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benaslan

P0300, P0303, P0305, P0306-Misfire at cold idle only

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0.018" is definitely way too small. I think it's worth changing them out with the correct spec'ed ones.

The new plugs should come pregapped but it's also good to verify before installing.

Bte, are you sure about 0.06" is proper? That's greater than 1.5mm, which sounds too much to me.

Edit: googled a bit and 0.06" indeed is the proper gap

Edited by Ahsai

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They installed different plugs than what they told you they did? Sounds like it's time to get a new mechanic who knows what they are doing.

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So, that gap is what it says in the workshop manual, but everywhere I look says half that. I just got new plugs and installed them. Need to finish putting everything together after dinner I hope. Not much left to do but that was a bit of a pain.

It was certainly clear that there was not enough room in those plugs to generate a decent spark. All the plugs were fouled, but the 3 & 6 were the worst. I labeled and kept them all.

We'll see what happens after I finish and probably take a few weeks for a misfire again to come up with new plugs! but hope it doesn't. Any recommendations from anyone for an additive to clean they crud out of my unburned cylinders?

I am torn on the mechanic. He had an injury and was out when the work was done by his new people. I'll give him a chance to respond to my email and then decide, but I'm not happy.

Edited by benaslan

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Good call replacing the plugs. How many miles on the plugs? They don't look too new judging from the rounded prongs.

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A lot of folks gap the Bosch FR6LOC plugs around ~ 0.028, but I would stick with spec in my own car. Certainly sounds like yours were too far out of spec regardless, so hopefully that's what is causing your problem (it often is the plugs and/or packs as the culprit when dealing with misfires). Hopefully you can trust that they put on new coil packs and this debacle with the plugs was just an innocent mistake.

By the way, not sure if you're running stock boost or not, but some gap tighter if running higher boost. I personally don't have any direct experience with that as I always ran stock boost and nothing but stock boost.

Edited by Silver_TT

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Those plugs were not very old. 1 year max. They didn't look old in person either (must be the pic), just very fouled (and dirty). There was almost no gap and therefore almost no spark.

I scanned the forums for plug recommendations and saw a lot of people like the NGK Iridium plugs, so I thought I'd try that since a local parts store had the one I needed-saw online inventory (BKR6EIX)- and for a good price. I gapped them at 0.032" and that should work just fine. It says the design is for improved throttle response and anti-fouling. We'll see.

Yes, the coil packs were very clearly new. I verified they are the newer version (997.602.10400/Beru 0040100036).

I took the car for a test drive and was impressed. I did get one misfire at start-up in one cylinder, but that could easily be from the gunk that's in my cylinders (it was #6).

Time will tell, but hopefully that's it for this issue. I'll try to repost again with more results. Thank you everyone for any help. Much appreciated!

***Forgot to add in here that a lot or people say the coil needs to "click" into the spark plug. There may be different coil packs, or that may be the original 996 pack, but mine sure did not. I tested with the coil out of the car and examined closely. There is a spring in the boot of the coil which looks and feels like it just presses against the plug.

Edited by benaslan

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Yes, please post updates until you are 100% sure you have solved the problem. Too often there are good threads like this that end with the original poster never following up with a conclusion.

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Just an update...

As of now, I have had no codes nor pending codes for a long time, and normally would have had a code by now. My problem is likely fixed and if it's not, I'd bet any future misfires would be due to carbon build up in my cylinders.

The following is all I have done:

1) MAF sensor. I changed this because I read that over-revs can cause it to go bad without a fault code. I got a good deal on Amazon for the exact Bosch part.

2) Fuel Cap. It was clearly old and the o-ring was extremely cracked and dried out.

3) New (and correct) plugs that were gapped at a more appropriate range. The plugs that were in there were Beru 5's and I replaced them with the 6 range in the plugs mentioned above.

I've done my best to open up the throttle to clean out the crap, but I have only had one longer drive, so not a whole lot of opportunity to do so other than a few midday ownership of the fwy...

I'll post again if there is any future change.

Thanks for all the input!

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Just an update...

As of now, I have had no codes nor pending codes for a long time, and normally would have had a code by now. My problem is likely fixed and if it's not, I'd bet any future misfires would be due to carbon build up in my cylinders.

The following is all I have done:

1) MAF sensor. I changed this because I read that over-revs can cause it to go bad without a fault code. I got a good deal on Amazon for the exact Bosch part.

2) Fuel Cap. It was clearly old and the o-ring was extremely cracked and dried out.

3) New (and correct) plugs that were gapped at a more appropriate range. The plugs that were in there were Beru 5's and I replaced them with the 6 range in the plugs mentioned above.

I've done my best to open up the throttle to clean out the crap, but I have only had one longer drive, so not a whole lot of opportunity to do so other than a few midday ownership of the fwy...

I'll post again if there is any future change.

Thanks for all the input!

Replaced the Coils and Sparkplugs also resolved my misfires during a cold start-up. Thanks to this thread it helped resolve my problem.

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And another update to this thread...

So, after bit, my misfires came back. If I drove a lot in a day, or went on a long drive, no CEL for a few days. Something was still up though. I ran Techron through a few tanks worth and no change.... Was driving me crazy to still see the light. I am sure the other fixes helped, but there was something still going on. I had a enough and took it into another shop I had used before.

It want cheap, but he was confident he could figure it out and it seems like he did. He did a smoke test on the intake and found several small leaks and fixed them (loose hose clamps and such). I bet Carlsen Porsche didn't tighten everything properly when they had my engine out for some trans work some years back. The problem started intermittently after their work, but it was not immediately after so I was never sure.

Car sounds night and day different at startup now... Hopefully no future updates to this thread.

Edited by benaslan

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