Hope someone can help.

I just installed a new motor.

seemed to be running fine but only put a few miles on it. The one exhaust pipe frpom the left side was sliced under neath the passanger side infront of te cat.

I just had the pipe welded with a flange and took the car for a drive.

Now I get engine code bank 1 position 1 lean o2.

Also now i have a slight sputter almost like a slight miss fire but doesnt seem to be a mis fire.

Could it be a cat going bad or o2 bad or something else?

Im leaning twords the cat sine it did not seem to sputter while the pipe was apart infront of the cat and now since the pipe is connected it sputters.

Any ideas? i already put so much money in replacing the motor i hate to just try and replace the cat if this is most likely not the problem.

My old motor spun a bearing so this is why i replaced the motor. After replacing I did not put new o2 sensors on the car still the originals but they were replaced 1 or 2 years ago so i doubt they are bad but always possible.

Please help

 

Provide basic info, like the year, model, tranny and any major mods. Not all years of the LT1 are the same.

What was the exact code you got on the scanner? I'd suggest possible codes, but we don't know if its OBD-I or OBD-II.

When they welded the exhaust system, was the car's battery connected? Were the O2 sensors installed in the pipe they were welding on?

Did you reset the PCM after the exhaust pipe was fixed? How far have you driven the car since the exhaust pipe was fixed?

 

its a 96 lt1 with auto trans

they welded a flange on the left pipe just infront of the cat.

before the flange was welded on it seemed to run fine but obviously loud .

I got the code 02 bank 1 position 1 lean. not sure the code number I could re check to get the number though.

This is odb2.

I wounder if the cat could be getting clogged. it has a slight hesitation intermittent not at any specific speeds or rpm.

all this semed to happen after the pipe was connected. not sure if its going bad or just reading differently since its connected.

i dont get any other codes.

 

If they welded the exhaust with the sensors in place, and the battery connected, they could have toasted the sensors, or even the PCM.

If you had P0131 = B1S1 O2 sensor circuit low (circuit continuity detects an O2 voltage stationary lean condition).

The sensor is stuck at less than 200mVolts. Could be a short to ground, either internally or in the wiring to the sensor. Swap the left and right pre-cat sensors, and see if the code follows the sensor (P0151) to the passenger side = faulty sensor. If the code stays on the driver's side, its a wiring problem.

 

do you think this could cause the sputtering also?

 

If the sensor is constantly reading lean, due to a short, when the PCM pays any attention to it, its going to add fuel the engine doesn't need, causing it to run rich. Running rich will cause problems with misfires, low power, stumbles..... and I guess "sputtering". In all honesty, I really don't know what a "sputter" is, and how you determined it is "almost like a slight miss fire (sic) but doesnt seem to be a mis fire (sic)".

 

looks like it was my 02 sensor. replaced and its running better