IDLE drop at open loop then looping

[golddigger]

I have a 88 4.0 which runs pretty good except when initial startup when it goes into open loop then idle will drop way down stumble back up then start to surge slightly 

any suggestions what i could be missing 

 

John    

[Ωhm]

With ENGINE RUNNING, check for Battery Voltage on D2_9 (O2 Heater Circuit).

 

 

[golddigger]

thank you  OHM   what should i be seeing on a good circuit?  

John

[Ωhm]

10 hours ago, golddigger said:

what should i be seeing on a good circuit?  

Battery Voltage with ENGINE RUNNING. This is a quick test. If GOOD, need to check O2S heater on the component itself.

 

 

Disconnect C229 and on the component side connector check for resistance between pins C229_A and C229_B. Looking for ≈6 Ω's. If TRUE, circuit is GOOD.

Note: This view is harness side.

[87MJTIM]

I'll throw my 2¢ in - have you checked for vacuum leaks?

 

Mine was idling rough - 800 down to 500 rpms - with STFT down to 0. It felt like it would cut out at any second.  I had a cracked vacuum line from the MAP to the TB.  Fixed this and the idle is better.  However, STFT is still low - 30-50.