Misfires and flashing CEL
 

Hello,
this is my first time posting on the forum. i’ve had my boxster (03 S) for about 10 months and i’ve done a lot of maintenance and work on it. it’s been driving really well and hasn’t given me any major issues until today. My tank was just about empty with the fuel light on, so i stopped and filled my tank. i only ever use 93. i pulled out of the gas station and got it up to about 6k until it lost power and had a big backfire out of the exhaust. the car had been up to operating temperature for a good 30 minutes, and i had only stopped for maybe 5 minutes to refuel. i had to have the car towed and it runs awfully. I had 3 codes show, random misfire, misfire on cylinder 2 and misfire on cylinder 1. i disconnected the coil packs on cylinders one, and then two. each time i fired the car up it sounded the same. i replaced the plugs and no change. coil packs were replaced in august, they’re still in excellent condition.

since i’ve owned the car i have done the IMS and chain tensioners so i don’t see how that could be an issue. But then again the sound reminds me of when a spark plug popped out of the head on my old vw bug.

I’m usually good at diagnosing issues on this car but this time i’m truly stumped and i’d greatly appreciate any feedback or input.

Try clearing the codes and seeing if they come back.

Is the place you got gas from a usual location/brand you usually get it from?

just to be sure it's good to post the actual codes set and any pending codes. It sounds like you were getting p0300, p0301 & p0302 but the actual codes help verify it isn't anything else.

Usual place yes. Cleared them and reset the ecu, came back instantly. It stopped flashing though. codes are p0300, p0301, p0302, p0303. seems like the issue is isolated to bank one.

really hoping it’s not something major. i might try swapping the bank one and two coil packs and seeing what happens.

as the motor cooled down it got more and more difficult to start. i’d have to crank it a bit and it would sort of chug. lots of vibrations.

when mine did that I had a chewed fuel injector wire,..Frank

easy thing would be to swap coil from cylinder 1 to anything on bank 2. clear the codes and see if it follows. If not then you know plugs & coils are good.

Next would be wiring.

Do you have a durametric? You could watch the number of misfires on each cylinder.

I would let it cool down overnight and then in the morning clear the codes, then start the engine. Does it run bad for the first 2-3 minutes or does it run good and then after 2-3 minutes run bad?

http://986forum.com/forums/boxster-general-discussions/28644-1998-boxster-p0301-p0303-odb-2-reading.html

I hope you are not having the same problem described in this post.

i suppose fortunately that doesn’t describe exactly what’s going on. the car cooled down all the way to where the SAI pump kicked on like it does on a cold start and it ran equally like garbage. going to swap coil packs, check vacuum leaks and then move onto wiring. seems like a fun weekend ahead!

I would say you're either getting to much air or too little fuel to bank 1. Check vacuum leaks. If not that, then it's likely a fueling issue. Gas.near.me has been particularly ****************ty since the shortage, even 93 octane. Try running a bottle of techron or seafoam. If that doesn't fix it, I would consider replacing the fuel filter and then the injectors.

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I’m around atlanta so we got hit with a shortage too. Checked for vacuum leaks, didn’t find any. ran the engine while spraying starter fluid inside the hole for the valve on the intake boot and the rpms increased but it didn’t smooth out at all. i’m wondering if the noise it makes is a dead injector? at idle it’s quiet, but when you open the throttle at all it’s a bad clunk clunk. I can attach a video if it would be more helpful

The occurrence of a backfire after filling with gas points to an open purge solenoid that allowed gas to enter your intake. The backfire could have damaged your intake or its gaskets, leading to vacuum leaks. Sorry, I am not familiar with the evap systems in Boxsters, this is just general automotive advice. I would smoke test the intake.

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I do have an occasional howling by the fuel tank, which to my understanding is where that solenoid would be located. i’ll see if i can get my hands on a smoker for the intake. maybe it failed all together and there’s some kind of vapor lock?
i know this is a completely different animal but i’ve had it happen on my old vws

my bank two primary o2 only reads about .04 volts and doesn’t change. the bank one sensor works properly with fluctuating values. I don’t know if this has anything to do with it. I replaced all o2s in december.

