even though the part #s were the same and both were AC Delco). The new sensors had small holes in the outside of the sensor housing, whereas the old ones didn't. I'd read on the forum about many people drilling similar holes in the housings in order to improve O2 sensor performance when using Long Tube Headers. So maybe AC Delco decided to take the hint and improve their design?

Anyways, I'm back on the road, running strong. Thanks again for the help!