2002 Intrepid

[donjuan8er]

I just bought my '02 Intrepid from a lien sale. I brought it in for a smog check. Emissions = pass, Functionality =P0354, ignition coil #4, high impedance,because of rough idling couldn't get the certificate. So I bought a new ignition coil and replaced spark plug, same rough idling took it to 2 shops, they performed a compression test and said that no. 4 cylinder has only 60 while the rest had 90 and above. I was arguuing with them, though I am not an expert, on why the mil code shows one thing and they are telling another. The windshield washer works, the wipers don't, the radio works but no audio, is there some kind of electrical issue affecting the idling too? I don't believe it's a cylinde head issue. What gives?

[mouse23]

I had a similar problem and this was my approach.
1. I swapped coil modules......... No results.
2. changed spark plugs to Bosch, .........problem got worse.(bigger gap)
3. Bought a current probe on Ebay and measured coil current at each coil, using scope to display. The current wave shape looks like a saw tooth, a ramp going up and the then dropping to zero instantly after about 1.5 msec. At that point the current has reached at least 4 amp.
The ramp on cyl#1 had a shorter duration so the current did not reach the same value. This makes the spark intermittent. When I made a smaller gap at the plug the problem disappeared. This is a stop gap fix. The problem is caused by the ECU (PCM). A reflash of the PCM at the dealer with the latest firmware may solve it ?
Myself, I fabricated a pulse stretcher for the coil in question, to give the current a little more rise time. This without interfering with the function to the PCM.