I have a 92 Extra Cab 5.2 with 148k miles. 10k miles ago I had a terrible idle and stalling problem. Now I have no codes. It starts easy. It idles well. It drives good. It just doesn't have the power I had before and my mileage on the interstate has dropped from 21+ to 17. I can't spin the tires even if I try to power brake it. I know, I know 92 model blah blah blah. I'm not trying to drift this thing all over town. I have lost confidence in it to pass on the rural roads I live on. It takes a bit longer for it to drop out of OD when passing. When it does it is slower to build speed. I hate to mess with it because, as I said, it is running pretty good. A different driver may not even notice the power loss and think it is just a bit lethargic because of age. Before the idle issue the thing was tricky in the rain. If I hit it a little too hard from a stop, especially turning it would fish tail.
Below are the items I replaced addressing the earlier issues and some regular maintenance.
-TPS also set initial voltage to .7, .8, and .95 WOT is 3.9-4.2. Absolutely no lag or hesitation.
-AIC/IAC depends on who you talk to
-MAP and rubber elbow
-Removed and Cleaned the TB used new gasket
-coolant temperature sensor
-Air Charge temperature sensor
-plugs, wires, distributor cap and rotor
-ignition coil
-PCV
-transmission filter and fluid
-Fuel filter
-Tensioner pulley
-oil and filter
-air filter
-battery
-complete front end rebuild
Any ideas? I want that zippy feeling back. Thanks for any help.

 

Check the exhaust for constriction.

 

Funny you should mention that... The cat and the muffler were next on my list along with verifying the brakes aren't dragging them. I've had dragging brakes on a different vehicle before and it doesn't feel like that. Thanks for the confirmation.

 

The intake manifolds on those are two-piece as well, and the gasket is notorious for blowing out, which throws off the map sensor, so, the engine doesn't run as good as it should. (also fouls plugs, and clogs cats.... burns oil, etc.) Pull the air hat off the throttle body, crank the throttle wide open, (engine off.) shine a bright light down there. See oil pooling? Plenum is blown, and ya need to address it.

 

Nice. Thanks for some direction. Plugs are good. It uses less than a quart every three to five thousand miles. I'll check out the intake. I wasn't thinking in that direction because it runs so stinking good it's just low on power.

 

I opened up the TB this morning and took a look with a flashlight. The aluminum is stained but no pooling oil. It barely appear damp. I couldn't say for sure it was.I kn ow with recycling through the PCV and the vent in the breather the inside of the intake could be discolored. I've never seen one on any car that wasn't. That wasn't conclusive. I'm not saying that isn't the problem. I'm saying it wasn't clear by looking. Here are a couple of shots of each side. I took about 100. These are the closest to what I saw with my own eyes. Flashlight and camera wizardry darkened the bottom a bit in the others. The last one (smaller opening) was after running the motor until warm. What do y'all think? Anybody had this issue with similar looking intake internals?

 

That thing is covered in baked on oil. It should be clean steel or aluminum, if it has had a Hughes plate put in. If it were me I'd want to find out why it is covered in baked on oil.
Maybe remove the TB again and get a better look down there? That said IDK that this would be the source of your sudden onset problem, but surely that is causing some kind of effect. And it looks wet to me.

 

Thanks for the input. I was just wishful thinking. This is my only ride right now but more importantly I just don't want to have to pull the intake. Lazy? No, I say busy. I better get unbusy or I'll be walking.

 

Yeah, pull the throttle body, and have a look at the back of the intake. I would be that you find oil back there.... Also gives you a better look at the pan.

 

I tossed in the towel and bought the parts. From what I've read it is an inevitability. It will fail if it hasn't yet. At 148k it is more likely than not. I got the Dorman kit (615-310) and an aluminum plenum plate from a source on ebay. It appears to be a solid unit. I like to line up all the tools and the parts before I start. I am a Rural Rodscaper. That means I have no building to work in so I'll need good weather for a couple of days. I don't like to rush through. Since I am this deep into it I will want ot look around at anything else I need to replace while I'm at it. I was hoping to find a used intake pretty cheap so I could just have it cleaned and fixed and swap it out. Nothing out there right now. I still plan on checking the exhaust and cat for blockage.