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A few weeks ago, after about 10 minutes of normal operation/driving, the CEL came on at highway speed and the car started missing under very light acceleration. If not accelerating it ran as smooth as normal. CEL stayed on for the approximately 10 to 15 minutes it took to get the car back home.
Restarted it the following day, CEL did not come on. Drove it for 20 minutes and the CEL did not come back on but the miss persists, but now it requires heavier acceleration to make it miss. Perfectly fine at steady cruise and light/moderate acceleration. Have driven it a dozen times since and still no CEL, but still missing as above. Engine starts just fine, runs smooth, not over heating, no strange sounds at all.
Question - even though the CEL has remained off, was the code saved from when it did come on?
2013 Weistec 540/715 tuned CLS 550, 2008 E350, and '07 Jaguar S-Type R
Originally Posted by ss3964spd
A few weeks ago, after about 10 minutes of normal operation/driving, the CEL came on at highway speed and the car started missing under very light acceleration. If not accelerating it ran as smooth as normal. CEL stayed on for the approximately 10 to 15 minutes it took to get the car back home.
Restarted it the following day, CEL did not come on. Drove it for 20 minutes and the CEL did not come back on but the miss persists, but now it requires heavier acceleration to make it miss. Perfectly fine at steady cruise and light/moderate acceleration. Have driven it a dozen times since and still no CEL, but still missing as above. Engine starts just fine, runs smooth, not over heating, no strange sounds at all.
Question - even though the CEL has remained off, was the code saved from when it did come on?
Pretty sure it did store it. I'm no mechanic but it possibly sounds like a random misfire.
I actually have a code reader, an Innovate LM-2, that I bought years ago primarily to tune the A/F ratio on my classic car.
Hooked it up to the 550, it successfully connected to the CAN bus protocol, but there were zero DTC's stored. Hate to just start throwing parts at it. Car has only 45k miles on it but I'll start with the spark plugs.
Started out replacing the plugs with new OE Bosch. Started with #1 (front, passenger side). The spark plug wires/boots are part of the coil assembly, they cannot be separated/removed from the coil. The coils/boots are tough to get out without just yanking on the coil - which may cause stress/separation of the boot/wire from the coil. The boots have a hard plastic sheath. I used long needle nose pliers to reach down and grab ahold of the lip of the sheath and pull, which worked well. Toughest one on the passenger side is #4, the rear most. Also challenging is you cannot see or touch a single bit of the spark plug. Was concerned about cross-threading the new plugs so I used a short piece, maybe 12", of 3/8" rubber fuel line. The fuel line slips tightly over the spark plug ceramic insulator and allows you to change the angle a bit while turning it your hand until it threads in, then just pull the hose off and finish tightening with whatever assortment of rachet/extensions/flex joints/spark plug socket you need. The hose worked well.
On to the drivers side. Could see the drivers side rear (#8) was going to be a PITA, worse than #4, and it was. Removed the 2 bolts holding the coil body and, surprise, the coil body lifted right off but left the boot on the plug (clearly this was the reason for the engine miss) Some combination of heat and corrosion caused the spark plug wire connection at the coil to fail. The photos show he corrosion in the coil where the plug wire attaches, and the top of the wire/boot (still attached to the plug. The hard plastic sheath was brittle and basically just broke apart when grabbing the lip, I had to grab what was left of the body with the long needle nose plies which, thankfully, worked. Then used compressed air to blow out any bits before removing the old plug. Back to the parts store for a new coil. Rest of the drivers side went fine. I lined up all plugs, keeping track of where they came from, to compare color at the tips. #8 was slightly different from the others, further confirming #8 was mis-firing. Off to the parts store for a new coil, and the rest of the drivers side went fine, though still difficult due to lack of space.
Restart seemed ok, but upon driving started to miss again, even worse than before, and after a short time got a CEL and found a P0300 code, which is multiple mis-fires. Damn. Back in the garage, rechecked everything and cleared the code. another short time driving and again with the CEL, but this time gave a P0304 code, a mis-fire on #4. Cleared that, road test again, CEL again, P0304 again.
Cleared the code. Opened up the passenger side again. Swapped #4 and #1 coils. Back together, road test, P0304 still. Lots of head scratching. Cleared the code. Decided to replace the NEW #4 plug with one of the old 42,000 mile plugs.
Bingo. It appears the new plug itself was bad right out of the box.
2013 Weistec 540/715 tuned CLS 550, 2008 E350, and '07 Jaguar S-Type R
Wow, my hat's off to you as changing plugs on the M278 is a PITA for the average person. Incredible that a brand-new Bosche plug was defective! Glad to hear you're back in business
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