Engine won't switch to closed loop, need help

[sloppydawg123]

I have a 97 4.3 vortec, and it never closes the fuel loop. Also it is running lean in the open loop according to the o2 sensors. The truck hesitate when first trying to accelerate and the idle moves around a bit, but runs fine other than that.

What makes the fuel loops close?

[MT-2500]

Originally Posted by sloppydawg123

I have a 97 4.3 vortec, and it never closes the fuel loop. Also it is running lean in the open loop according to the o2 sensors. The truck hesitate when first trying to accelerate and the idle moves around a bit, but runs fine other than that.

What makes the fuel loops close?

Engine tempt going to normal 195 and 02 sensors kicking in full operation.

Fuel pressure good?
Any codes or check engine lights?
Mileage and last tune up?

[sloppydawg123]

Haven't checked fuel pressure, was trying to figure this part out first. I just bought the truck, only 86k miles, has new plugs cap and rotor. Engine temp going to around 190, and it has the code for no activity on o2s21.

The scanner reads
o2s11 .05
o2s12 .0215
os213 .400
os221 .440

All of the st and lt ftrm are always 0% and it says fuel system 1 and 2 are always open

[777stickman]

Keep in mind that what you read for engine temp on the dash comes from a sensor in the drivers side head. What the VCM sees for engine temp comes from the ECT sensor which is close to the t-stat housing.

[sloppydawg123]

There was a cut wire in one of the o2 lines, reconnected the wire, cleared the codes, fuel loop closed as they should. Thanks for the replies

[j cAT]

Originally Posted by sloppydawg123

There was a cut wire in one of the o2 lines, reconnected the wire, cleared the codes, fuel loop closed as they should. Thanks for the replies

I would replace the O2 SENSOR slicing these wires causes problems with proper engine performance..

[sloppydawg123]

well, the cut was in the wiring harness side of things, not the wires off the sensor, so for now i'll just see how it runs and proceed from there