Rennteam 2.0 - EN - Forum - Boxster Misfire - Page1

Oct 7, 2005 7:51:43 AM

RascalRuss: Newbie; Loc: UK; Posts: 8, Gallery; Registered on: Oct 6, 2005

Boxster Misfire

Hi All,

Wonder if some of you might be able to give me some help.

I have a Boxster 1998 2.5l, and the last couple of weeks its been drinking the fuel heavily, gaining alot of soot in the exhaust, and smelling of very high emissions.

I took it for a diagnostics check at the local garage (Porsche) and the error messages that were coming up are, 1, O2 Sensor ouot of range, 2, Cyl 1 misfire, 3, Cyl 2 misfire, 4, Cyl 3 misfire.

The bloke at the garage send that it is not the o2 sensor that has broke, and it will only be one of the cylinder that is misfiring, but the computer registers the full bank as misfiring.

He said it could be something as simple as the spark plug, or it could be as major as weak compression.

It is due to go in Monday to try and find out the cause and which cylinder, however in the mean time over the weekend, if there any thing I can check for that might be causing the problem.

I would be grateful of any help

Many Thanks

Russ

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Oct 7, 2005 12:48:55 PM

RascalRuss: Newbie; Loc: UK; Posts: 8, Gallery; Registered on: Oct 6, 2005; Reply to: RascalRuss

Re: Boxster Misfire

Any help at all on this guys??

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Oct 7, 2005 2:08:56 PM

wtsnet: Rennteam Pro; Loc: Bath, UK; Posts: 2430, Gallery; Registered on: Nov 19, 2004; Reply to: RascalRuss

Re: Boxster Misfire

Sorry, no! But let us know how you get on.

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Oct 7, 2005 2:30:55 PM

964C2: Expert; Loc: Dallas, TX , United States; Posts: 1825, Gallery; Registered on: May 11, 2004; Reply to: RascalRuss

Re: Boxster Misfire

Quote:
RascalRuss said:
Hi All,

Wonder if some of you might be able to give me some help.

I have a Boxster 1998 2.5l, and the last couple of weeks its been drinking the fuel heavily, gaining alot of soot in the exhaust, and smelling of very high emissions.

I took it for a diagnostics check at the local garage (Porsche) and the error messages that were coming up are, 1, O2 Sensor ouot of range, 2, Cyl 1 misfire, 3, Cyl 2 misfire, 4, Cyl 3 misfire.

The bloke at the garage send that it is not the o2 sensor that has broke, and it will only be one of the cylinder that is misfiring, but the computer registers the full bank as misfiring.

He said it could be something as simple as the spark plug, or it could be as major as weak compression.

It is due to go in Monday to try and find out the cause and which cylinder, however in the mean time over the weekend, if there any thing I can check for that might be causing the problem.

I would be grateful of any help

Many Thanks

Russ

There are multiple O2 sensors...definitely correct that problem first and then run the car and re-test.

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Oct 7, 2005 3:01:55 PM

RascalRuss: Newbie; Loc: UK; Posts: 8, Gallery; Registered on: Oct 6, 2005; Reply to: 964C2

Re: Boxster Misfire

I thought so, there are two is there??

The chap at the garage told the that the data suggests these are working correctly, and are going out of range due to the amount of unburnt fuel its pushing though.

When it was on the porsche software, both sensors were reading about 1 at idla (im not sure what the 1 stands for, ppm, percent??) Does this sound about right though.

What other fault can I look for and maybe check with a standard multimeter??

many thanks

Russ

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Oct 7, 2005 4:21:35 PM

964C2: Expert; Loc: Dallas, TX , United States; Posts: 1825, Gallery; Registered on: May 11, 2004; Reply to: RascalRuss

Re: Boxster Misfire

Quote:
RascalRuss said:
I thought so, there are two is there??

The chap at the garage told the that the data suggests these are working correctly, and are going out of range due to the amount of unburnt fuel its pushing though.

When it was on the porsche software, both sensors were reading about 1 at idla (im not sure what the 1 stands for, ppm, percent??) Does this sound about right though.

What other fault can I look for and maybe check with a standard multimeter??

many thanks

Russ

My understanding is that O2 sensors either work, or don't work correctly. It's not a matter of "going out of range" and then "going back" when another problem is corrected.
It would be worthwhile to get another mechanics opinion.

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Oct 7, 2005 7:36:21 PM

RascalRuss: Newbie; Loc: UK; Posts: 8, Gallery; Registered on: Oct 6, 2005; Reply to: 964C2

Re: Boxster Misfire

I see, will do that, thanks for the advice.#

Would faulty O2 sensors cause misfire though??

