Cat removal / Running problems?

Agtronic · Nov 19, 2008

Hey guys!

I recently did some work on my brother's 1996 Mustang GT. In taking the tranny out, we needed to cut off the exhaust. The car is a winter beater, and is severly rusted. Since we had hacked up everything, we decided to delete the cats.

Now everything is back together, and the car runs like crap. When ever the car is in closed loop, it bucks and sputters and does not want to accelerate. As soon as you hit the floor with the gas, it picks right up and goes.

Is it common for the car to run like crap after removing the cats? Maybe something to do with the back pressure, or did I screw up an O2 sensor in the process of removing them?

I'd appreciate any insight.

Thanks for your time!

smitty1991 · Nov 19, 2008

usally with no cats for instance if you use an offroad pipe with no cats you need to turn off some sensors. we put an offroad x pipe on our 2003 and we had to use a hand held tuner to turn off the front oxygen sensors. i think you may also be able to use a mil elimnator.

Agtronic · Nov 19, 2008

smitty1991 said:
usally with no cats for instance if you use an offroad pipe with no cats you need to turn off some sensors. we put an offroad x pipe on our 2003 and we had to use a hand held tuner to turn off the front oxygen sensors. i think you may also be able to use a mil elimnator.

You have to turn off the front ones? I would think the ones after the cats would 'cause a MIL, but in this case, I spaced them out, which normally always works, and I don't have a MIL ... Weird, it just bucks and stumbles under light load.

2002BLGT · Nov 19, 2008

got a check engine light ? if so pull the codes and post back

Agtronic · Nov 19, 2008

2002BLGT said:
got a check engine light ? if so pull the codes and post back

No check engine.

I unplugged both front sensors, and went for the a drive. Car runs beautifully. And somehow, still no check engine light. Strange. I know the check engine light bulb is good 'cause it lights up when you first insert the key.

So now I'm wondering if one the sensors is bad, or if it's only having difficulty reading the air/fuel ratio because of the lack of backpressure.

Will plug in one and see if it helps narrow down which one is causing the trouble.

Will report back in 10 mins.

Agtronic · Nov 19, 2008

I unplugged the driver side one first, car ran like a champ, then unplugged it and replugged the passenger side, and now it runs like ****. I guess it's safe to assume the driver side sensor is bad ... I wonder how much they are.

Cool, thanks guys!

FordTard · Nov 20, 2008

Agtronic said:
I unplugged the driver side one first, car ran like a champ, then unplugged it and replugged the passenger side, and now it runs like ****. I guess it's safe to assume the driver side sensor is bad ... I wonder how much they are.

Cool, thanks guys!

Went through that same chit with my car 2 weeks ago. They will run you 50 - 65 dollars depending on where you buy them and how long of wire lead they have.

IMO i would swap one of the after cat sensors forward and put the crap one in the back. the back ones are not doing anything important especially with the cats gone. you may need to modify the plug by using a razor blade to trim off some plastic but they work fine. I did this as a temp fix when i was getting my new ones in.

Rusty67 · Nov 20, 2008

With no sensor hooked up the car will default to a basic tune that will run the car but you will have less power and horible gas milage.

Swaping a rear sensor forward is a great idea. I would get some MILs for the rear sensors while you are at it to keep any codes from comming up down the line.

Agtronic · Nov 20, 2008

Yeah, put in a new sensor in the front driver side, and the car runs great now. I guess I broke it when I took it off. (Put an air hammer to it in a fit of rage).

Good call on using one of the rear ones, didn't realize the connector was so similar, I would have done that for sure had I read this earlier.

Now sure what a MIL is, but from my understanding it's short for a spacer pipe that removes the sensor from the exhaust stream? If so, I did that in the rear already.

I'm tempted to post pics of the "custom" exhaust, but fear anyone will associate it with my shop. Hehehe ...

Rusty67 · Nov 20, 2008

Like this:
1996-04 Mustang M.I.L. Eliminator Set - by BBK

5.4ever · Nov 24, 2008

Well since your original question was about your bros cars bucking/sputtering, Ill try and help u there first. When the cats are deleted, wether its via an O/R mid pipe or just cutting them off, in no way will this affect the performance of you r vehicle. It may change the power band(raise or lower torque/HP) but it will not make your bros car act up like you have described. I have deleted many cats from diff. ford vehicles and not once has this happened to me. While I will agree with the statements about moving the 02 sensors up, or adding mils, this has nothing to do with your bros car acting up. All the sensors do is that, sense, or measure the exhaust flow and report it to the ecu, it will not make an engine go into limp mode like many believe. You mentioned you did some other work on it, something with the tranny?? Might want to start there. Retrace yours steps, make sure all was put back together ok

FordTard · Nov 24, 2008

5.4ever said:
Well since your original question was about your bros cars bucking/sputtering, Ill try and help u there first. When the cats are deleted, wether its via an O/R mid pipe or just cutting them off, in no way will this affect the performance of you r vehicle. It may change the power band(raise or lower torque/HP) but it will not make your bros car act up like you have described. I have deleted many cats from diff. ford vehicles and not once has this happened to me. While I will agree with the statements about moving the 02 sensors up, or adding mils, this has nothing to do with your bros car acting up. All the sensors do is that, sense, or measure the exhaust flow and report it to the ecu, it will not make an engine go into limp mode like many believe. You mentioned you did some other work on it, something with the tranny?? Might want to start there. Retrace yours steps, make sure all was put back together ok

WOW, you are way off.

The O2 sensors have everything to do with it. They do not sense exhaust flow and report it back to the ecu. They are measuring the air fuel ratio and tell the ecu if you are lean or rich and then the ecu uses this info to add or take out fuel. So if one is not working right a reporting lean, the ecu will dump a chit load of fuel in that bank, causing the car buck and sputter and have no power.

And I am pretty sure Agtronic already replaced a O2 sensor and fixed the problem.

Dragstr05 · Nov 25, 2008

Agtronic said:
Yeah, put in a new sensor in the front driver side, and the car runs great now. I guess I broke it when I took it off. (Put an air hammer to it in a fit of rage).

You got it! An air hammer will just shatter them apart inside. You will break them almsot every time.

SaleenGT2001 · Nov 25, 2008

FordTard said:
WOW, you are way off.

The O2 sensors have everything to do with it. They do not sense exhaust flow and report it back to the ecu. They are measuring the air fuel ratio and tell the ecu if you are lean or rich and then the ecu uses this info to add or take out fuel. So if one is not working right a reporting lean, the ecu will dump a chit load of fuel in that bank, causing the car buck and sputter and have no power.

And I am pretty sure Agtronic already replaced a O2 sensor and fixed the problem.

no, YOU are way off.

he was refering to the REAR O2 sensors. which do not have anything to do with why the car is running like crap

FordTard · Nov 25, 2008

SaleenGT2001 said:
no, YOU are way off.

he was refering to the REAR O2 sensors. which do not have anything to do with why the car is running like crap

He did not specify which O2 sensors he was talking about and when he said that they have nothing to do with the problems.

True the rear ones would not cause the problems but the front ones most def. would.

Sry bout jumping the gun a bit

SaleenGT2001 · Nov 25, 2008

NP
he was refering to the original problem and the question about removing the cats affecting the cars performance. those front O2's will hurt the car if they are messed up!

Cat removal / Running problems?

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