I wish i had a durametric. It’s been on my shopping list for a while, but i was about to do a full suspension refresh. I might have found something as my bank two o2 sensor is reading nothing, but confirmed it was working by swapping it with bank one. seems like that might be the dead cylinder, but the why is now the big scary question. bank one gets a normal o2 reading, but yet that’s the side i’m getting misfire codes for. I’m still stumped. Pulled all the injectors and verified they’re all working and resistance tested them, they all seemed okay, except cylinder one injector smelled like burnt electronics.... and had the most visible deposits on it. i’ve already ordered a new set.

Video of engine sound
 

Here is the link to the video of my engine. any thoughts would be greatly appreciated
https://youtube.com/shorts/TdszKNnrBtM?feature=share

If bank 2 O2 Sensor gave no signal in bank 2 but it did when you switched it to bank 1 then the sensor works.
So you have a wiring problem on bank 2 O2 sensor wiring.

Sounds like you have multiple issues.

What cylinder are you saying is dead.??? And why do you think it is dead????

Did you get a code for the bank 2 O2 sensor not working???

I have aftermarket headers, and the o2 attaches onto the pipe coming off cylinder 6. i have no o2 codes. I think the cylinder is dead because there is no signal coming off that sensor even after i’ve verified it works. so if there is no combustion happening it would read close to .0v like it is? I pulled cam plugs and verified that the can timing isn’t out since everything lined up with my locking tools from the ims kit.

I’m going to try and see if it is a wiring issue with the o2 circuit, but i dont see how it would just fail out of the blue, but anything is possible i guess. I tried attaching a link to a video i posted on youtube showing how the car sounds and runs but i don’t think it let me post it

Get an eye dropper full of water and drip a couple of drops on the header tube for the cylinder you think is dead while the engine is warm and running; if the cylinder is dead, the water will just sit there, if it is working, it will flash off as steam.

I’ll give it a shot when i get the injectors back in and fire it up again.

any tips on double checking the wiring? I did continuity test on all injector plugs to rule out a short, resistance tested coils and they were all .9ohm. they’re recently new beru packs.

Curious why you think it's the injectors. From reading it looks like you have at least a wiring issue with the o2 sensor.

What sensor on the cylinder are you referring to?

do what JFP suggests. Very much doubt you have a bad cylinder as you would have more problems and noises if so.

To test the injectors the best thing to use is a NOID. It will tell you if an injector is getting power. You can also bench test each injector to see if they at least work, which I bet they all do.

Those O2 sensors should be 4 wire sensors.
On a 4 wire look for two wires of the same color they are the heater circuit.
They should show 12v with key on.
Of the other two one is ground.
The other one is the signal wire back to the DME/ECU
Hope that helps.

I have gone back and re- read your posts in this thread.
In post #12 you stated that the O2 sensor voltage was .04
In post #13 you state it is reading nothing.
In post # 15 you state there is no signal but the voltage is close to .0v
Seems that the bank 2 sensor is working.

These O2 sensors work in a very very narrow range.
You stated you have not gotten any O2 sensor codes so my guess (after re reading your posts) is that the wiring is fine.
You could back prob the harness to sensor connection from the sensor side of the connection and check the two wires that are the same color. you should get 12v or near battery voltage with key on.
If that circuit (heater circuit) is good I would bet that the wiring is good. But that Cyl. may be dead as you stated.

If you think you have a dead Cyl. you can check it with a compression gauge.
Or use a vacuum gauge hooked up to the intake.
The needle will tick every time the dead cyl. comes up on the compression stroke.
Compression gauge will be easier if your not familiar with reading vacuum gauge needle action.

Or as JFP stated water on the exhaust for that cyl.

i figured if it’s not spark, it’s probably fuel. this car is my baby and my daily so i am just distraught and frustrated. there is an ugly noise, if i could figure out how to share the youtube link. i bench tested and cleaned all injectors. they all work and all have a good spray. there was a good amount of junk that came out of them though. dark fluid. one of them smelled funky and had more deposits than the other, but still worked when i had it hooked up.

my aftermarket exhaust has the primary o2 sensor running off the cyl. 6 pipe before it merges. might be time to extend the wires and attach to the port after the merge for more accurate a/f instead of one cylinder.

