Hey there, I'm roughly new here and just a while back ago my VDP had steering pump issues which fixed itself which I though was odd then one day I got the check engine light, went to get the codes pulled and its was an O2 sensor that went wrong. Ill be honest, I passed it over saying I'll take care of it later and the car was running perfect. Then weeks pass by and one morning when I started it, it had a shakey idle then restricted performance came on along with a flashing CEL. While it was on I took it to get the codes pulled and these are what I got...
#1: P0308 - Cylinder 8 Misfire
#2: P1314 - Misfire Catalyst Damage Bank 2
#3: P1316 - Misfire Rate exceeds Emissions
#4/5: P0358 - Ignition Coil H Primary Secondary Circuit (I got this code twice)
#6: P1646 - Linear O2 Sensor Control Banks 1&2 (I also got this code twice)
#8: P1000 - OBD Systems Readiness Test Not Complete
Ok so these were all the 8 codes it had. How does this happen from being perfectly fine to ALL THIS?? Please help me out, maybe some pointers to where I need to look maybe? I wanna do this DIY but if you guys say otherwise I'll take it in and see where we go from there!
Thank you, cat4su

 

Well, I would start by looking into the cylinder 8 misfire! That is the cylinder at the rear of the left bank (driver's side for us!). Remove the coil cover, remove the #7 and number 8 coils. Examine the #8 coil for signs of arcing. Check the plugs while you are there- note any differences in appearance between the two. Swap the two coils, reassemble, reset the codes and drive to see if the fault moves to cylinder 7.
Then we decide the next step.

 

Ok so I did it but instead of #7 I did #6 and then these codes popped up some new some repeated
P0300
P0308
P1314
P1316
P0358
P1646
P0308
P1316
P0357
P1000
P1384
P1646
😩

 

OK, what is the year model? I ask this because the AJ26 and Aj27 engines have different ignition primary circuits.
Did you reset the codes after the swap?
BTW, you do know that your secondary tensioners have been replaced, right?

 

I also forgot to mention that there was oil and gunk around the bottom of both ignition coils

 

If you have an AJ26 engine AND you reset the codes,the next step would be to swap the ignition amplifiers located in the plastic "box" in front of the brake booster.

 

It's the 1999-2000 model year and yes I reset it after the swap

 

Oil can interfere with coil function. Change gaskets so no more oil and any damaged coils.

 

Clearly oil in the plug wells are causing issues. You will need to remove the coils and clean them.

Still, might be mistiming issue, as well. HAVE THE TENSIONERS BEEN RENEWED?

 

As JagV8 and Jim have noted, the oil is a very likely contributor to your issues. One possibility is that the oil in the wells may seep down along the threads, bake on and partially insulate the threads, increasing the resistance to ground/earth. The threads of the spark plugs mating with the threads in the cylinder head constitute the ignition circuit path to ground.

 

I am going to respectfully disagree on the likelihood of the oil soaked threads being the failure mechanism for oil in the wells. I THINK that it is more likely that contaminants in the oil shunt the high voltage side to ground. It would take a pretty high resistance to lose spark due to improper grounding, and there is certainly an interference fit, at least for a properly tightened plug.

So, since the engine is an AJ27, and has the ignition amplifiers integral to the coils, and the coil is swapped but still gives a code for cylinder 8, it seems like the actual coil is not the culprit. If the oil mess was not cleaned up, and the boots checked for burns or cracks, then that is still in the game.

BTW, I use a wet and dry vac, with a small tube taped into the large hose to fit over the plug and suck out the oil. I only do this with the car and vac outside the garage and, although it hS NOT HAPPENED YET, I fully expect that one time I do this the vacuum will blow up due to a combustible mixture igniting in the tank. So, if you are not adventurous like me, DON'T do that!

And I saw nowhere that the plugs were examined. While you are there, I think a compression test on cylinders 6, 7, and 8 is in order. Nad, no reply to the tensioner question. The fact that several of us have asked about that should indicate it is a real concern.

 

Ross,

I defer to your expertise. I raised the possibility of oil on the plug threads being an issue because on a friend's X300, replacing plugs with oil baked onto their threads in two cylinders solved his misfire problem (swapping coils around had made no difference). At least one of the coils showed some signs of arcing, and it was my presumption that the baked-on oil was interfering with the ground path through the plugs, so the arc was finding a lower-resistance path. I hadn't thought of contaminants in the oil (metal particles?) making the oil an attractive shunt, but I'm happy to accept it for lack of a better explanation. Of course, we had wicked the oil out of the wells before removing the plugs, so it's possible that alone was the solution to the problem.

Cheers,

Don

 

It is easy enough to test! Next time I encounter a fouled well, I will measure the resistance of the plug base to ground. If anyone has a chance to do that, it would be interseting to know!

 

I expect oil can't get far down the threads, else combustion gases could readily get out...

 

Proper spark plug torque is probably the answer, but it can't be taken for granted. And it doesn't take much of a passage for capillary action to draw in a liquid. If you google "Oil on spark plug threads" and then click "Images," you'll find hundreds of photos of spark plugs with oil on their threads. Here's just one example:





See what this mechanic finds when he pulls a plug. The wet oil no doubt gets on the threads in the process of unthreading the plug, but it's obvious that some oil is baked on after he wipes off the plug:



Cheers,

Don

 

Yeah, and those plugs clearly have not been firing right either! Hell, that plug has deposit on all of it. Maybe the deposit is coming up out of the engine?

I don't remember... Are Jag plugs compression ring sealed or tapered thread? Does that matter? In any case, there is clear evidence that plugs with an oily well many timse have misfires. What the exact mechanism for misfire is is less important.

 

I don't think the plugs are tapered - I think they're standard 14mm thread, and they do come with compression rings.

 

Spark plug torque won't always be correct but incorrect torque would not be high on my list of suspects for misfires.

Capillary is quite small, especially for oil, whereas combustion creates big pressures so most of any fouling is likely from the cylinders. Most plugs go on for a very long time without serious misfires despite both of these potential problems so their effects must be small/rare. I would not be looking at these effects on the plug threads as likely causes of misfires.

However, if the age/condition of the plugs is unknown/suspect I'd probably change them (and correctly torque of course).

Fouling of coils (COPs) commonly causes misfires it seems to me.

Another cause is a blocked cat.

 

+1 fouling of coils.

Still, not yet satisfied it is not a timing problem.