Misfire after spark plugs - 986 Forum - The Community for Porsche Boxster & Cayman Owners

Escott1622 · 04-03-2022, 11:22 AM

I swapped my spark plugs last week 60k miles. Most likely original ones were in there. After the plugs were changed things were good for atleast 100 miles then I’d have slight hesitation when taking off from a stop in first gear but resolved itself after an hour. Then last night I was driving through a tunnel and I got on it alittle and out of no where flashing check engine light that would flash when I was heavy in the throttle. Tried restarting a few times but now the misfire stays. Codes are p0300( random misfire) p0301(cylinder 1 misfire confirmed) and p0305(cylinder 5 missfire) I ordered new spark plug tubes which I didn’t replace and will just replace those while I look around for a cause. Does anyone else have suggestions on where to look other than the classic swapping coils and plugs with other cylinders?

Escott1622 · 04-03-2022, 11:23 AM

2001 2.7l 60k miles

Stl-986 · 04-03-2022, 11:31 AM

could be a losse plug or coil or coil wire.

What plugs did you put in? Last time the coils were replaced?

Escott1622 · 04-03-2022, 11:32 AM

Quote:

Originally Posted by Stl-986

could be a losse plug or coil or coil wire.

What plugs did you put in? Last time the coils were replaced?

I forget the brand but it was decently expensive and were ones I’ve seen many use on here. And no idea on coils, If I had to guess I’d say never but when it’s back up in the air I’ll check markings

Stl-986 · 04-03-2022, 11:42 AM

Double check which plugs you used. If they weren't Bosch I would replace them with the correct ones.

Escott1622 · 04-03-2022, 11:44 AM

Quote:

Originally Posted by Stl-986

Double check which plugs you used. If they weren't Bosch I would replace them with the correct ones.

Do they really make that big of a deal? I come from bmw and Mercedes so Porsches are kinda new to me. If they are really that picky then if I got like ngk ones you suggest still putting bosch?

pilot4fn · 04-03-2022, 11:54 AM

Quote:

Originally Posted by Escott1622

Do they really make that big of a deal? I come from bmw and Mercedes so Porsches are kinda new to me. If they are really that picky then if I got like ngk ones you suggest still putting bosch?

I'd say that the Bosch plugs do not make the engine work like no other plugs. INSTEAD make sure that you have correct plugs.

I have a 2001 Boxster with 2,7 and the very best plugs I have found for the street and also several race weekends each year are there platinum tip NGK BKR6EQUP.

Previously I got info from a website to get the Bosch FGR6KQE 7413 to my Boxster, but these were not good and as I found out later these were also wrong ones.

Stl-986 · 04-03-2022, 12:03 PM

Many report good success with the NGK, but also depends on exactly which ones you got.

Honestly for the price I just go with Bosch plugs. It's simpler and it is what comes from the factory.

Since you just did plugs the issue you are having is going to be plug related....or the parts you took off/put back on as part of the process. Prefer myself to just do it once and be done with it then try to save a few dimes.

elgyqc · 04-03-2022, 12:35 PM

I would doubt that the problem is that the plugs are not Bosch. Much more likely, as suggested by STL-986, one or more coils are not properly seated on the plugs or that a coil wire is not properly inserted all the way into the connector, they can be difficult and if you don't pull the rubber boot back you can't see if it is not seated.

Benitom · 04-03-2022, 08:45 PM

Check for hairline crack in the coil - I had the same code when one of the coils was bad after spark plug change. Mine was cylinder 6 missfire.

magno_grail · 04-03-2022, 10:56 PM

Unless they changed from 1999, the coils are mounted on the plugs. There are no plug wires and you cannot pull back any rubber boot to see if they are seated.
I just worked on a Volvo Urban Assault Vehicle with a misfire on cylinder 6. Changed the plugs and swapped the coils between 5 and 6. The misfire did not move so the problem had to be the injector. Swapped injectors 5 and 6 and the misfire followed. These injectors are stupid expensive considering they are just rebranded FoMoCo parts. I used a battery to open the injector and blew it out with air from the outlet side then filled it with WD-40 and blew that through the nozzle. Misfire went away.
Any water that gets into the fuel system will cause problems as the holes in the injectors are too small to let it pass through.

