Cylinder 1 / multiple cylinder misfire, any guidance?

DanSteele · 1 Aug 2019

Afternoon all.

136k '03 c4s.
I've just had flashing CEL, plugged in OB2 and got the attached pic. Stopped as soon as it happened. Misfire cylinder 1 detected (I keep ob2 in glovebox)

Drove the 4 miles home and seemed to get worse. Screenshot is when I got the car home.
Oil pressure etc ok, engine temp fine, no leaks to be seen.

The 3 variables/ potential causes...

1) I've just changed the engine mounts (yesterday) so could have disturbed something. Although was fine for the 15 mile test drive straight after
2) I had just washed the car, potential for water ingress, although didn't do anything different to usual.
3) was in a rush, I had just filled up (about a mile before it happened, deviated from the usual v power and went for Tesco momentum. Currently trying to ascertain if they have had any other issues with the fuel.

In short, filled up, made it a mile, CEL cylinder one, drove home gingerly, and screenshot of when I got home.

Thanks for you help, won't be able to get back to the car until Monday.

Dan

deMort · 1 Aug 2019

More than likely its a cracked coil which got wet and caused the misfire .. when it drys out it will probably run fine .

In short you need to have a look at all the coils to be safe as i assume the pending misfires on other cyls are old non current faults .

No.1 coil cracking is the most common due to the coolant tank overflow pipe exiting onto this coil .. if you see a rubber pipe there then push it behind the heat shielding on the body .

DanSteele · 1 Aug 2019

Many thanks deMort, I was hoping I'd get a response from the resident specialist!

Fingers crossed it's the coil pack, I'll investigate on Monday. They have been on my radar, I think they were replaced in either '15 or '13.

When I first plugged the reader in (when it first happened), I didn't screenshot, but I don't think any of the other misfires were recorded (the pending ones)
I believe they came on the limp home (didn't leave the reader connected during that drive, in hindsight I should have done)

...I could have that all wrong though , I haven't used the reader all that much yet

Dan

deMort · 1 Aug 2019

Bless you but im really nothing more than an average mechanic who tries to help out here .

For a misfire then a coil is the most obvious starting point .. at work i would tend to swop out the plug and coil at the same time and then see if it fixes the fault .. it's far quicker to do that than diagnose at that point .

After that we move on to injectors , compression etc but to be fair 9 times out of 10 its spark related and as no.1 coil is so common im pretty sure its just that .

My guess is the car has seen other misfires at some point and has flagged them as pending .. ie not a problem atm but it has been .. hence check all the coils .

To be fair if they were replaced a few years back then they should be ok .. but we start at the beginning as they say

DanSteele · 1 Aug 2019

deMort said:
For a misfire then a coil is the most obvious starting point .. at work i would tend to swop out the plug and coil at the same time and then see if it fixes the fault .. it's far quicker to do that than diagnose at that point .

Many thanks, I'll start here Monday afternoon. In the mean time I'll have a watch of a few videos / guides. On this engine, I have to admit I don't even know if the coils are accessed from above or below or what level of ancillaries need to be removed to get access.

Dan

deMort · 1 Aug 2019

It's all done from underneath ... on a ramp its ok .. jacked up and not so nice.

Nothing needs to be removed .

I lift up the rubber boot then unplug the connector .. it makes life easier when refitting ... trust me it does .

Coil bolts will often be rusty .. make sure the allen key fixing goes in far enough before undoing ... if not then i use a 90 degree pick to clean out the rust a bit .. that or knock the socket into the bolt .

A 1/4 inch ratchet with a 5 mm hex socket i think is best .. not sure if its 4 or 5 mm .. i just use what i know fits without taking notice of the size im afraid .

It's not a hard job as such .. but a bit awkward due to it being jacked up and limited room .

DanSteele · 1 Aug 2019

Top man! I'll get some glasses on this time, rust in the eye from poking at the exhaust whilst doing the engine mounts wasn't pleasant!

