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So yesterday as I was nearing home, the car stumbled pulling away from a stoplight and the check engine light flashed and then stayed lit. Two minutes later I pulled into the garage and the idle was rough, with a sort of pulsing/missing exhaust note. The Durametric reads two fault codes:
- P0300 / 507 - Misfire detection
- P0304 / 511 - Misfire cylinder 4

That seems pretty clear. Likely bad plug or coil on cylinder 4, right? Did my very short drive to work & back today, and it stumbles noticeably from every stop. My inclination is to just replace all the plugs myself ASAP, since it has been a while. It sounds easy except for awkwardness of accessing the two forward plugs. If this sounds reasonable, my questions would be:
- Full replacement could be 6x of plug, coil (or just plug connector), and spark plug tube -- is all that overkill?
(Or does it make sense to just get 1 $40 coil in case #4 coil is cause?)
- Is cylinder 4 the front driver side cylinder? (#4 will deserve the most scrutiny.)
- Go with the standard Beru plugs or is there a perfectly good locally available alternative?

Thanks for advice,
Trygve

Quote
Trygve (Alameda, CA)
So yesterday as I was nearing home, the car stumbled pulling away from a stoplight and the check engine light flashed and then stayed lit. Two minutes later I pulled into the garage and the idle was rough, with a sort of pulsing/missing exhaust note. The Durametric reads two fault codes:
- P0300 / 507 - Misfire detection
- P0304 / 511 - Misfire cylinder 4

That seems pretty clear. Likely bad plug or coil on cylinder 4, right? Did my very short drive to work & back today, and it stumbles noticeably from every stop. My inclination is to just replace all the plugs myself ASAP, since it has been a while. It sounds easy except for awkwardness of accessing the two forward plugs. If this sounds reasonable, my questions would be:
- Full replacement could be 6x of plug, coil (or just plug connector), and spark plug tube -- is all that overkill?
(Or does it make sense to just get 1 $40 coil in case #4 coil is cause?)
- Is cylinder 4 the front driver side cylinder? (#4 will deserve the most scrutiny.)
- Go with the standard Beru plugs or is there a perfectly good locally available alternative?

Thanks for advice,
Trygve

Trygve:

Cylinder 4 is the first cylinder at the front of the engine on the driver's side (left side).

Before you go any further, I would swap the ignition coils between cylinders 4 and 5 and see if the fault code follows the problem to cylinder # 5 (middle cylinder on left (driver's) side).

If nothing changes, I would then try swapping spark plugs between #4 and 5.

That should help you pinpoint it.

As far as replacing all the coils, plugs, tubes and seals, how much mileage and age on all of those?

If you can pinpoint the problem, whether it's the plug or coil, you can replace that one first and then you'll have time to decide whether you want to change all the other parts.

Regards, Maurice.

Thanks, Maurice, that makes perfect sense. I'll try swapping #4 and #5 coils, and if there's no change, then those two spark plugs.

I need to dig into my maintenance records -- honestly I cannot say when the plugs where last changed. My guess would be at 120K, which is 15K ago, but I need to look it up. The other parts, I don't know unless they are routinely change with the plugs by the dealer (doubt it). Probably muuuuchhh older. I do recall having a leaky spark plug o-ring replacement eons ago. (On a 13-yo car, such repairs become forgotten historical lore!)

Marc, it looks like a coil is $40, so it's worth avoiding needless replacement of good ones for sure. But I like Bob's idea that if it's the plug, maybe replacing all the plugs is sensible. Esp. considering that I have had an AOS-like tailpipe smoking problem (new AOS did not fix it) and maybe something(s) got fouled.

or a metal finish/treatment that is intended to prevent the spark plug from sticking in the threads in the head.

When the plug is removed this coating is disturbed and if the plug is reinstalled either in the same hole or a different one the thread protection may be reduced. In fact I just examined an old plug and the plug. The old plugs thread flanks very clearly show abrasion and corrosion in spots. The new plug's thread flanks of course show a nice nearly shiny surface finish.

