2000 996 3.4 Misfire below 2000rpm

[Damien675]

Hello

My 996 3.4 has developed a misfire on one of the right bank cylinders, it only happens between idle and 2000rpm. Below 2000rpm if I accelerate hard the engine feels very lumpy/hesitant though I rarely get the check engine light flashing. Above 2000rpm the engine is sweet.

I have replaced the ignition coils (BERU ones) but it has not made any difference. However I did notice that the rubber boot that fits over the ignition coil elect plug on cylinder 6 is badly split and I am concerned that this has degraded/corroded the contacts???

Any ideas?? Is this part of the engine loom easy to replace/repair????

 

[C2dweller]

It sounds like you might have a Variocam actuator failure. This would exhibit these symptoms.
It normally sticks and causes poor running at low or high rpm, depending on where it sticks.
Diagnostic check will help. You can manually check it too.
It's quite a job to replace, requiring exhaust and cam cover removal.
kr Lee

 

[Damien675]

Thanks for the advice I have booked it in with my local specialist to get it checked out.

On a related matter I when I replaced my ignition coils with Part no 99760210700 they are a different shape from my old ones and were delivered with new bolts to fit them with. However my original ignition coil heatshield does not seem to fit very well and is badly corroded. I have seen 997 version that seems a better shape, will it fit my 996???

Thanks again Lee

 

[C2dweller]

The bigger coil packs are the newer type. New covers are readily available and quite cheap.

Hope it goes well. Cheers

 

[devans]

I had similar issues some years back. found it was the variocam. investigated a possible diy but soon became evident it was a garage job. covers for ignition coils sell for around £27 each.

 

[Damien675]

Well looks like I may not have dodgy Variocam Soleniod, took car out today and check engine light came on, put car back on drive and re-checked all my coil plugs, furthest back coil on LH side of engine by the coolant overflow came off the moment I touched it. Checked all the others all good. Car now drives back at its amazing best. Clearly finger trouble!!!

On the downside I did notice my exhaust silencer box seems are starting to fall apart, looks like I need to find some nice shiny new ones.

Thanks to Lee and Devans for your help.