Open loop stumble

Cory · Feb 22, 2018

Hey so I am trying to troubleshoot a 2000 5.7 2500 5spd, the truck runs fine until I shut it down for 5-10 min and then I fire it back up and it is in open loop working its way to closed loop, which is all fine but when it is in open loop it stumbles bad , soon as closed loop kicks in it runs fine, I can put a scan tool on it and switch from closed to open loop and same damn thing stumbles, IT THROWS ZERO CODES!

Only things not replaced are 02s,fuel spider, and pcm

Any thoughts?

chipskittles · Feb 22, 2018

Definitely replace those O2 sensors, with something not Bosch.

Stokes1114 · Feb 22, 2018

O2 sensors have nothing to do with open loop. O2 sensors start correcting fueling when in closed loop.

Supercharged111 · Feb 23, 2018

Stokes1114 said:
O2 sensors have nothing to do with open loop. O2 sensors start correcting fueling when in closed loop.

Yes and no. O2s contribute to open loop fueling with LTFTs, STFTs are what control closed loop and slowly build LTFTs which are added to both open and closed loop fueling. Here I agree though, seems unlikely that the O2s that seem to help are to blame. OP what are your fuel trims doing?

chipskittles · Feb 23, 2018

I had it backwards, my apologies. Yes, closed loop is where O2 sensors are important. That said I would verify good ground straps at the intake, back of heads, body, etc. And disconnect the battery and reset the computer.

Open loop stumble

Cory

Newbie

chipskittles

I'm Awesome

Stokes1114

I'm Awesome

Supercharged111

Truly Awesome

chipskittles

I'm Awesome

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