Ongoing idle surge issue Fj62 (2 Viewers)

[blainehale]

Howdy folks,
1989 Fj62 with the stock 3FE motor. Only modification is removal of smog gear.
For years now I've had a pretty bad idle stutter/surge. Once the truck warms up it immediately starts acting like it's losing a cylinder, or something, and stuttering the idle. Off idle, it's perfect...no issues. I de-smoged it years ago and don't remember if it aligned with when the issue started but I'm pretty sure they were not at the same time period.
Things I've done:
-Rebuild and replace the sensors in the thermostat housing like cold start and temp sensors
-Replace all vacuum lines with silicone and tested for leaks with one of those vape things
-Recently pulled the injectors and had them rebuilt...I thought this would be the issue, NOPE
-Inspected and cleaned the idle air control unit
-Noticed almost all my spark cable boots were chewed off by a rat so I replaced all cables

Going a bit crazy hunting this issue down. Anyone have any ideas? I have an OEM fuel filter coming since it probably needs replacing anyway. I can't seem to find any chewed up wires or vacuum lines.

 

[SteveH]

Replace oxygen sensor? Is EGR or block-off plate well sealed?

 

[blainehale]

Replace oxygen sensor? Is EGR or block-off plate well sealed?

EGR has the recommended cap on it and doesn't show signs of leaks, same with the block-off plate which has the gasket as well but I could go back and permatex that.
Hadn't thought of a o2 sensor so I'll order one. I wonder if that would be why I also seem to be running rich.

 

[SteveH]

Often, bad O2 sensors cause 'hunting' at idle. You won't likely get a code if it's bad on an FJ62, either. Try Rock Auto for a Denso at a reasonable price.

More Information for DENSO 2344056

 

[zeeklafreek]

I don't have a dog in this hunt (running a stock 2FE) but now, whenever anyone has any issue with idling or stalling with a 3FE or a Holley Sniper, Imma just gonna tell them to check the O2 sensor.

 

[blainehale]

Update: I was able to replace the o2 sensor for the front bank of cylinders after some struggle. It did not resolve the issue. I've got another sensor for the rear bank but that's going to be even more of a struggle to replace as someone has welded the exhaust down pipe to the cat.
The struggle: My o2 sensors have the little guard on them so it's impossible to get a wrench up in there and even if I could, they're the factory nuts/studs so it's all seized. I used an inductive heater to break free the down pipe and pulled it out. From there, more inductive heat on the o2 sensor nuts, at which both studs immediately snapped getting the nuts off. Even with more heat, vice grips and even welding nuts to what was left of the studs...they would not free. Screw it, new down pipe was $100 and worth me not having to drill and tap the studs.

 

[AndersBror]

I know this sounds simple but have you checked PCV and vacuum hoses?

 

[White Stripe]

Pull the throttle body, strip it down, and clean it up. Check the dash pot and idle screw. Make sure it's adjusted right. Check to see if you have a good tps and iac.

 

[toy_tek]

test fuel pressure and agree on checking/cleaning/adjusting TPS.