Hey Brian, ... it would really help to get your codes read. Obviously, with your engine running rough, a 301 or 304 code will be set for the cylinders that are mis-firing. But there could other codes that could lead to a cause.
Rich or lean codes could lead to engine mechanical or vacuum leaks.
Also, I have seen plugged exhaust systems, namely the converter, cause this. Removing the 0-2 sensor and checking for exhaust system back pressure could verify an exhaust system issue.
You might want to make sure of the basics first by taking an engine compression test. Make sure the engine is good. You have replaced your spark plugs, but you're right in thinking, "am I getting spark" to the spark plugs. It is kinda tricky trying to check for spark to the plugs with your coil pak.
We have test spark plug wires that we attach between the housing and the plugs. Then we can check for spark to the cylinders.
One of the biggest failure components of the engine and ignition system is the ignition control module. The module is the part in the picture below.
This is an expensive part and if you should guess at the repair and just replace it, this part is not returnable as it is an electronic part. So you'll want to be sure of your diagnostics.
I have included a Word Doc. that has a flow type chart for diagnostics on an engine misfire. It does call for some special tools and it doesn't mention the possibility of a plugged exhaust system. This is something I have learned from experience.
Look it over as it might give you some ideas. There also will be some blue hyper links with-in the document. They are for my use and you will not be directed to any additional info.
Most likely you have a coil pak issue or the control module. But you should check things out before making the investment in parts, as it can be expensive. CLICK HERE
for word doc. on the mis-fire codes of 301 and 304.
Ignition Control Module (ICM) and Ignition Coils
|(1)||Ignition Control Module (ICM)|
|(2)||Compression Sense Ignition (CSI) Pickup|
|(4)||2-3 Coil Control|
|(6)||1-4 Coil Control|
The powertrain control module (PCM) supplies a signal on each of the ignition control (IC) timing control circuits to the ignition control module (ICM). The ICM fires the correct ignition coil at the correct time based on the signals. The ICM detects if cylinder 1 or cylinder 3 is on the compression stroke by sensing the secondary voltage and polarity of each side of the ignition coil.
The ICM detects this voltage with sensing circuitry integrated into each ignition coil. The higher voltage is on the compressing cylinder. This is called compression sense ignition. The ICM provides a synthesized cam signal to the PCM based on these inputs. The PCM uses the cam signal to synchronize fuel injection. This system consists of the following circuits:
| • ||An ignition voltage circuit|
| • ||A camshaft position (CMP) sensor signal circuit|
| • ||An IC timing control circuit for cylinders #1 and #4|
| • ||An IC timing control B circuit for cylinders #2 and #3|