98 2500 5.9 gas
dropped a crate engine in about 18k 2 years ago now has been running like a top every since, other than an idiling issue that came along so I replaced the throttle position sensor an idle air valve with cut rate auto parts problem went away well 2 months later problem comes back I go warranty out the TPS, the problem goes away again. Until recently the problem seemed to progress so I bit the bullet an bought the 140$ sensor from the dealer an things seemed to be going good. Up until the check engine light comes on an truck runs like crap, ended up being the upstream o2 sensor so I replaced it at this point the truck is running great seems to have more response (maybe it was just me wanting it to) 4 days go by an I get another light for the same 02 sensor I thought it was odd because truck ran fine this time. So I warranty out that o2 sensor truck seems to be doing great for that day. I take it yesterday an truck doesn't wanna stay running it's trying to spit an sputter out. I can throw it neutral an rev the engine a few times an drop it back into drive an get further down the road an it no longer spits an sputter for about 45 seconds then does it again.

So my question for the forum is what may be going on here?
Wouldnt it tell me if I was loosing an injector (s) ? Is it possible the down stream o2 sensor is not able to give an accurate reading compared to the upstream sensor an it's throwing my truck out of wack?
Does this seem like a fuel pump on its way out?
I can cold start the truck and it WILL run fine for about 15 minutes or so. Which leads me to believe a fuel air ratio is off.
I currently have no codes stored in my computer.

Also every since I have done the engine if I am sitting at an idle in park an rev the engine to 3500 rpm a few times an let off the truck rpms drop below the running 800 rpms like it wants to die but it won't. (Like an old carburatored engine getting flooded out) ive never paid much mind to that tho hopefully it won't come back an bite me in the ***

 

Disconnect the front O2 sensor, and drive it like that for a few days. if the problem is gone..... need to check the wiring for the O2 sensor.

Also, if you are putting Bosch O2 sensors in there, that might be the entire problem.... Denso, or NTK only please.

 

It is a Bosch unit,. Had no idea not to use the brand.

 

Yeah, replace it with NTK, or Denso....

 

Problem seemed to go away instantly well I noticed it right away anyhow. It now idles just fine. If I'm coming out of drive into park the idle will drop a lil low for a second then pick back up an idle just fine I assume that is because it's not able to get a reading at the o2 because it's unpluged right?

So I'm probably not having a wiring issue here then, since j unplugged an it runs fine. It more thank likely is a Bosch issue?
Or should I be looking for a. Wiring issue?

 

Replace the sensor with a Denso, or NTK sensor. See if the problem is solved. (Be sure and clear codes as well....)

 

Well I replaced it with ntk sensor, and it instantly ran like crap. So this means I have a wiring issue?
how does one begin to go about tracking this issue down?
Do I start looking for certain volatage at the plug in?
Do I get the tranny out of the way an try an identity a split in the wire?
Could it be on the PCM side?
What happens if I leave 02 unplugged for a period of time?

 

Reset the PCM. Just disconnect the battery for 15 minutes or so.

 

Ok will do.
I have a hypertech power programmer I currently have set to run 93 octane. Once I reset the PCM that hyper tech time will be gone right? At that point I'll be back to stock again right?

 

Nope. You will still have tune, the PCM will simply forget everything it has learned since the last time the battery was disconnected. When you flash your pcm with a new tune, it gets written to non-volatile memory. Only way to go back to stock tune, is with your programmer.