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99 Boxster engine misfire when starting cold


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Hi all,

My 1999 Boxster is having a problem of the engine misfire when I start the car first time in the morning especially when it's

cold or it sits for a few days. There was no check engine light. After I drove the car just for a few minutes, then it ran very smooth and

there was no longer the misfire. The engine ran whole day without misfiring until the next morning when I start the car again.

I replaced all the coil packs and the spark plugs and that doesn't fix the problem.

What might be the cause of the misfiring?

I appreciate your help.

Steve

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This is common, my wife's Boxster does the same thing. I find if I let it run 5 minutes or so before driving off, it minimizes the popping which sometimes will trigger a fault code and cause the CEL to come on.

I don't think anything is actually wrong with the car. Drive it gently until it warms a bit.

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Yes it is a problem and its not normal for a misfire - You need the fault code, however an air leak in the induction will give a very lean mixture and this can cause a misfire, a fault MAF will do the same as this measures air temperature and flow rate to calculate the mixture.

There is also an engine temperature sensor which sends a signal to the management system to assist the calculation of mixture ratio.

I believe the misfire to be a weak mixture but damp and other factors could be the cause - you really need the code

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I've had the same problem (especially during our unstable winter temperatures that fluctuate alot) and a small can of gas condensation remover (i have no idea what the product might be named where you are) fixed it. I usually fill one of these small bottles in my gasoline tank at every 3-4 fillups just to be sure.

Without it my engine sometimes does not run properly when it is cold, and it has also misfired once. So get yourself a small bottle of gas moisture remover or whatever it is named where you are and pour it in the tank :)

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  • 2 weeks later...

Adding a bottle of "water removal" to the full tank of gas does fix the problem.

My boxster is running very well without misfiring even after it sat in the garage for 10 days.

I want everyone to know this before they waste a lot of money on uncessary repairs.

Steve

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I think the problem remains- I dont believe that moisture in the tank is causing this as it would also be apparent when the car is warmed up.

You have a problem with a misfire and that problem will cost you dearly if you ignore it and hey presto magic bottles of formula will not sort the problem out, get the fault codes read.

If your problem was normal and magic bottles corrected it then we would all need the bottle too - and we dont

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The problem is that there is no fault code. I use the OPB-II scanner and it's clean.

You need to use a scanning tool that is capable of showing pending codes and all codes at the same time. Like Durametric, Porsche PST2 or Porsche PSWIS tester.

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  • 4 weeks later...

Hi all,

Just want to update what's going on with the engine misfiring of my 99 Boxster.

It's not normal. Eventually I got the cel code P1126.

It's the air/oil separator. I replaced it and all the misfiring and smoke went away.

Thanks for all the wonderful help from all of you.

Steve

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  • 3 weeks later...

Hey gang,

I have experienced similar problems with my 2000 Boxster. When the ambient temperature drops below about 50F degrees and I start the engine the first thing in the morning the engine will backfire and pop for about 15-20 seconds and then run normal. The acceleration is impacted as well until the engine is warm. I have to wait for about two or three minutes before the engine will cooperate and run normal. I ran the diagnostic check and the code reads P1126 . My question is where do you go from here? My manual offers no further diagnosis of the true problem so I will know what to replace or what device is actually malfunctioning.

A second issue I have is the automatic lowering of the passenger window when the door handle is raised. Can anyone advise the location of the proper switch?...and where to find a replacement?

Your help will be greatly appreciated.

Thanks

Barry G

Edited by capmot24@yahoo.com
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  • 2 weeks later...
Hi all,

Just want to update what's going on with the engine misfiring of my 99 Boxster.

It's not normal. Eventually I got the cel code P1126.

It's the air/oil separator. I replaced it and all the misfiring and smoke went away.

Thanks for all the wonderful help from all of you.

Steve

Hey Steve,

I have a similar problem with my Boxster. Where did you pick up the air/oil separator and how do you replace it?

Thanks

Barry G

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Hi all,

Just want to update what's going on with the engine misfiring of my 99 Boxster.

It's not normal. Eventually I got the cel code P1126.

It's the air/oil separator. I replaced it and all the misfiring and smoke went away.

Thanks for all the wonderful help from all of you.

Steve

Hey Steve,

I have a similar problem with my Boxster. Where did you pick up the air/oil separator and how do you replace it?

Thanks

Barry G

Hi Barry,

I bought the air/oil separator from partsgeek.com, it's $90.00. I have my friend install

for me. He is a mechanic and charged me $170.00.

I did a lot of research trying to figure out how to do it myself, then I finally gave up because I didn't think I could do

it myself.

Steve

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