I recently put headers on my 318 and didn't reattach the o2 sensor because there was no plug on the header. could this be the reason my truck now misses?

Are you saying you do not have catalytic converters?
If yes, then this is the reason you're getting O2 sensor issues.

You are wanting to put headers on a Blazer? Power to ya, dude! I doubt if anyone can tell you how to do it other than unbolt the existing manifolds and bolt the headers in....hope they fit...

Have you thought about what you are going to do with the REST of the exhaust system? Like the O2 sensors, catalytic converter, etc.? Install headers because it sounds cool and all your buddies will be impressed with all the "power" it gives your Blazer...only to totally mess up your fuel control and have it run like ****???

I don't get it.....

Good luck

Should bolt to the head the same maybe go to studs in engine if possible. The O2 sensor needs to be inthe same distance fromthe head as before. If the sensor area needs to be removed from your system to put in the headers then drill a hole in the collector area and weld in a nut, then screw in the sensor as before

If the truck is fuel injected and probably is the aftermarket headers are sending a signal to the computer and feeding more fuel to the engine fuel is controlled by the intake and exhaust.as for the o2 sensors you will be fine without them they only turn on your engine light when it
has been covered in carbon monoxide to the exhaust.

Your car should have two O2 sensors. One will be located after your catalytic converter. The other one should be located before your catalytic converter somewhere between your headers and your cat. Rarely, on some vehicles, there's a 3rd O2 sensor which is located also somewhere between the catalytic converter and the headers.

Your car should have two O2 sensors. One will be located after your catalytic converter. The other one should be located before your catalytic converter somewhere between your headers and your cat. Rarely, on some vehicles, there's a 3rd O2 sensor which is located also somewhere between the catalytic converter and the headers.

Your check engine light may not be pointing to bad O2 sensors. The light can mean anything from a loose/faulty gas cap to a transmission issue.

This light comes on when the computer detects a fault of some sort in its diagnostic tests. If it keeps detecting this issue, the light will remain on. If the light turns off, then it has detected that the issue may no longer be present.

In order to find out what the exact reason was for your light, You need to have your car computer scanned to retrieve the code that the computer would have stored when the light triggered. Most garages will do this free of charge. The code will tell you what may have caused the light to initially turn on.

You can drill a hole to the down pipe and weld in a nut with the same size thread as the O2 sensor. make sure the nut is stainless and try to have it close as possible to the header's collector. You can also drill it to the header too as close to the header collector's, your preference. Good luck and hope this helps. keep me posted and be glad to help.

The O2 sensors are mounted into the headers. If by aftermarket exhaust you mean a cat-back exhaust system with midpipes and mufflers, then the O2 sensors are a non-issue - they won't be touched. If you are doing cat-back, headers, and maybe high-flow cats, the O2 sensors will just screw directly into the new headers - they'll be set up to receive them.

P1133 - Insufficient Switching on a Pre-Cat sensor, Bank 1 Sensor 1
Is the exhaust stock? or do you have long tube headers?? The long tube headers cause the heat-up time on the o2s to be longer (causing the switch time to take longer (p0133/p0155)).

Otherwise - insufficient switching of the o2...exhaust leak possibly near the sensor... sometimes a blown head gasket can cause this code too.

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The O2 sensor is located in the exhaust pipe prior to the catalytic converter. You'll have to get under the vehicle to see it or replace it.