I have a 97' F-350 with a 5.8 & it is about to drive me nuts. It will start & run fine until it warms up & then the engine light comes on & will start running rough at about 55-60 MPH. It is sending a 212 code with says ignition tach signal was eratic. Anyone have a suggestion on this issue? Where to start looking, or troubleshooting ideas? Thanks

 

Tfi module or distributor pickup
Hopefully someone else will give an opinion also

 

Is that the only code it has?

I agree that it sounds like the distributor or maybe the coil.

 

The IDM signal comes from the Ignition Control Module (ICM). Most likely causes are the ICM itself or the stator (aka PIP) inside the distributor. Highly unlikely the coil is the root cause. The ICM can be removed and tested at many auto parts stores. The PIP is difficult to change since it is located inside the distributor.

What color is the ICM? It should be black (CCD style ignition). It is located on a heat sink on the driver side inner fender near the hood hinge. The black ones rarely go bad, it's usually the PIP that causes the issue you described.

 

My bad, I was thinking of my old carbed motor where the tach plugged into the coil.

 

The ICM is Grey. We have tried 2 different ones & get the same results. I have looked into the PIP & it is almost as cheap & easy to change the entire distributor. I think that will be the next step.

 

The entire dizzy runs about $100 now with cap and rotor. I'd say just change the whole thing out.

 

The code you are getting is most likely caused by the gray ICM, you need a black one. Many of the part manuals are incorrect (even Ford!). The IDM circuit is completely different for a CCD style ignition versus a Push Start version. The IDM signal is generated by the ICM as an output on Pin 4 with the CCD style ignition. On a Push Start, the IDM signal is a function of the signal to fire the coil then buffered through a 22k ohm resistor. By using the gray Push Start ICM the PCM will never see the IDM signal which in turn triggers the error code.

The rough running is more than likely caused by a bad PIP, very common problem. Be very careful when replacing the distributor. Many of the so-called "rebuilt" units were never tested through a heat cycle. They are known to have a bad PIP in them right out of the box.

 

Ok, so where do I get one of the black ICM's at? I put a new distributor in & it is still doing the same thing. The truck runs fine until you are running down the road & then it starts pinging real bad & choking on itself. I am starting to get just a little frustrated at this. Thank god it hasn't snowed enough to really need the truck.