Plugs to me are: remove 'em, throw 'em away, install new ones.

You can swap coils around but some claim this handling can compromise an older coil. IOWs, well if these experts are right even if the coil was ok to begin with the handling may compromise the coil and then you may be misled into believing something else is at the source of the symptom you are seeking to identify.

One thing you can do is fill a spray bottle with distilled water and use this to spritz down the cold coils. Then start the engine. If any coils are bad, bad enough to be affected by the water, you'll know it.

Anyhow, I believe that as with plugs the same is with coils. If you have reason to suspect one or more coils the suspected coils are removed and replaced.

And if one is not sure if a coil or plug is bad to the point either one needs to be removed to me that is sufficient grounds to simpy replace the suspected plug or coil.

If you go with a new set of coils and plugs you have eliminated two possible sources of engine troubles. Plus when you remove the plugs you note each plug's condition. This can help you identify cylinders that may have combustion (or other) issues.

If engine troubles remain, persist, then the problem lies elsewhere. (Ignoring the real but very low risk one of the new replacement coils or plugs is defective.)

Sincerely,

MarcW.

The thread coating is just a bit of anti-sieze. No big deal, nothing mysterious or exotic and nothing to worry about. You can always put a little on the threads of the plug after removing it for inspection. Likewise, no need to toss a plug simply because you took it out to look at it. Unless you spot a problem, there's no reason it can't be reinstalled. By the same token, if you find a bad coil, no need to replace all the others.

have examined. The plug threads are plated, or have some surface treatment, that protects the threads of the head and the plug (dissimular metals) from the electrolysis and plain old corrosion that can occur over time and yet not interfere with the considerable heat transfer that takes place as the plug sheds its heat load through its thread contact with the threads in the head, which of course is water cooled.

There is no real need to remove plugs to look at them. They need to be changed on some schedule but I seriously doubt anyone can tell much from looking at just one plug. If so I would expect the CEL to be on and at least one misfire code logged for the cylinder with the bad plug.

Besides it only makes sense to look at all 6 plugs. Looking at all 6 gives one some sense of what is normal and what is not normal, the idea being there's one plug that is questionable.

Then too really, how often does one plug fail?

As for coils, if one is bad -- unless it went bad early in its life -- the odds are great if one is bad the others can't be far behind. Everyone is different but I'm not that fond of getting into the engine compartment to replace one coil then having to do this again, and perhaps again, and again, when the other coils follow suite. May not be a hardship for some but for others (like me) I am very busy and do not have the time to be under the in my spare time. Also, since I'm out and about in my cars sometimes great distances from my home, I do not want to have to deal with perhaps replacing a plug in a motel parking lot some dark and wet night. I bought the car to sit in the driver's seat and enjoy the vehicle, not to spend time under the car wenching on it.

Then too as with other things that are replicated through the engine (plugs, O2 sensors, even converters), an argument can be made that replacing one bad and probably very old and high miles coil with a new one while leaving all the rest in service, which while they are not acting up are very old themselves and have the same high miles on them, results in an imbalance between the cylinders that will have the engine performing below its potential.

Since the engine controller only has the ability to monitor the performance of the cylinder banks if one plug is now new and the others old, the engine controller will tailor the fueling of the 3 cylinders of that bank to accomodate the worse performing cylinders. Chances are these will be the 2 with the old plugs. So one goes to the trouble and expense of replacing the old and bad plug with a new one yet the full benefit of this change is not realized because the engine controller is fighting to fuel the other two cylinders in a manner that the entire bank delivers acceptable exhaust gases as reported by the O2 sensors of that bank. If the plugs are not firing hot enough the exhaust gas will contain too much unburned fuel, too little oxygen. So the controller will lean out all cylinders on that bank. Now the 2 cylinders with the old plugs are running a bit lean along with the cylinder with the new plug. Only it is running leaner and probably hotter cause its plug is new and the combustion in that cylinder is more complete.

