As title says I have issues with restricted power coming in on my 99 XJ8.

A couple of months ago a local shop "specialized" in European cars replaced the spark plugs and coil # 1 based on error codes P0301 and others.

The car ran fine for a while and earlier this week while driving to the airport restricted power came back on. Upon returning from my trip it started fine and half way home the restricted power and check engine light came back on.

I checked the codes and this time I would like to try to fix it myself. I have following codes

P0305 P0305 Cylinder 5 Misfire Detected
P1314 Misfire Rate Catalyst Damage Fault - Bank 2
P1642 P1642 Fuel Pump Monitor Circuit High Input
P1316 P1316 Injector Circuit / IDM Codes Detected
P0355 Ignition Coil E Primary/Secondary Circuit Malfunction

Based on what I've been reading here, I've pulled coil # 5 which I believe is is the front left cylinder (seen from the drivers perspective). It all looks good and there's no oil in there. I pulled # 6 right next to it as well for comparison and I cannot tell a difference.

Am I heading in the right direction to replace this #5 coil and if so where is a good place to buy them reasonably priced here in the US?

 

last time i saw one of these scenarios, the coil wasn't the problem, as all coils on the previous member's car was replaced...and same CEL later on. Now, I'm not saying this applies to you, but the secondary circuit function error/code added to the list now makes me think the problem will lie in connectors, wiring, and worse yet...the ECU. Companies do provide rebuild services for these modules, so don't die of a heart attack yet.

If you swap all the coils around one its bank (just in case you don't know 100% that coil 5 is where you suspect it, then drive it. If it jumps to the other bank...its definitely electrical related, see the list above. If it stays on your bank, then it very well may another coil. I have heard of one coil's demise leading to the others, as it throws off the ignition sequence for long periods and contributes to another coil death. Is this coil 5 on the same bank as the previous replaced coil? (sorry, don't have my engine diagram for your car memorized)

 

Previous coil that was replaced was # 1 on bank 1. Coil # 5 is on bank 2 from what I can tell.

So if I understand this correctly, I should swap the coils around on bank 2 only?

 

OK so I swapped coil # 5 with # 6 (on the same bank 2). Drove all week to work no issues. Today drove to the mall and the CEL and restricted power came back on.

Following codes were read

P0306 Cylinder 6 Misfire Detected
P1314 Misfire Rate Catalyst Damage Fault - Bank 2
P1316 Injector Circuit / IDM Codes Detected
P0356 Ignition Coil F Primary/Secondary Circuit Malfunction

So does this confirm that the coil now in # 6 is bad or is there still the suspicion that the ECU could be at fault?

If the coil is bad, where's a good place to buy them?

 

Okay, I dragged this thread up because the same thing happened to me. I got a P0356 out of the blue yesterday. So I pulled the #6 coil and checked it out. No obvious issues. So I swapped it with #5 and of course, now the issue went away. I did take the boot off and stretch the little spring in there (hint from Max H. of Taz) and sprayed some electrical cleaner in there. I went ahead and ordered a spare used coil anyway. But now I'm wondering if the problem was just a bad connection between the spring and the spark plug, because this happened to me before and I did the same thing a few months ago - I didn't write down the previous coil, but I know it was either 5 or 6. Just wondering if anybody else has had similar experiences. Cheers.

 

Looks like the coil as the fault code is moving to the new location of the suspect coil. To doubly confirm this, move it across to the other bank of the engine & see if the fault code migrates to the other bank.