o2 eliminators (90)
- Thread starter Jimde
- Start date
Dump the codes to find out what is really wrong. That will save you time and money...
Dumping The computer diagnostic codes on 86-95 Mustangs
Revised 19-May-2009 to update drawing for dumping the codes on 86-88 Mustangs with no check engine light.
Dump the codes and see what the computer says is wrong…Codes may be present in the computer even if the Check Engine light isn’t on.
Here's the way to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great. You watch the flashing test lamp or Check Engine Light and count the flashes.
Be sure to turn off the A/C, and put the transmission in neutral when dumping the codes. Fail to do this and you will generate a code 67 and not be able to dump the Engine Running codes.
Dumping the Engine Running codes: The procedure is the same, you start the engine with the test jumper in place. Be sure the A/C is off and the transmission is in neutral. You'll get an 11, then a 4 and the engine will speed up to do the EGR test. After the engine speed decreases back to idle, it will dump the engine running codes.
Here's the link to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great. You watch the flashing test lamp or Check Engine Light and count the flashes.
See Troublcodes.net Trouble Codes OBD & OBD2 Trouble Codes and Technical info & Tool Store. By BAT Auto Technical
If your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.
The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.
89 through 95 cars have a working Check Engine light. Watch it instead of using a test lamp.
The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.
WARNING!!! There is a single dark brown connector with a black/orange wire. It is the 12 volt power to the under the hood light. Do not jumper it to the computer test connector. If you do, you will damage the computer.
What to expect:
You should get a code 11 (two single flashes in succession). This says that the computer's internal workings are OK, and that the wiring to put the computer into diagnostic mode is good. No code 11 and you have some wiring problems.
Codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.
Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.
Alternate methods:
For those who are intimidated by all the wires & connections, see Actron® for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Wal-Mart.
Or for a nicer scanner see Digital Ford Code Reader (3145) – It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $30.
Dumping The computer diagnostic codes on 86-95 Mustangs
Revised 19-May-2009 to update drawing for dumping the codes on 86-88 Mustangs with no check engine light.
Dump the codes and see what the computer says is wrong…Codes may be present in the computer even if the Check Engine light isn’t on.
Here's the way to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great. You watch the flashing test lamp or Check Engine Light and count the flashes.
Be sure to turn off the A/C, and put the transmission in neutral when dumping the codes. Fail to do this and you will generate a code 67 and not be able to dump the Engine Running codes.
Dumping the Engine Running codes: The procedure is the same, you start the engine with the test jumper in place. Be sure the A/C is off and the transmission is in neutral. You'll get an 11, then a 4 and the engine will speed up to do the EGR test. After the engine speed decreases back to idle, it will dump the engine running codes.
Here's the link to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great. You watch the flashing test lamp or Check Engine Light and count the flashes.
See Troublcodes.net Trouble Codes OBD & OBD2 Trouble Codes and Technical info & Tool Store. By BAT Auto Technical
If your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.
The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.
89 through 95 cars have a working Check Engine light. Watch it instead of using a test lamp.
The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.
WARNING!!! There is a single dark brown connector with a black/orange wire. It is the 12 volt power to the under the hood light. Do not jumper it to the computer test connector. If you do, you will damage the computer.
What to expect:
You should get a code 11 (two single flashes in succession). This says that the computer's internal workings are OK, and that the wiring to put the computer into diagnostic mode is good. No code 11 and you have some wiring problems.
Codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.
Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.
Alternate methods:
For those who are intimidated by all the wires & connections, see Actron® for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Wal-Mart.
Or for a nicer scanner see Digital Ford Code Reader (3145) – It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $30.
You def want to put them back in. O2's are one of the key sensors in an EFI setup. No reason to delete them
so on a OBDI system they will definitly effect the way ot runs if there not in? peace
john
so on a OBDI system they will definitly effect the way ot runs if there not in? peace
john
The front O2's (or the only O2's on an OBD-I car) definitely affect the way it runs in a huge way. On a fox III without O2's, it runs in FMEM and rather rich.
Basically they monitor the mixture downstream and adjust fuel and timing off too lean or rich. At WOT they are ignored and the car runs on preprogrammed curves. Typically when they fail (or get removed) the car runs in a "safe mode" and runs rich.
With OBDII Mustangs, the rear ones are commonly turned off, but fronts must stay. This is done through the computer though...not just by unplugging them.
But like i said, at WOT they get ignored and the car goes on it's programmed (or your programmed) tune
blackened88lx
Active Member
My car recently developed a bad misfire under cruise which would go away above 3k or at wot. This is the only area that o2 sensors don't work, so I unplugged them and it fixed it, and it runs absolutely perfect. Not sure if it would be different because it's an '88 speed density car, but it did not affect the way the car runs at all. It's always been a little rich, and they always stink with no cats, but it seems exactly the same, if not better than it ever has.
With them unplugged, you are safe mode. It will run the mix on the fatter side of things.
To be honest, your initial prob may not be o2 related at all, but by forcing safe mode, the offending sensor input is ignored so that is why the car runs better.
Unsure if the PIP is ignored in safe mode.
I'd plug the O2's back in and run the check engine codes. I'd also be looking closely at the TFI/PIP.
Unsure if the PIP is ignored in safe mode.
The PIP is never ignored. If it were, the car would not run.
blackened88lx
Active Member
With them unplugged, you are safe mode. It will run the mix on the fatter side of things.
To be honest, your initial prob may not be o2 related at all, but by forcing safe mode, the offending sensor input is ignored so that is why the car runs better.
Unsure if the PIP is ignored in safe mode.
I'd plug the O2's back in and run the check engine codes. I'd also be looking closely at the TFI/PIP.
Hmm, possible I guess. I have another set of o2 sensors that I thought about throwing in but it's only gotta last me a couple more weeks. It's all being changed soon anyway and will be tuned for no o2 sensors.
i know when my o2 sensors are going bad the car runs like dogs**t and my wideband does all kinds of funky stuff...
Even at WOT, the wideband goes crazy, it will go WAYYY lean, then just stop reading. I thought it was the WB sensor, but as soon as i replaced the factory o2's it was OK again
Even at WOT, the wideband goes crazy, it will go WAYYY lean, then just stop reading. I thought it was the WB sensor, but as soon as i replaced the factory o2's it was OK again
Similar threads