Replacing just one plug or one coil may be ok for a utility vehicle like an ancient Ford F150 pickup but for a modern high performance sports car like the Boxster it makes no real sense and is probably a false economy.

Sincerely,

MarcW.

it is much more fun jumping to erroneous conclusions.....

recent. (The Boxster generated its first misfire error codes the other day. And wonder of wonders, so did the Turbo. Must be something in the air.)

In the case of your car, that the engine continues to run rough suggests the misfires are not transistory but due to a coil (or plug) breakdown. My money is on a coil, though.

Thus if I were you I would simply replace the offending coil.

If the plugs are close to being due to be changed I'd replace all of them. While you are there examine every coil using the #4 coil as a benchmark and replace any that have a similar look to them.

Or jsut replace all 6. However, the cost though is something to consider. I don't recall how much I was quoted for coils but I do remember deciding to clear the error codes and see if they come back. ('course, the coils in my 02 Boxster have been in there since day one and the car is coming up on 240K miles.) So far they have not and the engine continues to run just fine. (Did the same to the Turbo and it has remained misfire free too.)

Check with your local Porsche dealer parts manager. I believe the part # for the Boxster coils has changed and the new one starts with a '997'.

As for plugs the car has had several sets of plugs now (the car almost has 240K miles on it) and all have been whatever the dealer's parts counter supplies. I happen to have an old set on my desk and they are Beru ultra,R6 336. Since the plugs have never given me any problems and last the 60K miles or whatever the replacement schedule calls for I see no reason to experiement with something else.

But it is up to you what plugs you want to use. In fact, I think I have a set of brand new (though I bought them several years ago) Bosch Super R5 685 plugs that if you are interested in I'll make a good deal on. I'm not going to use them.

Sincerely,

MarcW.

Edited 1 time(s). Last edit at 02/26/2011 12:22PM by Laz. (view changes)

Furthermore, my info is that few if any stations carry real 'E10', that is E10 with an ethanol content of 10%.

When E10 was mandated gasoline refiners were reluctant to just spring E10 on the public and have so far limited the ethanol content (max.) to under 10%, with around 7% to 8% being the highest percentage of ethanol in E10 gasoline. (Even now there is some pushback to avoid having to offer E15 or anything close to it.)

The Boxster misfired after I treated it to a couple of short trips, the last one just a few hundred feet as I moved it from its uncovered parking space to a covered one just before I left town in the other car. Upon my return to town a few days later when I went to move the Boxster almost immediately after startup the misfires happened with the engine very obviously misfiring, well, running uncharacteristically rough. But thankfully the engine's behavior improved quite quickly and the engine's behavior has been just fine since then.

The Turbo sat outside in a heavy rain all night in a Santa Clara motel parking lot and when I got in the car early the next morning -- with the rain still coming down -- immediately upon engine start the serpentine belt squealed (it does this after I wash the car too) and the check engine light came on. I do not recall the engine exhibiting any obvious misfiring behavior certainly no behavior as as severe as those by the Boxster engine.

Since the Turbo is under warranty I checked with my dealer's service department and was advised to just clear the error codes (I wrote them down before I cleared them) and see if they come back. The car is covered by its CPO warranty until June of this year, so I have some time. So far the error codes no error codes have appeared. The Turbo got new plugs not too long ago (well, now that I think about it about 20K miles ago) while the coils are original. I have been advised by some Turbo owners/experts the coils should be replaced everytime the plugs are changed but I talked this over with my Porsche tech contacts and they tell me they seldom encounter bad Turbo coils and advised me to continue to run the orignals. When the plugs were changed the tech examined the coils and reported he could find no reason to advise me to replace them, either at my expense or under warranty.

