Exhaust Cross Pipe with O2 Sensor

[coop34]

Hey guys. Is an exhaust cross pipe necessary in order for the O2 sensor to operate correctly? The mechanic told me that my truck is running rough because the O2 sensor needs to be able to read both sides, so he said that I need to put in a cross pipe and place the O2 sensor in the middle. My O2 sensor is currently on the passenger side just below the flange.

My truck is a 70 with a 5.7 L engine from a 90 chevy silverado.

Thanks for the help!

[OJ1988]

No. 3rd gen camaros had them in the drivers side manifold.

[eurospec1]

Originally Posted by coop34

Hey guys. Is an exhaust cross pipe necessary in order for the O2 sensor to operate correctly? The mechanic told me that my truck is running rough because the O2 sensor needs to be able to read both sides, so he said that I need to put in a cross pipe and place the O2 sensor in the middle. My O2 sensor is currently on the passenger side just below the flange.

My truck is a 70 with a 5.7 L engine from a 90 chevy silverado.

Thanks for the help!

No, sorry he is wrong

[coop34]

Thanks guys. Anyone else have thoughts on this? Anyone agree with the mechanic?

[hayhauler71]

My 90 k1500 has only one 02 in left exhaust pipe he is wrong

[coop34]

Thanks HayHauler. Is your O2 sensor located after the y pipe? I have true dual exhaust straight back with no y pipe or cross over.

[Boog]

No disrespect to your mechanic but he needs to pay attention to where the factory mounted them. 90 models were, as noted, up close to the manifold on one side. 02 sensors have to heat up to work proper so mounting them further down the exhaust pipe would give a negative effect.
Your 02 sensor may not be your trucks problem.

[coop34]

Thanks Boog. Don't worry about disrespecting my mechanic. It was the first time I went to him and won't go back. He disrespected me by wanting to charge me $2,400 for a front end rebuild!

[406 Q-ship]

In the TBI trucks from 1987 to 1995, the O2 was on either the left manifold, left pipe, right manifold, or the right pipe in one of those locations. Your mechanic does not know what he is talking about and you should consider taking it to another for diagnosis, if he don't know that simple fact how the heck is he going to figure out what is wrong with the idle. Rough idle can be anything from bad plugs, dirty injectors, vacuum leak (more likily to cause a high idle), bad cap and or plug wires.

[406 Q-ship]

Originally Posted by Boog

No disrespect to your mechanic but he needs to pay attention to where the factory mounted them. 90 models were, as noted, up close to the manifold on one side. 02 sensors have to heat up to work proper so mounting them further down the exhaust pipe would give a negative effect.
Your 02 sensor may not be your trucks problem.

If the O2 is non-heated and placed to far down stream (not getting hot enough) the system will drop in an out of closed loop operation, not causing a rough idle (I guess it might, I have seen stranger things). You can retrofit the heated o2's from the later trucks, the 3 wire o2's still have the sensor wire that will connect to the single wire O2 connection of truck (purple if my memory serves), then the black wire is a ground the last wire gets connected to hot 12 volt ignition lead (this the power for the heater element in the o2).

[coop34]

Thanks 406. My O2 sensor is downstream a little from the manifolds, so it may not be getting hot enough. What year truck has a heated sensor that would work on a 90 TBI? And could I splice off of the starter for a hot ignition lead?