3.0 didn't stumble...it FELL

[beaterranger]

So cruise is set at 75 on my 91, life is sailing along perfect. Water is good, oil pressure good, no missing or hesitation. Then bump, cruise kicks out...on level interstate Half a tank of fuel showing, 165 miles into the excursion, fuel filter less than 10k old, mass air cleaned a month ago, IAC less than 3k old along with both temp sensors, egr deleted so that's out, hello curveball. Searched all over the forum but most of the similar cases seem to be accompanied with no start/stalling issue. So here we go with yet another stumbling/falling mystery of the 3.0: Sudden loss of power, no CEL, engine NEVER DIED, held steady idle at 1000 (which to me is higher than the usual warm op IAC idle of 700), starts and holds idle on time every time but pops/sputters the second you try to feather any throttle. Specs: 5spd, 3.0, 370k, new electrics (coolant temp sender, coolant temp switch, air temp sensor, TPS, IAC, ICM, Cap, Rotor, Wires, Plugs). The MAF,MAP,O2,EEC, and fuel pump/regulator have yet to be replaced. I still have several tests to conduct but the disconnect IAC KOER passed, wiggle test on sensors passed, tap test on MAP passed, no glow cat. At idle, smells rich but no black smoke, no fuel in oil. If anyone has a general direction based on the described dilemma, please share your thoughts. With no codes, I'm afraid this could snowball into replacing a lot of otherwise good parts hoping to "accidently" fix the problem.

 

[beaterranger]

Update 1: After cold start, 1500rpm steady til warm, fell back to 800rpm looks like IAC is opening correctly. Stumbled when trying to give gas in neutral BUT if I slowly feather throttle to 2000rpm and hold, about 30 seconds later the engine runs itself up to 3200+ at the same throttle position as if something somewhere is either supplying more air all of the sudden or more fuel. Rich smell goes away. Let it fall back to idle, and truck resumes normal driving with the exception of bogging when more throttle is initially applied and a noticeable miss as you're driving. 5 min of driving later, engine derates back to limp state and severe bogging, hesitation, miss...top speed in limp=7mph. Still no codes. Any advice would be greatly appreciated.

 

[SenorNoob]

If you hadn't already replaced it, and it were my truck I'd be wondering about the TPS. It's the likely the first part to respond when the throttle is pressed. (That is why it's there isn't it?)

After reading the whole thing best I can come up with is maybe one of the major connection points in your wiring harness has a bad connection. Or a ground.

No codes or the just the all clear code?

 

[Trfsrfr]

370k is impressive. I hope mine last that long.
Not sure if you have a distributor or not, but you may want to check out my prior posts.
I just got done finding and fixing the broken pick-up coil in my distributor. The magnet inside came loose and would cause many of the symptoms you appear to be having...
You couldn't see it until you had the distributor upside-down in your hands.