3 Inch exhaust install and running rich & rough

[ReconRob]

So, I made the leap and had a custom 3 inch stainless exhaust (less CAT) installed. Now it runs rough and is running very rich. After researching this issue on this forum and some others, my thoughts are:
1. Sounds like it is the 02 sensor, since the car was running great before exhaust install
2. my service provider cut the wires to the O2 sensor and wires are just hanging out under the car
3. O2 sensor was junked with the old CAT

My questions are:
1. Is the O2 sensor the issue?
If so, do I just hook up a new one and secure it somewhere?
2. Other suggestions what other issues could develop from exhaust upgrade?
3. Would ECU upgrade help with power / fuel control after run-ability issue resolved?

Thanks in advance for the assistance. See you at Z Nationals this year.

[evildky]

What exhaust shop would just cut off an O2 sensor and discard it? Seeing that you are local I'd really like to know. No reputable automotive should would do this, I suggest you find another shop to fix the problem they caused. You'll need someone to weld in an O2 sensor bung and to wire a new o2 sensor to the wires the others haphazardly cut off. Any competent exhaust should should be able to handle this. I'm not a fan of the cat delete, there are great affordable high flow cats available that will keep you legal and keep black suit from collecting on the back of your car.

1. Yes, when the O2 sensor does not send a signal the ecu assumes lean and adds fuel causing a rich condition. This is they way they have worked from the beginning which is why any shop that would simply cut it off and discard it has no business working on anyones cars.
2. None. unless someone mistakenly buggered something else in the process, given that they cut off the O2 sensor all bets are off, who knows what else they screwed up.
3. If the car ran fine before the "upgrade" it should run fine again after no tune needed. If you add an intercooler and start turning up the boost and get to the point that you run out of fuel injector a tune will become necessary.

The local Z club (Bluegrass Z Car Club) will meet 5/18 at Collins Nissan at 6pm. I think a couple of us are headed to Z days next weekend, A few will be going to Z Fest in Branson at the end of the month, Several of us will be attending Z CON in Memphis in July and then a couple will likely attend Z Nationals in September. I also am at just about every local autocross as I am the solo chair for the KY region.

[ReconRob]

I will be checking it out today. It is not for sure if they actually cut the O2 sensor off and chucked it. But, since it has been running poorly and been trying to track down the issue. I got the car back in the fall and parked it over the winter so this is the first opportunity to find out what is going on. From how it is running it seems like it is in safe mode. Today, I am going to check the codes before I jack up the car and take a look underneath to see what the deal with the 02 sensor is.

Since you are from the area, are there one or more credible "Tuner" shops around. I am originally from the Indy area and just moved my family and business to the area. I will be joining the Bluegrass Z group soon. I was apart of the Indy Z Car club for years. I kind of dropped out of the Z car scene because of business responsibilities. Now, I am ready to get back into it. So, you will be seeing me soon. Also, I have a shop, Recon Master, doing paintless dent repair and other car stuff. It is actually a training center for PDR so it is set up for classes so it may be a place to do a Z car clinic. My son Ethan is a detail industry guru so he is a good one to tap on cutting edge car detail information.

I will keep you posted on what I find out on the Z today. I hope it is an easy fix. I will be pretty Torked if the shop actually didn't make a bung hole and put the 02 sensor in the new exhaust. Your welcome to text me offline to chat about this issue or talk Z car stuff...502.272.0022.

[evildky]

Most "tuner" shops are short lived and don't mess with older cars. If you want a 1000 whp Z33 Dynosty is a huge 350Z tuner in town and nationally but they won't touch a Z31. There are some other shops that likely could handle whatever you need but no one around here messes with older Z cars.