I recently replaced all four O2 sensors, spark plugs and plug wires. In the process I broke a manifold to pipe stud that resulted in a slight exhaust leak. I dropped the exhaust Y, fixed the stud and replaced both gaskets. Now I am getting code P0130 and P0150 and both front sensors are reading 0.00 and its idling rough most of the time. My first thought was vacuum leak but I'm getting a steady 14 lbs with a vacuum gauge from the passengers side PVC port. In the process of changing the wires I loosened the plenum but did not remove it. I don't hear any vacuum leaks and at times it idles normally. When the Rover is cold the front sensors show around .5v but then as it warms up they drop to .0. If its warmed up already when I start it the front sensors always read 0.00. Both the rear sensors read between .8 and .5 depending on engine temp. (All readings and codes are from the UG) The rover also alternates between open and closed loop, more time open. Seems like a slight loss of power as well. Any ideas? Thanks

I'm also wondering about the P1590 code

 

I just went through a very similar experience. What brand O2 sensors did you put in? I got two dead Bosch sensors from Amazon. Chased everything else thinking it could never have been two DOA sensors. Well, it was. Swapped out the Bosch O2’s with Walker’s from Rock Auto and everything cleared up. Truck is running perfect. Hope that helps!

 

If they read .5 on cold start then the 02 sensors are working, and your mixture is actually going lean after that. Sounds like you have a massive vacuum leak.

 

Front o2's should fluctuate regardless. Are there any heater circuit codes? I had a similar situation.

Check the pins again and again. Make sure they are seated in the connectors. Clean out o2 connectors and let dry. Swap o2 sensors as final check.

 

Thanks for all the advice. I’ll keep working on it and post what I find works.

 

That’s exactly what I thought too! Mine did the same thing. No vacuum leak, it was the DOA Bosch O2’s from Amazon. The readings would start out looking good, and then just drop minutes later.