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Oct 7, 2005 8:06:48 PM

fritz: Rennteam VIP; Loc: BaWü , Germany; Posts: 10248, Gallery; Registered on: Jul 23, 2003; Reply to: RascalRuss

Re: Boxster Misfire

Quote:
RascalRuss said:
Hi All,

Wonder if some of you might be able to give me some help.

I have a Boxster 1998 2.5l, and the last couple of weeks its been drinking the fuel heavily, gaining alot of soot in the exhaust, and smelling of very high emissions.

I took it for a diagnostics check at the local garage (Porsche) and the error messages that were coming up are, 1, O2 Sensor ouot of range, 2, Cyl 1 misfire, 3, Cyl 2 misfire, 4, Cyl 3 misfire.

The bloke at the garage send that it is not the o2 sensor that has broke, and it will only be one of the cylinder that is misfiring, but the computer registers the full bank as misfiring.

He said it could be something as simple as the spark plug, or it could be as major as weak compression.

It is due to go in Monday to try and find out the cause and which cylinder, however in the mean time over the weekend, if there any thing I can check for that might be causing the problem.

I would be grateful of any help

Many Thanks

Russ

Russ,
Your car has 1 lambda (O2) sensor for each of the two "banks" of cylinders. If sensor goes "out of range" for one of the banks, meaning fuel/air mixture is not burning correctly before it gets to the sensor, then the usual cause would be a misfire of one or more of the 3 cylinders in that bank. In your case, a misfire in cylinders 1, 2 or 3. The diagnosis system has no way of telling which one it is.

As your techie suggested, the misfire could be caused by something simple like a plug, plug coil, or plug lead, or the misfire could be the result of lack of cnmpression due to a mechanical fault, like piston rings or valve leaking.

If your car was under warranty, I would have expected them to keep it in the shop and send you home in a "loaner". As it is, you shouldn't drive it more than you have to before it is fixed, 'cos it could compound the damage. I hope for your sake that you just need new plugs.

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Oct 7, 2005 8:29:24 PM

964C2: Expert; Loc: Dallas, TX , United States; Posts: 1825, Gallery; Registered on: May 11, 2004; Reply to: fritz

Re: Boxster Misfire

Quote:
fritz said:
Quote:
RascalRuss said:
Hi All,

Wonder if some of you might be able to give me some help.

I have a Boxster 1998 2.5l, and the last couple of weeks its been drinking the fuel heavily, gaining alot of soot in the exhaust, and smelling of very high emissions.

I took it for a diagnostics check at the local garage (Porsche) and the error messages that were coming up are, 1, O2 Sensor ouot of range, 2, Cyl 1 misfire, 3, Cyl 2 misfire, 4, Cyl 3 misfire.

The bloke at the garage send that it is not the o2 sensor that has broke, and it will only be one of the cylinder that is misfiring, but the computer registers the full bank as misfiring.

He said it could be something as simple as the spark plug, or it could be as major as weak compression.

It is due to go in Monday to try and find out the cause and which cylinder, however in the mean time over the weekend, if there any thing I can check for that might be causing the problem.

I would be grateful of any help

Many Thanks

Russ

Russ,
Your car has 1 lambda (O2) sensor for each of the two "banks" of cylinders. If sensor goes "out of range" for one of the banks, meaning fuel/air mixture is not burning correctly before it gets to the sensor, then the usual cause would be a misfire of one or more of the 3 cylinders in that bank. In your case, a misfire in cylinders 1, 2 or 3. The diagnosis system has no way of telling which one it is.

As your techie suggested, the misfire could be caused by something simple like a plug, plug coil, or plug lead, or the misfire could be the result of lack of cnmpression due to a mechanical fault, like piston rings or valve leaking.

If your car was under warranty, I would have expected them to keep it in the shop and send you home in a "loaner". As it is, you shouldn't drive it more than you have to before it is fixed, 'cos it could compound the damage. I hope for your sake that you just need new plugs.

Fritz, if the O2 sensor was actually bad, wouldn't it cause the DME to put that bank of cylinders into "limp home" mode and cause the car to run very rough??
964C2

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Oct 7, 2005 8:58:09 PM

fritz: Rennteam VIP; Loc: BaWü , Germany; Posts: 10248, Gallery; Registered on: Jul 23, 2003; Reply to: 964C2

Re: Boxster Misfire

Quote:
964C2 said:
Fritz, if the O2 sensor was actually bad, wouldn't it cause the DME to put that bank of cylinders into "limp home" mode and cause the car to run very rough??
964C2

Frankly, I don't know, but I would guess that:
- a completely failed lambda sensor would throw up a specific error message saying just that, instead of "cyls. 1 to 3 out of range"

- the DME would put the whole engine into "redundancy mode", and not just one bank of cylinders

- the redundancy program would be a "tame" one which would endeavor to allow the engine to run very smoothly despite suboptimal conditions, rather than roughly.

