Module problems

[amtech4]

Here's the full situation. A couple of months ago my cat conv. became plugged and was subsequently replaced. Less than 2 weeks after replacing it, I got a check engine light and the engine started to run hard. I scanned it and got a #5 cylinder misfire. Okay, no problem. I checked the wire- it was good. I pulled the plug- some carbon build up so I replaced it. I cleared codes and started the vehicle and got the engine light again with a rough engine. Scanned it- #6 cylinder misfire. Checked wire- it was good. Checked plug- it was good. Resaeted all connections and cleared codes. Started vehicle and got the same thing. Scanned codes and got a #5 cylinder misfire. Back and forth I went with no joy. In the middle of this I also changed the cap and rotor just to eliminate them. I suspect a bad ignition module, am I right? But wait, there's more. Now, when I turn the ignition to on, I get minimal voltage read from the battery (fully charged off the charger) and after the vehicle starts running, for the first 5 seconds or so there are absolutely no indications on the gauge cluster and no interior lights. All the sudden everything comes online with all gauges functional. I suspect a bad ECM or BCM, am I right? Please help, I don't feel like paying a mechanic for something I can do myself.
I am working with a 98 Blazer with a V6 Vortec.

[BlazerLT]

Have you done a tuneup lately?

Don't just replace one plug, do a complete job.

[amtech4]

Matter of fact yes I have. About 3 months ago. That wouldn't explain the misfire bouncing back and forth between cyliders 5 and 6. I replaced all 6 plugs and all wires back then. What about the electrical problem, they aren't tied together. I am quite frankly at my wits end.

[blazes9395]

I would say the electrical problem could verywell cause a problem like this, by not provide stable or proper voltage to the PCM, and in turn not providing proper voltage to the injectors. I would be trying to figure the electrical problem first.

Try putting a voltmeter on the battery, start it up(or get someone to start it) while you are watching the meter and see what readings you get, it should just after you start it, begin to reach approx 14 volts, indicating your alternator is working. If its slow to reach that output, then take a look at the charging system.

[BlazerLT]

Originally Posted by amtech4

Matter of fact yes I have. About 3 months ago. That wouldn't explain the misfire bouncing back and forth between cyliders 5 and 6. I replaced all 6 plugs and all wires back then. What about the electrical problem, they aren't tied together. I am quite frankly at my wits end.

Cap and rotor replaced?

[Extreme28]

You may want to look for a short in the electrical. I would also consider checking the ignition switch. I had a simular issue on my 96 and it turned out to be a wire on the colum shorted out.