Changed O2 sensor now car doesn't run right

[Warharan]

I have a 96 Talon TSi AWD with a FP3065 turbo and a TiAL 44mm wastegate and av AVCR for boost control, and all other supporting mods, look in my profile. Here's the issue...

My O2 sensor on the turbo manifold went bad. So I took it off, unplugged it and replaced it with a new one. Very simple. The only 2 vacuum lines I pulled off were from the wastegate, one at the very top of the bell part and one on the bottom edge. That was just to make some room to take the O2 sensor off. Once I replaced the sensor and plugged it in, I put the 2 vacuum lines back on. That's it. Very simple, took 10 min.

Keep in mind car was running fine before.

NOW

When I start it is can barely idle, the engine shakes (seems like it's running on 2 cyl.), and it is spewing a very rich gas odor with black smoke out the exhaust. I have no cats but it was never this bad. Then when I gas it no matter how much it only revs to about 2500 rpm and badly at that. WHY???????????????????????????

 

[throwedgsx]

Sounds like you have a faulty o2 sensor. Possibly reading lean mixtures and dumping way to much fuel into the engine. What kind is it and where did you get it from?

 

[silvreclips]

I believe your suppose to disconnect the battery after you change o2 sensors. To let the computer re calibrate all its settings with the new sensor.

 

[Warharan]

Thanks for the quick replies. The one I had on there wasn't working at all. That's why I replaced it. I got 2 spare OEM ones my friend had lying around. Both those, and the original one I put back on again now all do the same thing. I pulled the yellow fuse thingy to reset the ECU. Didn't really help.

I haven't disconnected the battery. I thought pulling the yellow fuse caddy resets the ECU?

 

[silvreclips]

Not sure on that, but try disconnecting the battery for a little while and see if that helps.

 

[throwedgsx]

Did your engine throw a code?

 

[Raph]

Hmm.. did you "tune" on the faulty sensor?and now that everythings right,your whole tune is out of whack?

 

[turboglenn]

I agree with throwedgsx.

But to check, do you have a way to log the O2 output? I've seen the ground for the heater wires go bad on 2g cars before (yellow wire on harness side) mainly when the ECU has been worked over with something like DSMlink or a stand alone has been installed. Not sure why, but they sometimes do. I've had to cross the heater ground over to the battery and have also sent it to the signal ground as well with good results when dealing with a bad heater ground.

Check the wires with a voltmeter, with the key on, the front O2 harness (car side) should have

Red = 12v

yellow = ground for heater

black = signal ground ( not supposed to be grounded to the chassis, but it will show continuity to chassis when tested)

white = signal and there's nothign to read/test unless you tap into it while the o2 is hooked up and working

here's a good post on O2 wiring
http://www.dsmtuners.com/forums/articles-electrical-wiring/244376-oxygen-sensor-wiring.html

Is this happening when the motor is cold or hot? a lot of times ECU's ( not sure on the mitsu one) but they won't read from teh o2 for a minute or 2 during the initial warmup and post start enrichment because they need more fuel due to low air velocity and puddling of fuel in the ports and port walls.

Double check those vac lines, or get me a pic of which ones they were. It culd be that your ECu is re-learning fuel trims after having tehm way out of whack from teh bad o2 sensor.

 

[throwedgsx]

you didn't by any chance mix up your vacuum lines when you put them back on?

 

[Warharan]

Hmm.. did you "tune" on the faulty sensor?and now that everythings right,your whole tune is out of whack?

Ok I did disconnect the battery, same thing. Yes it was tuned on the bad O2 sensor. Could that be the reason, now that the O2 sensor might be working it's running like ass? It SPEWS out a VERY rich smelling black smoke as if it's running extremely rich. Could the plugs be fouled with all that extra fuel? The check engine light comes on.

However, when I put the old bad O2 sensor on, it still running bad.

 

[Warharan]

you didn't by any chance mix up your vacuum lines when you put them back on?

I double checked those. That was my first guess at the problem too.

 

[Warharan]

I agree with throwedgsx.

But to check, do you have a way to log the O2 output? I've seen the ground for the heater wires go bad on 2g cars before (yellow wire on harness side) mainly when the ECU has been worked over with something like DSMlink or a stand alone has been installed. Not sure why, but they sometimes do. I've had to cross the heater ground over to the battery and have also sent it to the signal ground as well with good results when dealing with a bad heater ground.

Check the wires with a voltmeter, with the key on, the front O2 harness (car side) should have

Red = 12v

yellow = ground for heater

black = signal ground ( not supposed to be grounded to the chassis, but it will show continuity to chassis when tested)

white = signal and there's nothign to read/test unless you tap into it while the o2 is hooked up and working

here's a good post on O2 wiring
http://www.dsmtuners.com/forums/articles-electrical-wiring/244376-oxygen-sensor-wiring.html

Is this happening when the motor is cold or hot? a lot of times ECU's ( not sure on the mitsu one) but they won't read from teh o2 for a minute or 2 during the initial warmup and post start enrichment because they need more fuel due to low air velocity and puddling of fuel in the ports and port walls.

Double check those vac lines, or get me a pic of which ones they were. It culd be that your ECu is re-learning fuel trims after having tehm way out of whack from teh bad o2 sensor.

The motor is cold. I let it run for almost 2 min but I start to choke because of all the black smoke not to mention it keeps wanting to die and putt-putts. Here are some picks I just took.

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[throwedgsx]

Have you tried driving it? Do you have any type of datalogger?

 

[Warharan]

Have you tried driving it? Do you have any type of datalogger?

It can barely idle let alone drive. My friend stopped by and said, it's probably the tune. Since it was tunned on a bad O2 sensor and now it has a working one, it needs to be re-tuned. I have one of the guys who tunes for Road Race coming tomorrow to look at it.

 

[silvreclips]

How are you tuning it? I only see the AFC Neo in your profile.

 

[Warharan]

How are you tuning it? I only see the AFC Neo in your profile.

It's got a DSMchip set for 850cc injectors and 91 octane maps. The AFCneo fine tunes it.

 

[Warharan]

For future reference for people, I found out what the problem was.

The car side of the O2 plug was messed up. The insulation was warn and cracking off in some parts and the bare wires were showing (due to years of heat and wear). Anyhow as I unclipped the O2 sensor and pluged the new one on, 2 of the wires touched and when I started the car, it caused a short. It sent 10 volts into the ECU (instead of 5 volts). So we opened up the ECU and viola there was a burn mark right were the pin (for the ECU sensors) meets the circuit board. We fixed the ECU and the O2 wire harness and now all the sensors are in check.