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Oct 7, 2005 9:31:51 PM

RascalRuss: Newbie; Loc: UK; Posts: 8, Gallery; Registered on: Oct 6, 2005; Reply to: fritz

Re: Boxster Misfire

Damn, you know your stuff.

I unfortunatly HAVE to drive about 200 miles in it tomorrow, and dont have any other choice, so with the risk of further damage, is it best to take it very easy and not try to throttle it about 2500 - 3000 RPM??

Also, are there any checks I can do in the morning, like clean the plugs, check the coils on a multi meter, etc.

Let me know and many thanks for your help

Russ

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Oct 7, 2005 9:42:27 PM

fritz: Rennteam VIP; Loc: BaWü , Germany; Posts: 10248, Gallery; Registered on: Jul 23, 2003; Reply to: RascalRuss

Re: Boxster Misfire

Quote:
RascalRuss said:
Damn, you know your stuff.

I unfortunatly HAVE to drive about 200 miles in it tomorrow, and dont have any other choice, so with the risk of further damage, is it best to take it very easy and not try to throttle it about 2500 - 3000 RPM??

Also, are there any checks I can do in the morning, like clean the plugs, check the coils on a multi meter, etc.

Let me know and many thanks for your help

Russ

Don't jump to the wrong conclusions! I did say I DIDN'T know and was guessing.

Cleaning plugs might even cure the problem, if you can get at them on the mid-engined Boxster. DON'T TRY TO CHECK THE COILS WITH A VOLTMETER! They produce about gadzillion volts!

Do you have a decently competent auto workshop in your neighbourhead which operates on a Saturday morning? Probably a rare thing these days, despite longer shopping hours than in the past here in Europe.

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Oct 7, 2005 10:41:41 PM

Rom: Newbie; Loc: Bay Area, CA; Posts: 7, Gallery; Registered on: Oct 6, 2005; Reply to: fritz

Re: Boxster Misfire

Take the spark plugs out and look at them (or get your mechanic to do so). Their general condition can be a helpful indicator of the problem. Spark plugs fail all the time, however usually that would cause one cylinder to misfire - not three. Perhaps an ignition issue - not sure if Porsche uses one or two ignition coils on these engines, or if they've gone to coilpacks?

I still haven't gotten my tech manuals for the M96 engine, so can't be more precise...

Thanks!

Shash

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Oct 7, 2005 10:52:28 PM

RascalRuss: Newbie; Loc: UK; Posts: 8, Gallery; Registered on: Oct 6, 2005; Reply to: Rom

Re: Boxster Misfire

Hi, Im a trained mechanic myself, but now work as a design engineer so know a fair bit about cars and love getting my hands dirty, so i will be doing as much work myself as i can.

Aswel as the spark plugs, are there any other things i can check??

Many thanks

Russ

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Oct 8, 2005 10:35:40 PM

fritz: Rennteam VIP; Loc: BaWü , Germany; Posts: 10248, Gallery; Registered on: Jul 23, 2003; Reply to: Rom

Re: Boxster Misfire

Quote:
Rom said:
Spark plugs fail all the time, however usually that would cause one cylinder to misfire - not three.

As I tried to explain above, the diagnosis system in this instance probably could only detect that one or more cylinders in a bank was misfiring, due to the so-called "out of range oxygen reading", so the error report could not be more specific than "Misfire cyls. 1, 2, 3", or words to that effect.

Quote:
Rom said:Perhaps an ignition issue - not sure if Porsche uses one or two ignition coils on these engines, or if they've gone to coilpacks?

The engines use one plug-top coil per cylinder.

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Oct 17, 2005 5:38:55 PM

964C2: Expert; Loc: Dallas, TX , United States; Posts: 1825, Gallery; Registered on: May 11, 2004; Reply to: RascalRuss

Re: Boxster Misfire

RascalRuss, did you ever solve your misfire problem?
964C2

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Oct 17, 2005 7:54:50 PM

fritz: Rennteam VIP; Loc: BaWü , Germany; Posts: 10248, Gallery; Registered on: Jul 23, 2003; Reply to: 964C2

Re: Boxster Misfire

Quote:
964C2 said:
RascalRuss, did you ever solve your misfire problem?
964C2

Guess he must have, and now he can't stop driving it.

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