Doesnt start or hold an idle. Help please
 

A few days ago got a CEL, P0138, high voltage over the rear O2 sensor. Cleared the code and the light did not come back on.

She has been driven since with no problems until last night. My roommate tried to fire her up and she hesitated on the first attempt but then ran fine on the second try.

Today the real problems started, just got a click from the ignition. Assumed the battery was just dead and put jumper cables on it. The engine started but was rough and stalled out. On starting it again and giving it some gas she ran fine until I let off the gas. The RPMS just dropped to zero, it wasnt a stall from a clunk or bang.

Could a bad O2 sensor cause all of this?

The battery has needed a jump 3 times in the past month from running it down (assuming something was left on last night). If the battery is bad could it be the reason the car will not hold an idle?

A bad charging system and a weak battery can cause a lot of strange problems. I would start by having your battery load tested and alt. bench tested and go from there.

I agree with RTorrez1.

It is very likely that you have TWO problems. One is the battery or connections and the other may likely be an oxygen sensor.

Start with removing the battery, cleaning the battery cables and posts until shiny, have the battery "load tested" by any parts store (the only accurate way to test a battery and testing is FREE) and see where you are at.

Here's more on the P0138. I just had it on my 99 and a new oxygen sensor resolved it. I highly recommend NTK oxygen sensors. Do NOT install el-cheapo, no-name oxygen sensors because they are inexpensive. They are absolute total crap.

http://www.obd-codes.com/p0138

+1 this, but make sure you get BOTH sides of the cables if possible.

Seems it was just a bad battery.. upgraded to a 800 CCA battery and seems all is well. The first battery wouldnt hold a charge and after replacing I went back and had the alternator tested, worked just fine.

How about your code P0138? Has that returned?

No codes have come back...

I agree that it was the battery. When my battery goes completely dead in my 99 the computer has to relearn idle and has the starting issues you described

Thanks for the reply 99Classic. Makes me more confident to hear someone else had the same issues and it should be fixed now.

Hows the Bastard pack and ZJ coil/spacer combo ride for you? I currently have a 2" BB with shackle and am thinking of bastards and ZJ to give it a little extra and bring the rear up to level with the front. Is it much rougher then stock?