Escott1622 · 04-04-2022, 05:40 AM

I ordered the new tubes like I said. I remember buying the spark plugs in store and the autozone near me Carry’s the NGK IRIDIUM ones so I think that’s what’s in it I can verify when I pull them. My starter is making a horrible screeching sound when starting so I ordered that along with rear brakes, fuel filter(probably hasn’t been changed in years), belt and filters. I also bought the tool I saw on here to remove the tubes. I was going to order all new coils but I think I’ll just replace them if I find any cracked ones. While I’m in there is it fine to keep the ngk iridium ones if that is what’s in there? I was in a rush when I did them originally that’s why I was at autozone in the first place

Stl-986 · 04-04-2022, 06:11 AM

Here is a question for you. Was it wet out, raining or drive through any puddles when you got the codes?

Believe those are the wrong NGK's. Most of the parts stores dont carry the correct ones and would need to be ordered.

Coils are not easy to detect if there are any cracks unless they are big cracks. The car should still be drivable (although badly).

Escott1622 · 04-04-2022, 06:13 AM

Quote:

Originally Posted by Stl-986

Here is a question for you. Was it wet out, raining or drive through any puddles when you got the codes?

Believe those are the wrong NGK's. Most of the parts stores dont carry the correct ones and would need to be ordered.

Coils are not easy to detect if there are any cracks unless they are big cracks. The car should still be drivable (although badly).

It was raining when the flashing check engine came on but I mentioned the hesitation that was on a nice sunny day top down. I cleared the codes that night and left it in the garage came back 24 hours later and still missfire right on startup now. Can you provide the correct spark plugs I should buy? I’ll just order them now I don’t want to mess around with the wrong ones

Stl-986 · 04-04-2022, 06:15 AM

cracked coils & rain do not mix. perfectly describes a misfire. if it were me I would just replace all 6 plugs & coils. You can get them from Pelican or fcp euro. Dealers price for the plugs isn't all that expensive either but their coil prices are.

Escott1622 · 04-04-2022, 06:19 AM

Quote:

Originally Posted by Stl-986

cracked coils & rain do not mix. perfectly describes a misfire. if it were me I would just replace all 6 plugs & coils. You can get them from Pelican or fcp euro. Dealers price for the plugs isn't all that expensive either but their coil prices are.

What exact plugs would the dealer sell? My Porsche dealer is in the city and is a pain to get to I’d prefer to order online. Is it fine to replace only one or maybe 2 coils? I know replacing all is ideal but I’d prefer to get most of the life out of the coils that remain on the engine (if they are on good working condition)

pilot4fn · 04-04-2022, 06:28 AM

Quote:

Originally Posted by Escott1622

What exact plugs would the dealer sell? My Porsche dealer is in the city and is a pain to get to I’d prefer to order online. Is it fine to replace only one or maybe 2 coils? I know replacing all is ideal but I’d prefer to get most of the life out of the coils that remain on the engine (if they are on good working condition)

platinum tip NGK BKR6EQUP.

Escott1622 · 04-04-2022, 06:30 AM

Quote:

Originally Posted by pilot4fn

platinum tip NGK BKR6EQUP.

This might be the one that’s in it. I recognize that model number either from buying or scrolling the forums here

elgyqc · 04-04-2022, 01:47 PM

Quote:

Originally Posted by magno_grail

Unless they changed from 1999, the coils are mounted on the plugs. There are no plug wires and you cannot pull back any rubber boot to see if they are seated...

I was talking about the coil wires not plug wires. There is a rubber boot over the connector that plugs into the coil and it is easy to think the connector is on all the way when it is not, hence the suggestion to pull the boot back.

magno_grail · 04-04-2022, 03:05 PM

Alright, but the connectors have a snap lock you can hear click when full seated.
Irridium plugs last longer than the cheaper ones. As long as they are the right heat range and gap the new plugs should not be causing the misfire.
Bought a new starter without finding out what the noise is from? PMGR Starter usually have a plain bush on the gearbox side and needle on the ring gear side of the output shaft. The grease in the gearbox or needle could have dried out. The armature end of the motor is commonly a bush also.
If it sounds as though the Bendix is not engaging it might need a new solenoid, about $20 from a starter supply.