Trouble with coil module?

91 Olds 98 started running rough, 1st place i checked was the coil put my timing light on each wire just to see if I had spark, I was right the middle coil was not putting out any spark at all each coil ohmed out at 11. Replaced the coil & still the same problem. I will be looking at the ignition module this weekend, does anyone know if the module can be tested? If so how? Auto zone says thay cant test it. My next spot to look at is a short in the Ignition Module harness. I will touch each wire in the harness and to ground to see if I get continuity. Any other ideas will be appreciated.

Thanks
rbm11761

91 Olds 98 started running rough, 1st place i checked was the coil put my timing light on each wire just to see if I had spark, I was right the middle coil was not putting out any spark at all each coil ohmed out at 11. Replaced the coil & still the same problem. I will be looking at the ignition module this weekend, does anyone know if the module can be tested? If so how? Auto zone says thay cant test it. My next spot to look at is a short in the Ignition Module harness. I will touch each wire in the harness and to ground to see if I get continuity. Any other ideas will be appreciated.

Thanks
rbm11761

Welcome to AF.

Your post has been moved to its own thread since the thread you posted in was too old.

Before you check each wire in the ICM harness to ground make sure the ICM connector is open (disconnected from ICM) and any connectors on the opposing ends like at the ECU module and the crank position sensor, etc. are disconnected. Otherwise you may get a false short to ground or a short indication that is normal. I hope you are using a wiring diagram of the ignition control circuits?

Thanks Bnaylor, I just opened my OEM service manual and found the wiring diag (C-4-1) of the ICM. The question I now have is 1 pnk/blk wire is feeding all 3 coils if I had a ground in that wire (harness from connector-back) wouldnt all 3 of my coils be dead and not just the 1 in the center? Coil is brand new no spark from center coil, Old coil no spark from center coil. There are 6 leads between the coil & ICM 3 blu & 3 a color/blk. I'm starting to wonder now if I have an open in the center coil wiring from coil to ICM blu & grn/blk wire. Car runs idles ok but you can hear a miss, acceleration is poor, it dosent idle as bad as I would think for only running on 4 cyl.


Thanks
rbm11761

Hi All,

Just got the 91 olds running perfect again, I decided to go ahead and put a new ignition control module in I have only owned this car for 2 years I dont know when it was replaced last so I put the new module in an the Olds is up and running again, the control module was the problem.

Thanks :cheers:
rbm11761