I'll report back with hopefully good news / I've managed to move the misfire from one cylinder to another. I'll keep the rubber boot trick in mind, I'm sure it will be one of those 'ahhh gotcha" moments once I have it in front of me (most likely about 6 inches from my face whilst underneath car)

Quick check, out of the 6, cylinder 1 is nearside rear?

Dan

deMort · 2 Aug 2019

Move the misfire ?? details please .

All Porsche,s then no.1 cyl is the left hand side of the crank pulley and closest to you .

996 and standing behind the car facing the front then no 1 is left hand side closest to you .. then 2 / 3 with right hand being 4,5 and 6 .

No.1 is also under the coolant tank

A Boxster has the engine reversed so you stand at the front of the car and do the same .

DanSteele · 2 Aug 2019

deMort said:
Move the misfire ?? details please .

Apologies, bad English, meant to say, I'll hoping to report back after managing to move misfire to a different cylinder to chase the fault. Ie swap coil pack/plug from cyl 1 to another and hope the misfire code changes.

Will order a new set of plugs and coil packs if this is the case, won't be able to get under the car until Monday afternoon to start looking at it though.

Cheers for the info on cylinder arrangement.

Dan

deMort · 2 Aug 2019

aghh okies .. i'm guessing you have email set on replies here as that was a fast response

Yup .. swapping is a good way to prove a fault .

Googles . yes a must .. it's an important lesson to learn but i still see my colleagues doing the same with no protection .. sigh .. and we do this for a living !

You would think we would know better .

DanSteele · 6 Aug 2019

Update time

Result!

Was still misfiring after being sat 4 days.
I've replaced cyl 1,2 and 3 coil packs and plugs.

Was going to swap over coil/plugs, but I had the new parts to hand and could see big cracks on 2 and 3 (incidentally, no1 didn't look bad at all)

Have to say though, what a fiddly job, who'd have thought changing engine mounts was easier than plugs. Took a bit of getting inventive with the many socket sets I have.

Will do Offside bank once exhaust has cooled. 15 miles or so driven so far without issue or faults/pending faults.

The heat shield didn't need modification to fit back on, seemed to clear them fine, date code on old coils was 2010.

Many thanks for all your help DeMort, much appreciated!!

Dan

deMort · 6 Aug 2019

I'm afraid i have the luxury of a ramp .. and it's far easier to a degree .. i still change these by touch but obviously i've done a few over the years and have the tools and the feel for it ... we get 0.8 hrs to change plugs on these .

I don't envy you guys doing it jacked up on stands .

cracked coils and yup .. they are shot .

See how you get on but it does sound like its fixed :thumb: .

DanSteele · 7 Aug 2019

Did the offside bank last night (seemed to be even less space!) coil packs were in a worse state on this side.

Went for a spirited drive after and nothing untoward to report, I'll have a 320 mile or so trip in her at the weekend, which should hopefully be more of the same

0.8 hours! That's impressive!

Looking at the state of them, and that the failure happened just shy of a few miles from the motorway, where I'd have been for 3 hours or so, I'm going to say I got lucky with the timing on this.

A ramp would have been great, on one end, I was scraping knuckles on the exhaust... whilst being bitten by ants from the driveway at the same time :x

Dan

bakerboy4s · 7 Aug 2019

My dad used to say scraped knuckles were one of the joys of motoring!!
Glad you sorted it :thumb:

deMort · 7 Aug 2019

You have my sympathies young man .. gone are the days i would jack up a car outside and try and do something like this !

Technical term for injuries like this is called "spanner rash" lol ... a common term shall we say in my trade and like all mechanics .. i have a wee bit atm

0.8 hrs is the book time for this job so all garages should charge that for a plug replacement on this model , we have a ramp though .

Most of the coils seemed to be cracked so i think you have had your money's worth out of them

Anyways .. that's a job ticked off for many years to come :thumb:

Cylinder 1 / multiple cylinder misfire, any guidance?

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