Got it running. it’s cylinders one and two that are dead. confirmed with water trick. o2 sensors reading normal. p0303 gone. all i’m left with is p0300, p0301, p0302.

could it possibly be spark or injector wiring? i don’t know how two cylinders would die at the same time.

you could use a Digital volt meter at the injector to see if you getting voltage with engine running. Or do the same at the coils.
Once you know which is the issue you can start to trouble shoot the wiring.
You could pull the fuel pump relay and just crank the motor.
BUT you want to make sure that relay does not also supply injector voltage.

Or do a simple compression test at those two cyl. just to make sure the direction to go.

Mice love to chew wires for some reason could be vermon chewed the wiring.

I’ll run a compression test tomorrow if poking around with the wiring doesn’t fan out. which terminals should i be testing on the coil for voltage. and i’m assuming i should be getting 12v on the coil and somewhere around 5v for injectors?

coils and injectors are both getting power. i don’t know how two cylinders would both lose compression at the same time if that’s the case. and unfortunately it seems that way until i do a compression test.

Yes it sounds like a compression check is in order.
Let us know what you find.

zero compression on cylinders one and two, 150 on three. didn’t bother with the rest.

i still can’t understand how they’d just blow at the same time like that. this is a 3 chain motor so i don’t know if that would make a difference or not

Loss of compression in two adjoining cylinders often points to a communication between the two, such as a cracked head, cracked cylinder, etc. I suppose it's possible that ****************ty fuel caused donation and wrecked something..

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I think I’m going to have to send it to porsche. if it does turn out to be fuel i’ll want to go the dealership route. it’s a real bummer, i was planning a road trip june 18th and was completely redoing the suspension before hand. Fingers crossed there is bad gas.... i can’t afford anything else

Just because I am curious.
You stated that your running headers.
Do you have other modifications to the car???

just a 74mm TB and plenum, everything else is stock.

You could pull a fuel sample and send it out for analysis.
I don't have a clue where you would send it.

I’m having the car towed to the dealer. the service guy said having two cylinders go out like that is strange, but of course they want to get paid also. fingers crossed for bad gas at this point

Keep us informed if you would.
I always like to know outcomes and causes.

Of course. praying for bad gas.

Still waiting to hear back from the dealership. I have a claim open with racetrac, so everything is set if they determine gas caused the damage to the engine.

I’m not going to lie i’m very nervous, but while i wait to hear back from them i was wondering if you guys had any thoughts on what the cause could be.

Basically, what do you think could have caused two cylinders (one and two) to die instantly and have zero compression?

My theory is, maybe low grade fuel or water caused a rapid change in the engine timing, detonation, possibly a cracked head or chipped or bent valve, or water spraying onto the hot valves causing a a valve to chip or warp.
I keep leaning towards bad gas simply because my tank was empty (gas light on) and it broke while leaving the station.
whatever the cause i know it was catastrophic, and there was no indication at all of issues prior to filling my tank.

Pretty tough to say without a visual inspection of the internals.
Water could do it. It (steam) can cause some very high pressures.
Broken Cam. Could do it.
Something that would kill those two Cylinders yet allow the engine to turn over and still run.
One can only guess at this point.

It's interesting and I am also curious as to what happened.

They said they took a fuel sample and it looked okay. They wanted to drain the fuel tank and replace the plugs (for $822, which is almost my whole paycheck) and since i’d already changed them i asked to just drain the tank instead. hopefully they’ll find something in there.

I’ll post an update whenever i know something new

So if you have 2 cylinders with O compression why are they wanting to replace plugs:confused::confused::confused:

I agree with blues last post, that's really really dumb (and a rip off!) For Fuchs sake, that's $60 worth of parts. They're a pain to get at but drop the headers and you'll be done with both sides in under 2 hours.

I once worked on a truck that we couldn't quite figure out why it kept misfiring - replaced the plugs, cleaned the injectors, timed the distributor, still misfiring.

On a whim I suggested we drop the fuel tank - it was a total nightmare. Rust, mud, a rag (?!?)... Put a new tank in, truck ran perfect.

Anyway, bad gas (or not enough gas) causes problems. Lots of possibilities (I truly hope you haven't cracked your head or a cylinder wall) but I don't think that spark plugs are where to start. And ignoring a total loss of compression in adjacent cylinders is just dumb.

FWIW, I recently convinced myself I cracked the head and tried finding every article on the subject pertaining to these cars. It's virtually unheard of, even by the guys who rebuild these engines for a living. Cylinder scoring, yes. Trashed valves, yes But not head damage or blown gadgets.

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