91 ranger random misfires

[Mikel89us]

These systems use one coil pack for low rpm, both for mid range, and the other for high RPM. Its normal for it to not start with one of them unplugged.

As we have with the Mustangs, the coil packs fail often, and the DIS modules fail almost as frequently. If you have the money to buy the DIS you should probably throw the little extra cash at it and get both coils and new plugs and wires. A full tune up would work wonders on it I'm sure.

 

[geowik]

Thanks for the help Mike. So from what you said I am taking that means that the power coming from the DCM to the coils cannot be checked with a test light for comparison to each?? Now that you say it is normal for only one coil pack producing spark at idle does that also mean it will not be receiving power from DCM at idle?? I am wondering if the coil pack or DCM may be the problem or not as it runs bad at idle and all RPM's. I am planning to change all plugs and wires as $$ permits but for now I think maybe I will start with pulling off the DCM and having it checked out. Thanks again for your help

 

[geowik]

Interpret codes??

Can someone please help me in interpreting these codes or offer suggestions??

DTC:96 - fuel pump secondary circuit fault/high speed fuel pump relay open

DTC:18 - #1 loss of tachometer input/IDM circuit failure/spout circuit grounded #2 spout circuit open or spark angle word (SAW) circuit failure

DTC:88 - (trucks only) choke relay out of range. Dual plug input control failure. shift solenoid 3/4 - 4/3
Doc!!

 

[adsm08]

So from what you said I am taking that means that the power coming from the DCM to the coils cannot be checked with a test light for comparison to each??

The way your ignitions system works, at the base of it, is not actually all that different from the old points/condenser systems.

The coils are always hot with the key on. The module acts like the points, breaking the ground side of the circuit at a particular point to collapse the field and fire the coil.

You can check the trigger signal with a dumb light by unplugging the coil pack and running the light from battery + to the trigger wire and cranking the engine. If it is getting the correct signal the light should flash.

You can also check the tach signal to the ICM by unplugging the module, placing a voltmeter set to read AC volts on the pins going to the crank sensor, and cranking. It should get close to 1V AC while cranking.

 

[geowik]

DTC:96 - fuel pump secondary circuit fault/high speed fuel pump relay open

DTC:18 - #1 loss of tachometer input/IDM circuit failure/spout circuit grounded #2 spout circuit open or spark angle word (SAW) circuit failure

DTC:88 - (trucks only) choke relay out of range. Dual plug input control failure. shift solenoid 3/4 - 4/3

I started out replacing the DIS module and got lucky. It is running great. As soon as money permits I will also be changing out the spark plugs and wires and eventually the coil packs.

Today I am replacing the fuel guage sending unit/fuel pump as the gas gauge does not work. I looks like the easiest way is to remove the truck bed.