sdwtchlvr

Just ran a quick errand to the bank and when I got back into the car and started it, the idle was quite rough with shaking. The check engine light came on right after. RPMs at idle are about 650. It seems to drive fine but the exhaust sounds like a low sounding chopper blade...definitely louder than normal. The check engine light started to flash after driving but then stayed solid.

Taking it in on Monday but thought I'd pick your brains here while I wait. Any ideas?

Racin_fool

with the check engine light flashing, it is probably misfiring. Its meant to catch your attention and let you know something bad is happening. Did you recently top up with fuel somewhere? Has it been parked for a while or is it a daily driver?

sdwtchlvr

Actually, there is a service station near my house that was recently converted from a USA gas station to a Shell station, they just re-opened a week ago or so. I filled up the tank there on Wednesday, Shell V-Power premium. I typically use Chevron premium. It's not a daily driver but doesn't sit either. Drive probably 150 miles/week.

sdwtchlvr

I texted my mechanic and he mentioned maybe just a bad coil. He's closed till Monday. When I got to work yesterday I noticed it idling rough and shaking when I pulled in. I turned it off, then on again and I swore the check engine light flashed on but then went off and it was idling ok. When I left work last night it was fine. Drove to work this morning and it was fine. I work about 15 miles from home.

Aussiesuede

For some peace of mind, stop by your local chain auto parts store and ask to use their code reader. It's free. You'll plug it into your OBDII port which is located to the left of the steering wheel, beneath the dash, just forward of the Parking Brake Release lever. If they aren't too busy, a clerk will usually plug it in and read the codes for you. Anytime a Check Engine light comes on, a stored code is produced, even if the Check Engine light subsequently disappears. The codes will tell you exactly what's misbehaving.

sdwtchlvr

I've got a Carista module and I believe I can get basic OBD2 diagnostics. I'll check it out when I get home.

sdwtchlvr

Pulled these codes just now...

P0358: Ignition Coil "H" Primary/Second Circuit
P0308: Cylinder 8 Misfire Detected

Bad ignition coil on cylinder 8?

kbob999

Almost certain a bad coil. You can pick them up used on eBay for less than $20. I keep a spare on my shelf.
Try swapping coil #8 with #6 and see if the problem moves with it.
I would not drive it much with the bad coil...could wash the cylinder with fuel and lose lubrication.

https://rover.ebay.com/rover/0/0/0?m...2F130490534441

sdwtchlvr

Ok, thank you! I'm swamped with work for the next week so my DIY time is limited. But I also don't want to hand over $300+ to a mechanic for a job I can do in 30 minutes. I'll see about sourcing an acceptable part locally and getting to it when I can.

sdwtchlvr

Actually, I just popped the ignition coil off in about 10 minutes...surprisingly basic. Cylinder 8 is the back (closest to windshield) on driver side, is that correct? A local parts store has a delphi replacement for $65. Will be stopping by there shortly.

Aussiesuede

Yep. That's cylinder #8. And here is a pic of the cylinder & firing order for future reference:

aeb28

I had a similar problem a couple years back, misfire codes an all. It ended up being a sensor in the fuel system. I ended up having to take it in to the dealership to have it worked on, so unfortunately I do not recall exactly what it was. Replacing that sensor did solve the problem and at a small fraction of the cost had it been coil packs.

Edit: I do remember the dealership having a hard time finding the problem, the mechanic told me there was no code being thrown to indicate the problem sensor.

sdwtchlvr

Appreciate the help guys. I have the new coil with me so I'll pop that on when I get home this evening and see if that does the trick. If not, I will take it in to my guy on Monday morning. Figure if it's not the coil, I can install the old one and hold onto the new one for future use.

I'm sure this is a stupid question, but when I went to remove the old coil the rubber sleeve on the bottom of the coil that goes down to the spark plug (I presume) was in the shaft quite snugly and I wasn't totally confident in what I was doing so I just left the rubber sleeve and pulled off the coil. I didn't want to tear anything. The new coil I bought has a rubber sleeve. I should just yank on the old one to remove and install the new coil/rubber sleeve complete, right? Anything I should be mindful of? Edit: Just watched a youtube...I'm good. lol

sdwtchlvr

Popped the new coil in there and cleared the code. So far so good. Will report back if anything changes.

UPDATE: After a couple days of driving, it's been solid. Actually, it's been running better than ever. Could it have been that the coil on cylinder 8 was going out for a while? What are the typical symptoms, if any, of a bad coil starting to go before it fails completely?

Looser

2014 W212, Same Problem as all have mentioned, the car starts to shake and check engine light comes on. turn car off problem goes away.
after much research "forum Surfing" decided to replace the Coils and Plugs, apparently the plugs are only good to 60K. our car has 45K on it as of now 05-05-2022
Let me tell you removing the Manifold Intake / plenum to do the plugs was a M.F. and yes it's possible to do it without doing the intake but we replaced gaskets and solved oil leaks at the front of the block at the same time.
O.K. all that said, today the wife calls, same problem again. Car shaking, obviously a misfire condition right. Zero Codes, tried starting the car to replicate the problem. nothing.
What else can be the issue ?