1996 Ford F150 4.9L - Used to start poorly when hot. Now barely runs

Asked by Rustbomb Jul 30, 2019 at 02:13 PM about the 1996 Ford F-150

Question type: Maintenance & Repair

Truck used to do (for several years) :
-Start a little hard when engine was cold, but after a few seconds run and
idle fine.
-Run pretty much ok, until shut off and you try to start it again before engine
has fully cooled.
-Then it would then be hard to to start, be very miss-y, have very little power.
After a little bit it would snap out of it and drive fine again.

Things I did over last few years to try to fix this:
-Replace plugs and wires
-Replace EGR valve
-Clean MAF sensor (engine code said MAF issue)
-Replace ignition control module
-Replace distributor, cap, and rotor.

What it has recently started to do:
-Starts a little hard when engine was cold, but after a few seconds idle fine.
can let idle indefinitely without sign of an issue.
-Barely accelerates and sometimes knocks and lurches when pressing the
-Maxes out @ 50mph but sometimes drops to maxing out @ 25
-Will snap in and out of it and seem to run ok for short bits.
-Engine temp will go up after while of this crappy running but I have
witnessed it go back to normal while still driving.

What I have done since this recent worsening of the issue.
-Replaced coolant temp sensor
-Flushed and replaced coolant/antifreeze
-Replaced MAF sensor.

Additional info:
-Not super high mileage ~125k  but it's a utility truck. It sits a lot. Sometimes
much longer that it should.
-It's getting very rusty underneath.
-Check Engine light has not gone out since replacing MAF. I know I need to
get it read again but I'm a little worried about driving it to the parts store.

2 Answers

Got the codes read - Cylinder 1 and 2 misfire - System too lean banks 1 and 2 - Crankshaft Position Sensor B circuit

Partially fixed - Replaced a bunch of vacuum hose pieces that looked ok but were crumbling. Truck runs *Much* better now but must have had a couple issues as the power still suddenly drops when doing a long acceleration like when getting on the highway.

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