Multiple misfires, rough running

Well the temps have dropped off here considerably. It was the last day of driving the XK8 for work for the year. Temperature was low 20’s Fahrenheit. I had made 4 stops all close within 2 miles of home, so the car didn’t have time to warm up fully, but was running good like normal. I haven’t been driving it quite as much lately either, but did fill up with premium fuel at the usual station about a week ago, and had driven out about 1/8-1/4 of the tank already (honestly I normally run regular unleaded, but put in premium this time).

As I’m pulling up to a stop light the check engine light starts to blink as the car audibly sounds like it is misfiring (kind of sounds like a muffled, repetitious thud from inside the exhaust, almost like there was an exhaust leak upstream of the muffler). You could also feel the engine shake more through the steering column and it felt like the torque converter didn’t know whether to grab or let go, making the car mildly jerky especially at slow speed riding the brakes.

Before I had a chance to pull over the check engine light went off, but the car still ran the same. I drove it about 1/2 mile more and parked it. When I got out I noticed the smell of fireworks coming from the car (sulfur?). While idling I popped the hood to see if I could detect the smell from under the hood, as I suspected an exhaust leak upstream of the catalytic converter, giving the O2 sensor a misreading. No smell under the hood, but strong from the tail pipes, I believe primarily from the right one. No oil/water leaks underneath. Stopped the engine and let it sit for 20-30 minutes.

Started it back up and this time the check engine light stayed on solid. I limped it home (2 miles) and it ran like it was misfiring. I drove gently and only drove up to 35mph, with the same sound and feel as before. Shut it off and the fireworks smell was still strong out of the tailpipe.

Recent work done in the last 6,000 miles includes new fuel pump and fuel filter, MAF hose (PO purchased, do not know if MAF sensor was replaced but it looks clean), and regular maintenance like air filter and oil change.

I plugged in the reader and came up with the following relevant codes:

P0300-Random misfire detected
P0303-Cylinder 3 misfire
P0306-Cylinder 6 misfire
P0307-Cylinder 7 misfire
P1313-Misfire rate catalyst damage bank 1
P1316-Misfire rate excess emissions

I cleared the codes and reran the car at idle with no more check engine light or codes thrown, but still running rough.


I had previously purchased spark plugs, so I went a head and installed those today to check that off the list as they were due at 100,000 miles (car is currently at 106,000 miles). The spark plugs were pretty straight forward and easy on this car. I replaced with what came out, which were NGK Laser Iridium IFR5N10, and gapped to .037-.038. I’m no spark plug guru, but they appeared pretty fouled...I think they were originals so had been in for a long time. The spark plug holes in the head were pretty clean with no oil or water ingress. I swapped the original Denso branded ignition coils, keeping them in the same bank but reversing the order to see if the misfires would follow...they did not. I visually inspected the ignition wires and they looked fine. I cleaned the ignition plugs with non contact electrical cleaner. I also degreased the PCV valve. It seems like on these cars it is difficult to tell if it is working, as air typically blows through both ways, so it is still a possible on the list.

After reassembling it all, connecting the code reader and clearing codes, I started the car and it still ran rough and immediately threw a solid check engine light. The following codes were retrieved:

P0300-Random misfire detected
P0301-Cylinder 1 misfire
P0306-Cylinder 6 misfire
P0307-Cylinder 7 misfire
P0316-Misfire rate excess emissions

Remember I swapped coils, but the misfires did not follow. Jaguar branded battery looks like it is 4 years old. I’m thinking it could also be a bad tank of gas, but I did drive it a bit on this tank already with no problems. It is so random I could almost believe it is a low battery, but I didn’t think it could make it run so rough...but if it is not getting the spark it needs I suppose it could be.

Next up on the list (not exactly in order):

Load test the battery, it may still be too low from the cold weather and the multiple stops I make. It is on the charger at the moment (6+ hours and still charging, might be a sign), but upon testing it may need a new one regardless.

Possibly change the PCV valve for a new one.

Change some or all of the ignition coils as they are probably near the end of their service life.

Read fuel trims (this would be new to me so I’d need to read up on what to look for).

Dump a can of BG44K fuel system cleaner in the gas tank to clean the injectors.

Check for vacuum leaks.

Check grounding points on car.

Some of these ideas I’m pulling from the searches I’ve done on the forum with members who resolved similar issues.

I thought I’d start this thread to document what I find and hopefully help others with similar issues down the road.

(Note pictures of spark plugs and coils in order are with the top of the picture being the front of the car.)

Anything else obvious I may be missing? Anyone have something similar happen?

 

You're suspecting the right kinds of things.

Any oil/damp/dirt in the plug wells can cause trouble (by upsetting or damaging the coils).

 

I charged up the battery and restarted the car, but it was still running rough. I then pulled the battery out of our XJ8 and it charged up quickly. I also pulled the PCV valve off the XJ8 and installed it with the other battery onto the XK8. I started it back up and it still logged the following codes:

P0301-Cylinder 1 misfire
P1316-Misfire rate excess emissions

It’s interesting the other misfires went away but is still just logging one now. I honestly think there may be several things coming into play here as the car ages and parts wear. I think the battery is weakening as I put it back on the charger and it is taking a bit to charge again, despite just sitting overnight on it. The PCV valve may have been on it’s way out, too. The swapped one was definitely cleaner inside. I still suspect there may be some coils on their way out, too. Fuel rail prssure reads 55psi. I reread the codes several times with different ignition cycles and cylinder 1 is the only one that is misfiring.

