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986 Forum - The Community for Porsche Boxster & Cayman Owners (http://986forum.com/forums/)
-   Boxster General Discussions (http://986forum.com/forums/boxster-general-discussions/)
-   -   Misfires and flashing CEL (http://986forum.com/forums/boxster-general-discussions/80672-misfires-flashing-cel.html)

ecp 05-30-2021 01:35 PM
Quote:
Originally Posted by Stl-986 (Post 636460)
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.
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.

ecp 05-30-2021 03:12 PM
Quote:
Originally Posted by blue62 (Post 636462)
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.
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.

blue62 05-30-2021 03:19 PM
Quote:
Originally Posted by ecp (Post 636472)
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.

ecp 05-30-2021 03:35 PM
Quote:
Originally Posted by blue62 (Post 636475)
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?

ecp 05-30-2021 05:01 PM
Quote:
Originally Posted by Stl-986 (Post 636460)
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.
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.

blue62 05-30-2021 05:07 PM
Yes it sounds like a compression check is in order.
Let us know what you find.

ecp 05-30-2021 08:14 PM
Quote:
Originally Posted by blue62 (Post 636484)
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

ike84 05-30-2021 09:30 PM
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..

Sent from my POCOPHONE F1 using Tapatalk

ecp 05-31-2021 05:45 AM
Quote:
Originally Posted by ike84 (Post 636494)
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..

Sent from my POCOPHONE F1 using Tapatalk
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

blue62 05-31-2021 05:56 AM
Just because I am curious.
You stated that your running headers.
Do you have other modifications to the car???

ecp 05-31-2021 06:04 AM
Quote:
Originally Posted by blue62 (Post 636510)
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.

blue62 05-31-2021 06:14 AM
You could pull a fuel sample and send it out for analysis.
I don't have a clue where you would send it.

ecp 05-31-2021 07:51 AM
Quote:
Originally Posted by blue62 (Post 636514)
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

blue62 05-31-2021 08:17 AM
Quote:
Originally Posted by ecp (Post 636523)
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.

ecp 05-31-2021 08:36 AM
Quote:
Originally Posted by blue62 (Post 636525)
Keep us informed if you would.
I always like to know outcomes and causes.
Of course. praying for bad gas.

ecp 06-02-2021 07:34 AM
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.

blue62 06-02-2021 10:37 AM
Quote:
Originally Posted by ecp (Post 636653)
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.

ecp 06-03-2021 11:33 AM
Quote:
Originally Posted by blue62 (Post 636661)
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

blue62 06-03-2021 05:24 PM
Quote:
Originally Posted by ecp (Post 636740)
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:

ike84 06-03-2021 05:58 PM
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.

Sent from my POCOPHONE F1 using Tapatalk


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