Fluctuating idle + stalling+ surging

[Mattybilt]

Ok well I just got home from a fun ride to the parts store! So far I've only put a little over 200 mi on my 95, it's just over 157k now. It was parked for almost 4 years so working out bugs but this is new.

 

A couple days ago it was idling high when I pulled up to the house, I put it in park and revved it up a bit and it lurched backwards a bit?

 

Today went to pick up steering hose for it and at 2nd red light it starts surging/idling up and down from almost 0 to 1100 rpm and blowing black smoke. It drives fine revvs fine above idle when I get going again. Got stuck at another light it stalls completely, but fires right back up. Pull into gas station put 5 gal in and fire back up and it's idling at maybe 2/300 chugging blowing black smoke again. Made it to store, left again train coming didn't want to wait so hopped on highway ran 2 miles at 65 no problem. Got stuck at 2 more red lights and it idled normal around 800 no issues! So now I'm perplexed.

 

Seems like it's running rich at idle suddenly.

Temp gauge only ever reads at 1/4 sweep max so does it think it's running cold?

Think I have a blown flange gasket on drivers side exhaust possibly throwing off the o2 sensor.

 

Fun times, no cel on either oh well figured I'd post to help others like similar posts. Any input it appreciated and will post my findings.

[Cuong Nguyen]

Faulty ground or plug for the MAF or bad O2 sensor or both. Give the plug a wiggle while it's running and see if you can replicate it.

[Mattybilt]

Well I think I got it, vacuum line from back of manifold to the fuel pressure regulator? Fell off on the rough road. Replaced it and it's idling smooth and running good again.

[RF600]

If you haven't already, add an extra ground to the maf.