I plugged the scanner back in and looked up short term fuel trims and downstream fuel trims. As the engine was still cold (trims were retrieved in under one minute run time) it was running on open loop. It is interesting bank 1, where most of the misfires have come from and where the catylist damage triggered, reads anywhere from double to triple what bank 2 reads. What this means I am not too sure. Is there some fuel pressure regulator for each bank? It could be an injector clogged or going bad. Perhaps a sensor went kaput. It sounds like a vacuum leak is probable due to the fuel mixture being enriched.

 

My guess is a very recent air leak on bank 1 (passenger side). Your short term trims are super high.

Check the VVT seals for oil leaks (likely means air in), all the lines to the heads and the throttle body (most are squeeze and pull and take o-rings). Check the oil dip stick o-ring, too. Check the big air intake pipe, especially at the bottom.

Best of luck, keep us posted.

 

First thing I thought of was an intake leak. There's lots of plastic parts that can crack over time and the heat they are exposed to. The crack may be hard to see.

 

Thanks for the replies so far, guys. Looks like I may need to rig up a smoker to check for air leaks. I’ll visually inspect them again, too.

I pulled the dipstick and sure enough, no O ring. I swapped it for one out of the XJ for the time being while I’m testing things. I really do think this is a case of the straw that broke the camel’s back...I think there are enough small things that multiplied and caused a bigger problem.

I cleared codes again and reran the car through a couple of idle cycles. Couldn’t get the CEL to come on again but it is still running “lumpy” so it’s just a matter of time, and the fuel trim on bank 1 is still high. I do think after the PCV and oil dipstick change that it does not run quite as rough, but it is still bad enough I wouldn’t dare drive it. She’s parked until I get this sorted. At least it’s cold enough I wouldn’t be driving with the top down anyways.

 

I would clean the MAF for the 5 minutes it takes, I don't think mine had ever been cleaned and it was really dirty, stumbled and backfired when cold. now it clean and smooth. check your air filter too.....

 

Are you sure you put in premium gasoline and not diesel?

 

Yes, they don’t offer diesel at the pumps there.

I did find this thread in the general section, which I am finding extremely useful. Being a beginner in fuel trim reading, it explained it at my level (two PDF documents are in the thread). I was curious as to whether failing ignition coils would produce high fuel trims, and this document verified that it is indeed what happens. It also shows what effect a small air leak, such as a missing gasket on a dipstick, can produce. I didn’t realize it had such a drastic effect. I’ll leave it here for anyone else interested:

https://www.jaguarforums.com/forum/g...ed-quiz-49317/

I am certain I have air leaks (like no dipstick O ring). I am guessing the coil packs need replaced, too. I believe the PCV valve swap cleared the other random misfire codes, now I can only get cylinder 1 to misfire on a regular basis. I am putting a parts list together, including VVT seals.

I don’t believe the MAF is the primary suspect on bank 1, as it should effect both banks equally, though a cleaning certainly wouldn’t hurt. Air filter is clean.

 

Its not just an unmetered air leak that gives high fuel trims, a misfire on one or more cylinders gives the same result and as the high trim is on one side only, the misfire is the more likely culprit. Sort your misfire out on cylinder 1

 

I have mentioned this before, but the easy way to get to those air leaks is to get one of those o-ring kits from a place like Harbor Freight, and casually, one at a time, replace all the o-rings you come across around the throttle body and cylinder heads. As you go around, one hose at a time, you can typically see the short term trims go negative, and, over time, see the long term trims go lower and lower. Target is to have them be below, say, 5%. In my experience with my car, anything over, say, 12% is noticeable while driving (lower throttle response, pinging, etc) even if no code is triggered.

Also, as you have the later car, the AFM can be found for real cheap. You need a Denso 197-6030.

Best of luck, keep us posted.

 

Thank you for all the helpful replies!

I received my ignition coils today and installed 4 new coils on bank 1, and kept the stock Denso coils in bank 2. Ran a couple of ignition cycles and no DTC’s, it idles much smoother, and fuel trims on both banks are close to matching and very low.

I ordered an O ring kit from Amazon and am still waiting on my dielectric grease, VVT seals, etc, so I am not ready to put it back together and check for leaks just yet, but I am pleased the misfires are gone and fuel trims are close to matching!

On a side note, another forum member had purchased the Airtex/Wells 5C1420 ignition coils from Rock Auto and said his were FoMoCo stamped. I bought my 5C1420’s from them and no FoMoCo stamps, so we’ll see how they hold up! The price was certainly good, though.

 

I was going to suggest the dip stick but someone beat me too it.

The other thing I suggest you do is get some carb cleaner. With the engine running go around the plastic pipes. If your in the USA especially around the drivers side ones. Spray a little to see if the car tone changes. If it does you have found a cracked pipe sucking in the cleaner.

I had a cracked pipe. Got all sorts of warnings.

This is my story on that. If you cannot see any pictures if you look at the foot of the page you will see a link to a Photobucket fix. http://www.jaguarforum.com/showthrea...l=1#post941769

Hope it helps.

 

 

Good hint zray. Please visit the new member area and introduce yourself.

https://www.jaguarforums.com/forum/n...-intro-must-5/

To all, my 06 had high fuel trims, +10. Thr intake tube was the culprit, but the leaks were in the top of the accordian, not the bottom.

 

'fuel trims on both banks are close to matching and very low.'

So if the data is telling you you have no air leaks then why are you still searching for some? If it aint broken dont try to fix it works for me.

 

That is when that intake tube is not installed correctly, sits too high and rubs on the hood liner. Remember, the engine shakes on its mounts, so that intake tube is being "sanded" by the liner as the car is being operated. The trick is to double check the angle of the intake tube on the throttle body. Only tighten the clamp as the tube is pushed down a bit to make sure there is no contact with the hood liner.