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GregD

Misfire / stutter and Check Engine Light - help!

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Hi,

Took my Boxster out of the garage for a drive this morning, after about 4 weeks of not moving it.

The car fired first time and seemed to run as normal for the first 6 or 7 miles, by which time it was fully warmed up.

Then suddenly, when accelerating from 30 mph out of a village at low-2000s rpm, the car was very hesitant and didn't want to gain rpm. It had a kind of stutter / misfire and after a couple of hundred yards the check engine light flashed on and off about 3 times then stayed on permanently.

I pulled over and the engine was sounding a little lumpy at idle, as well as smelling like it was running rich. I could get the engine to hold the revs constant at any speed above idle and the car sounded fine, but trying gain rpm resulted in the same misfiring behaviour. Turning the engine off and turning back on again had no effect on the condition and the CEL remained on.

A friend who had been driving behind me all the way said there had been no smoke or other tell tale signs from the exhaust.

I turned round and headed home, and the problem gradually subsided to the extent that by the time I was back on the driveway the car was running as normal, but the CEL remained on.

The car is a '99 2.5 manual with 86k. I've only owned it for about 3,500 miles, and although the car has been serviced at independents I'm not sure how well it has been maintained (last OPC stamp was at 48k).

I'm not really sure where to start with this - Can anyone help me?

Cheers,

Greg

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Maybe the car was homesick and just wanted to go home?

How old is the gas in the car, or how long has it been since you filled up? Is it in a heated garage? Sitting outside?

My initial guess would be you have gotten some water in the fuel tank, by condensation or from the last fill up. My guess is that there wasn't alot, but enough to get sucked up and burned, which explaines the rough running that cleared up. Any OBD reader should be able to check your engine codes, have them read then update the post, I'm sure someone can give you a good isea of where to go then. If all you get is misfire codes, clear them and see if they come back.

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I'm gonna presume

you know that CELs are backed up with diagnostic codes and that the first thing to do is to get access to a code reader and see what the codes tell you.

http://mike.focke.googlepages.com/acheckenginelight(cel)

That will lead you to more information and then an approach can be suggested.

Good luck.

Thanks for the advice guys. Looks like I need to get hold of an OBDII reader. I'll post back when I've got some codes.

Greg

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Ok - plugged in my shiny new reader and it's come up with a single code - P0306 - Cylinder 6 misfire.

I guess that could mean it's as simple as a dodgy spark plug or coil, but does anyone have any experience of other stuff that can trigger this sort of code?

Also please can someone tell me which cylinder is no. 6?

Thanks

Greg

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Ok - plugged in my shiny new reader and it's come up with a single code - P0306 - Cylinder 6 misfire.

I guess that could mean it's as simple as a dodgy spark plug or coil, but does anyone have any experience of other stuff that can trigger this sort of code?

Also please can someone tell me which cylinder is no. 6?

Thanks

Greg

The weird thing is: I just got back from autozone for a reading of the same P0306 code due to misfiring after I changed my spark plugs yesterday. I am now looking for info as to which cylinder is #6 as well!!!

Let us know if you do!

Mike

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Also please can someone tell me which cylinder is no. 6?

According to Sputter on 986forum.com the 6th is driverside (LHD cars) nearest to the rear bumper.

Mike

Sure enough, I replaced the spark-plug in cylinder six and all is well! the new plug I fitted a day prior was cracked... I must have done that without realizing!

Greg, I hope you will get your problem resolved. please keep us posted!

Mike

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I have a problem exactly like this and replaced the coil pack on 6

Now EVERYTIME I reset the ECU and drive from cold it does what you describe and comes up missfire on 6

I get the engine warm - reset again and drive and the problem never comes back

I suspect 6 is more prone to missfire when there are other issues

For a long term fix I'm looking at MAF cleaing or a possible oxygen sensor issue as i reset because it complains about oxygen sensor issues.

Now iirc I only see the oxygen sensor issues on Durametric - and ordinary ODBCII only shows 6 missfire code.

I also wonder if I am not following the reset proceedure which I beleive involves turning on the ignition for a minute without starting and turning it off again before starting the car

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