Hello everybody,

First off let me say that I am a complete noob when it comes to cars to don't hold my question again me.

I have had a 2006 GT Vert for about 2 years now. Shortly after getting the car, I put on a MAC Prochamber H-pipe Off Road and some axle back flowmaster mufflers.

I love the sound but for a while now... I have feft like there was, lets say, extra noise coming from the bottom of the car like when I am passing by a curb or something where it will echo. It's hard to explain exaclty what the sound is like but to me, it sounds like a really old muscle car.

Since I have an offroad mid pipe, and this may sound stupid, but I thought that the sound I was hearing was just the extra air flowing through the pipes. So maybe that was the reason for the extra sound.

Well I went to get my car inspected and the guy passed me... but also knew my car was illegal. We got to talking and he was telling me about why and how my MIL's worked (since I had to have them put on to stop the check engine light from coming on).

He was telling me that over time, if i am running too lean or too rich, it will damage the engine which is why the censors are there to help regulate the air/fuel mixture. When I put on off road pipes, it will change the air flow and cause that mixture to be wrong which is why the check engine light comes on and why I have to fake the computer into thinking everything was ok.

So I got to thinking.. .crap... maybe that sound is the engine going bad or something along those lines.

Have I damaged my engine? Is he just blowing the problem out of proportion? Should I get catted pipes asap?

Thanks for the help.

 

You should get a tune. ASAP.

 

Ok, I'm a noob... but Even I know you need a tune.

 

Ok so just take it to a performance shop and get a tune.

Is there anything else i should ask for? Does anyone know a good shop in the Charlotte, NC area and do you think i am screwed up my engine permanently?

Also, let me ask this... since it's probably going to cost me alot of money for a tune... what if i put my stock pipe back on and took off the MIL's or do i still need a tune regardless?

 

You would have to have some serious fuel issues to damage the engine. Washing the rings is about the worst I can think of in terms of what "could" happen but it would have to be extremly rich(to the point you couldnt even drive/start it)

 

Ok whew... I was like crap... but i think i found a place in my area for a tune. Question though... i am about to take it in for the 30k mile service in another 5k miles, should i worry about having my own 'tune' and those pipes installed? Will they try and fight me if someting goes wrong? Or should i just throw the OEM's back on?

 

You put the Mils in the right spot, right?

 

In theory what he was saying could happen, unlikly, but could happen. Get a tune and you will be safe.

The dealership is probably going to give you the old you VOIDED your warranty by installing the pipe and MIL's.

Your MIL's have to be conected to the rear set of O2 senors.

 

As far as i know i put them on there correctly. I placed them in front of where the Hpipe [] area is. Just in front of that. Should they be more to the back of the car? I didin't notice a place there for them but then again, i never really looked when i put on the flowmasters.

 

Mustangs have TWO sets of O2 sensors. The first set measures the a/f. The second set measures how the cats are performing...

Since you don't have cats, you don't need the second set, hence the Mil eliminators. You car would not run at all w/o O2 Sensors.

Each set of sensors is read differently by the car. I guess you could have used the wrong set, but I can't see how the car would run at all.

As far as the funny sound when rising along a curve, does it sound like a tapping noise? That would be an exhaust leak most likely.

 

No there is no tapping noise or anything like that. It just sounds like more airflow. Its hard to write out how it sounds. I will have to get the DV cam from work and record the sound.

I did prop up the car and check for air leaks with my hand and with soap/water mix but I didn't see any. That was a while ago though so maybe one has developed.

As far as the MIL's go, there was only one place where O2 sensors would hook up to the pipes. That spot was just after the pipe comes off the headers and travels down, then curves to become parallel with the bottom of the car. Since there are no other pre drilled holes for any sensors, I assume it was the right spot.

Thanks for the replies. I am calling around today to find out who can do a Dyno tune for me. Any idea on how much this -should- cost me? So I know if I am getting ripped off or not.

 

I have had 2 prochambers now on 2 different gen mustangs. There should be 4 holes to screw in your 02's. 2 more towards the top, and 2 towards the middle. The eliminators should plug into the 2 in the middle. Now, what I was told is that the eliminators only keep the light off. But the car is still running in limp mode as if the light was still on. I don't know if I believe that, but was told that. Your not going to damage your car by putting in a different mid pipe. All a tune with a hand held tuner is goign to do is completely turn off the rear 02's. A dyno tune with hand held tuner should cost you around $550-$600. But you get to keep the tuner. I notice all prochambers had a metal tinging sound off of curbs and concrete walls. Its just your exhaust merging in the Box. I wouldn't worry about it. If you ever floor it in 5th. Hear how bad that sounds. But you never heard that before with the old Hpipe did you? IMO, Its just the harmonics of the prochamber. If it helps any, I have an 06 that is tuned and I have wierd interior noises from my prochamber.

