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Senior Porsche Financier
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Discussion Starter · #1 ·
... even after replacing the cyl 3 coil pack and plugs.

I'm starting to get a cylinder 3 misfire @ 1/second after getting gas, car stumbles, throws CEL but no trouble codes. The CEL persists on subsequent starts even after starting smoothly.

After a few days of restarts, the CEL is gone.

Maybe I'm due for fresh coil packs - have to see when last I addressed cyl 3.

I'm thinking fuel injector ... How difficult is it to replace injector #3 - right rear cylinder?

I am only getting this on cyl 3, ... If it were a broader warm start problem I'd guess it would hit all cylinders.

Thoughts? && Thanks!
 

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Discussion Starter · #2 ·
Update: puzzling solution

I've added about 5000 miles since I posted this. The problem was slowly getting worse.

On that 5K mile trip I'd picked up 3 coils to shotgun the right side of the engine. Lacking tools, I replaced #3 in a Walmart parking lot and called it a day. I needed more tools and access than the bare minimum of tools I bought.

And durametric still showed the only misfiring cylinder as #3, again; CEL persisted.

When I got home I replaced the other 2 packs on the right side of the engine, both were badly cracked.

In the process I worked with the battery disconnected ... So the ecu was reset.

And my misfire is generally gone. No CEL, improved gas mileage. "Generally" because I still have the occasional misfire and will replace left side coils soon. Some of them may be original to the car, @ 128K miles. Yow.

I'm still puzzled why the durametric (or the Bosch ECU) logged those misfires to cyl #3. Ducking misleading.

My mileage is indeed varying,
-PM.
 

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Re: Update: puzzling solution

I got the white (minor) PDK warning on my 987.2S several times putting it into limp mode (aka rough shift mode), two of which threw a CEL for engine misfire. Was always fine after I restarted, but when it happened twice in two consecutive days I decided to stop ignoring it. Durametric confirmed cylinder 3 was misfiring a lot, several seconds worth each day. I also put 2 & 2 together and hypothesized the drag on the driveshaft from the misfires was likely what was causing the PDK error. The coil looked good, no cracks, so I swapped coil packs between 3 & 4 to see if the misfire followed the coil pack to 4 or stayed in 3...

...and no misfires since. I drove to and from work every day for a month with my laptop connected so I could catch the error on Durametric, but nothing, no new misfires and no new PDK errors. That was 6 months ago. I can only assume the problem was a bad plug connection the whole time and swapping the coil packs fixed it. Not exactly apples:apples with your experience since we have different gen engines, but aging cracked coils misfiring (especially in wet weather) are a well known problem.
 

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Discussion Starter · #4 ·
Re: Update: puzzling solution

Yah. I don't mind replacing cracked coils, I'm just thrown by my misfires only being counted on cyl #3, as identified by the durametric, but fixed when cyl 1&2 coils were replaced. Unless that number maps to something else ... Like firing order?

Or maybe it the software isn't quite as accurate when running on a dog-slow netbook running winXP.

In any case I chased my tail for a long time.

Thanks for the thoughts!
 
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