As for the Boxster, since a project I'm working on involves communicating with vehicles that have the CEL on and one or more DTCs (the more the merrier!) and freeze frame data I left the Boxster check engine light on and the 5 error codes (one P0430 and 4 misfire related codes) unerased.

As a side task, I'm seeing if the check engine light or any of the misfire codes will self-clear.

Sincerely,

MarcW.

I had the same problem with cyl 6 and replaced the coil, a few weeks later I had the same code on another cylinder. At that point I decided to replace all of them and be done with it.

or early failure, I agree.

I do not like moving/switching plugs around and the less the coils are handled the better too.

If I remove a plug I want to replace it.

If I suspect one (or more coils are bad) and as I mentioned above the one bad coil is not a fluke I'd just replace all 6 and be done with it.

Sincerely,

MarcW.

I recently had my '01 F-150 start running rough. No CEL, but cutting out around 2500 RPM. A day later, the CEL came on and it also had a cylinder misfire code. I talked to my mechanic as some of these coils are a pain to access due to the injector rails. He mentioned that Ford recommended replacing all 8 if 4 or more had failed. I scratched my head and wondered how you could run with 4 failed coils and he laughed. I replaced the single bad coil and she purrs like a kitten again.

warms up and the symptoms of a bad coil may not appear for a while.

Also, remember the predicament Ford (any automaker) is in. The labor to replace one coil (or plug) is about the same to replace all coils (or plugs) in at least that same bank.

But to replace just one coil say then have the customer come back with another bad coil on that same bank... well, you just know there's going to be some suspicion on the part of the customer that the other coils were just fine before the one coil was replaced, that the tech in replacing one bad coil disturbed the other coils and that's the reason one or more is now acting up.

Now if one is doing the work himself, he can play around with doing one at a time. But even though who wants to be at the engine off and on doing one coil at a time?

Sincerely,

MarcW.

These cars are not so esoteric that one can not do normal troubleshooting.

Swap coils or buy one new one and swap it in.

If your plugs are old, certainly consider replacing all six (after you determine you have a plug problem).

One bad coil does not mean the other five are ready to go. the coils receive a small voltage signal and fire accordingly, Not a big deal.

BTW, None of the coils or plug on the Boxster are that difficult to get to. Yes, relatively speaking, the forward plugs are more difficult to get to than some of the others but none are show stoppers.

Good luck.

dghii
2000 Boxster S 6speed 112k miles

Swapped the #4 and #5 coils. Both looked clean and dry, as did the tubes. (Along the way, I discovered a broken rear sway bar! 2nd time for that, previous time was at a track event.)

Anyway. Started the car. Could hear the same "beating air" sound in the exhaust. Let it run for a few minutes, occasionally applying a little throttle. Didn't sound right. But no CEL yet. Here's where it gets funny. I started to put the wheel back on and noticed that I had forgotten to plug the #4 coil wire back in!

Reconnected #4, no difference! Replaced wheel, went for test drive. Still runs bad as before, poor idle, hesitating stumbling acceleration. Finally, upon accelerating hard from a stop, it really stumbled and threw the CEL. This time it's for #5! So the coil is the likely culprit and I now know how to replace it pretty easily.

A small detail. The original CEL readout was:
P0300 / 507 misfire detection
P0304 / 511 misfire on #4
Later the following were also added to the Durametric readout, which I had to look up on the web because the Durametric did not know their meanings:
P1319 misfire emission relevant
P1316 misfire #4 emission relevant
After clearing those and doing the test drive, the new CEL codes were only:
P1319 misfire emission relevant
P1317 misfire #5 emission relevant

Sounds like you may have found the problem... Keep us posted!

Regards, Maurice.

Well, I got called away for work to Sydney, Australia, the day of my coil swapping tests. Replacement coil will be waiting for me when I arrive home. (Also ordering a spare coil, and 7 plugs so I can do the plugs myself next time and have a spare on hand.) Then all I have to do before racing season is fix my suspension rattles and newly discovered broken sway bar, etc.!