captjasonp

Guys I have had a constant problem with o2 sensors. I have the off road h pipe with all emissions stuff deleted. I have comp cams with long tubes and a bunch of bolt on stuff. My car was not running well and took it to my tune guy and he said niether O2 is reading. I could possibly have a wiring issue. I plan on getting underneath it this week. Anyone have a problem with this before. Both o2 have been replaced.... Figured I would get a few tip before tearing the car apart. car is a 1997 cobra

New to forum looking forward to trading info

captjasonp

update on this i tore into the harness coing fom the o2 to to where is connects under the battery box everything looks to be fine replaced 02 sensors to rule that out problem still exist. Im bidding on a harness on ebay to replace. does anyone know of a fuse or anything else that might tie into the o2 system or any other recommendations to chase tis problem down

Derf00

If you have long tubes do you have O2 extenders? I'd start there, a lot of times they work themselves loose or the connectors push in but the pins back out and don't make a connection.

Don't just start replacing stuff (throwing parts at it). It can get very costly and still not fix your problem.

Check the continuity of the wire from the O2 to as far back as you can go. Also check the input wire at the ECM. Could even be a bad/broken ground.

captjasonp

the replacment 02 I had have a longer wire so i did not have to order the extentions. with that being said the o2 harness looks pretty beat up but no connections that are broken. Im gonna pull it out of the car and ohm check the harness. I hate throwing parts at anything but I wanted to rulle out the o2 so really had no choice. Thanks for the feedback, anyone know of anything that might tie into the o2 sensors to make them not work.fuse etc. I have to belive something is wrong with the harness

captjasonp

Well I took harness out of car and Ohm check the harness. Everything seems to be ok. Im at a loss not sure where to go I have checked everything I know of. Anyone have anymore info I open to try all.

jwog666

you have to check the harness wires with a load, like a light bulb, measuring open circuit resistance will not indicate a high resistance concern. look at it this way a wire is made up of many strands of copper wire that are much smaller, lets say 150 strands per wire, measure the resistance of a good wire and u get .2 ohms, now cut all but 1 strand in that same wire and measure again, u will get .2 ohms. all this tells u is that the connection is not open, now if you disconnect the circuit at the o2 sensor and the pcm and at one end run a light bulb to ground, and at the other jump battery voltage, you can see if the bulb lights up, if it does then no high resistance, if not then high resistance is causing your concern. think of electricity as water in pipes, if the pipe is too small(strands cut) you will drain your sink slowly, but its not a clog. hope this helps

WhiteFoxGT

check your fuses if you havent already

captjasonp

check all fuses they seem ok, put harness in and ran car on a diagnostic tool a buddy of mine had and it shows the 02 are reading something, not sure what number is good or not it was .175 on each and bounces around. Unplugged harness and it goes blank so I would say thats its reading. I think Im gonna get as second opinion on another local mustang shop. I have a feeling its not the 02 sensor. Been through the ringer with performance shops. I believe I have been told they changed and fix things that were not done. Its hard to find a good place to trust anymore.... Thanks guys for all the help

captjasonp

Anyone know what numbers I should be looking for on the 02 sensor on the Diagnostic tool

jwog666

the o2 sensors should be switching between roughly .1 - 1 volt but that will all depend on if the engine is getting correctly metered fuel and is running on all cylinders. i would def get a second opinion, sounds like the first guy didnt know what he was talking about