Did a search and did not really find any defenitive solutions.

94 Explorer 4.0 with 24X K miles. Just all the sudden it has begun to buck hard while driving down the road after it gets warm. It is doing much like the old duraspark modules when they die. The tach drops to 0 if it persists long enough. Initially, based on wifes description, I believed it to be fuel related and changed filter, pump relay, and fuse. The pump is fairly new and runs. It ran long enough to pump out all of the fuel the other day without hesitation.

Codes are 542 (pump power) and 211 I think.

Module?

 

542 for fuel pump may not be a big deal. I've gotten this in the past but could not attribute it to any issues and I never addressed it and never got the code again.

211 is a missing PIP signal which is a big deal. This is the signal from your ICM - ignition control module - back to the PCM - car computer - which tells the PCM where the engine is as far as ignition timing. The PCM then takes this signal and conditions it into a spark curve depending on what the engine is doing - accelerating under load or coasting to a stop...

So I could see a missing PIP signal raving havoc on ignition timing causing bucking as you describe. This could mean a new ICM - located directly in front of the battery - or damage to the wiring harness itself.

I do occasionaly get a bucking but more af a isolated miss. Driving along in a sustained speed and all of a sudden it kicks once. But only once. I look back to see if I ran over something but no. Really bissare. It happens once a year or 2. No codes. So I haven't persued it.

 

To circle the wagons on this thing:

The second code I got relates to the PIP signal coming from the crank position sensor. It controls both spark and fuel. I cleaned the front of the engine in preparation for swapping it when I noticed that the wire near the plug had bad insulation. It was soft and spongy and pulled off easily.

That conector is fairly common on Explorers and Aerostars of this era. There are 2 near the battery on Explorers with Shunts stuck in the end. The Aerostar's is in the harness between the hood hinges.

Problem solved

 

So the 211 code you got - is that the second one you are referring too or was there another after that?

Now the ICM located in front of the battery has 2 wires comming of it going into a single connector. I think the wires are pink. This connector is jumpered. This is the SPOUT signal back from the PCM into the ICM which then advances/retards coil timing. This is not the same as PIP. PIP is sent from the ICM to the PCM first, then SPOUT is generated and send back to the ICM. But maybe there is only one code for lack of SPOUT or lack of PIP. But either way, a missing jumper or a bad connection of one of the wires will not allow the coil toadvance and retard the curve correctly. You're stuck at 10 degrees (+4 from the octane jumper) at all times. This will make a motor perform really crappy.

So the second line you mention with a connector on it coming off the ICM - there is one more in the system sure, but I thought it was located near the DTC connectors. Mine is on my 93 Explorer. It is tee'd off the RPM signal line between the ICM and the PCM. It's purpose is to connect a tach. I guess Ford just wanted another point to hook up a tach for troubleshooting. This is just an open connector, no jumpers or anything, and just the one wire. Tan with yellow strip, right?