 

Sorry but I though that this thread was relevant to a problem I had before but I just want to get the facts straight.

I have an 02' saleen and what I did was I had my stock bassanni x pipe's cats sawed off and had the exhaust guys weld in same diameter pipes in place of the old cats. After that I got the check engine light and my engine was running like ****. The idle was all wrong and whenenver I accelerated there was no power or anything. What I did was I got a chip that turned off my O2 sensors

What I want to know is that even though my car is running well, am I still running too rich or lean without a dyno tune? or am I fine.

 

The car will run, Ive seen it happen on here and in person. People need to know what they're doing before they start messing with their cars.

 

recently i had a exhaust leak before the first o2 sensor on the passenger side. who knows how many miles my mom put on the car with the leak. i fixed the leak car ran fine for a couple hundred miles and out of no where i started loosing power on the top end real bad. i checked my plugs and all of them on the passenger side were white with soot...running way too rich fouled them out and got spark blow-out with 12 psi. your o2 sensors are meant for something. my car is boosted too so if it was the other way around than i would of blew something up. thats why i have a wideband to install now.

 

You'll DEFINITELY know when there's a problem. Something dramatically different is never too hard to find.

Get a tune, check the AF and enjoy your car.

 

I will jack it up and look again tonight when I get home. I didn't install the mid pipe, just the axle back. The guy probably hooked up the back ones. I dont remember. Not sure if this makes a difference but i do have the off road pipe. Not the high flow catted one. I might have said that wrong in my first post.

Again, thanks for all the help. You all rock.

 

I am by no means an expert and the Tweecer guys could talk for days about this but this is the basic understanding that I have.. All OBD2 compliant cars have at least 1 pre-cat O2 sensor and 1 post cat O2 sensor. In the case of a true dual exhaust (like our Mustangs), then you would have 2 pre-cats (one on each side before the catalytic convertors) and 2 post cats (one on each side after the cats) or in OBD lingo Bank 1 and Bank 2.

The pre-cat O2 sensors are what take the readings to help the ECU keep the engine run in the correct A/F ratio and also acts as a reference point for the emission reading for.. the second set of O2 sensors after the catalytic convertor. The second set of O2 sensors read the oxygen levels after they've blown over the catalyst and they MUST read that there is a higher % of O2 in the exhaust air than was initially read by the front O2 sensor.

So to summarize, the computer takes a voltage signal from the front sensor (relative to the amount of oxygen in the emission) and compares it to the voltage signal from the rear sensor. If it increased within the correct, pre-defined parameters, then the computer knows that the catalytic converters are still there and working like they are supposed to. If the voltage readings are too close or too far apart, then you get a check engine light (in the case of off-road pipes, the readings would theoretically be identical). MIL eliminators just send a fixed voltage signal to the ECU that should be within the acceptable range of the front O2 sensor to trick the computer into thinking all is well with the catalytic convertors.

I make no guarantees as to the accuracy of this information, it is merely how I have deciphered the information I have read so that I could understand it.

 

the specific strategy of the processing from front to rear sensor data is pretty close to that but the overall gist of it is correct. The rear o2's only exist to sense converter efficiency. They're there to tell you if your emissions system is working correctly.

You should really consider putting cats on the car. Off-road pipes add maybe 3hp over a high flow cat but the cat really does help keep the air clean. 3hp is not enough to feel or even to show in your 1/4 mile times.

 

Its sound in my case.

 

I changed my oil tonight and took the time to check around. What i found suprised me. There is only one sensor hole that i could see. So i went to check my stock midpipe and mufflers and the stock pipes have a sensor hole drilled RIGHT into the cat. Thats it. Weird huh?

 

I have a 2006 mustang gt and I have 4 02 bungs. Theres 2 before that cats and 2 after, well 2 per side of the pipe. A total of 4 holes. Even on my off road prochamber there is 4

 

All my mine has is one as far as i can tell. I will take some pics.

 

hey im in concord NC and if you have not already been to a shop to get a tune i would suggest harris racing or some people go to custom performance but im not a big fan of C.P.

 

I agree with you. The second bank (rear) 02's are only to tell your car if your cats are doing there job. that is all they do.