Hard-Drive

First time poster here from the UK. I've just got my 2002 986 2.7 back on the road after 2 years off it. Lots of work...new steering rack, brake pipes all round...and more!

However I have a problem with a misfire. I pulled all the plugs and cleaned them, although they are just over 2 years old, and due to lack of use when the car was laid up, have done a few thousand miles maximum. They were obviously very clean anyway. I inspected the coil packs and they all look good too...no cracks. The car then ran fine for about a mile, and then the misfire was back...gah!

I have 3 CEL lights...

P1117
P0140
P1276

...but these are just O2 sensor related and should not be the cause of a pretty serious misfire. I've taken the plenum/throttle body off and cleaned it. I've not yet cleaned the MAF, but unplugging it made no difference.

The misfire is pretty bad...it's obvious at tickover, and worst on a heavy throttle under 3000rpm.

I'm thinking it must be coil packs, and I was going to disconnect each one with the engine running and see if there was one that did not make things worse! Can I do this without zapping myself...I assume the plugs that connect onto the coil packs are LT anyway.

Any other ideas?

Anker

What about the petrol in the tank. Did you add stabilizer? If not, your problem is gunk in the fuel that's blocking the injectors. If this really is the case I suggest you siphon all the fuel out of the tank, fill it up with new fuel and then add fuel injector cleaner. Worst case you will have to clean out the tank, which is a PITA.

Macster

Stale, really stale, fuel has to be considered. I do not believe at this stage adding stabilizer will rejuvenate the fuel. If it is bad enough to account for the misfires it is not advisable to drive the car and burn the fuel thus removing the stale fuel is advisable.

Since you just bought the car I'd advise you to not bother cleaning the plugs. They should not need cleaning. Since I gave up my dirt bikes I treat plugs as an install once item. If for any reason I believe plugs need to be removed I remove them and replace them. Might add since my dirt bike days I have not had any need to remove any plug from any car engine except when it is time to replace them either on miles or time.

Suggest you buy factory plugs: These come with an extended tip which helps keep the plug clean under low RPM operation yet exposes the tip to the cooler incoming intake air charge during high RPM operation.

At the same time you replace the plugs I'd recommend you replace the coils. Early on in my 2002 Boxster experience I learned from my visits to UK Boxster forums coils in Boxsters in the UK have a rather short life span.

Do not use anti-seize on the new plugs. This is unnecessary, interferes with heat transfer between the plug and head, and can foul O2 sensors. The factory plugs come with a dry flaky surface finish that is designed to not bias the tightening torque and allow good heat transfer and does not put the O2 sensors at risk. I replaced the plugs in my 2002 Boxster (and 2003 Turbo) a number of times at the scheduled miles and not once did the engine exhibit any improvement with the new plugs.

This is actually good news. It shows the plugs even in the case of the Boxster after 60K miles are still functioning quite well. The idea is to replace them *before* they go off, not after the engine is sputtering and acting up.