Dying above 5500 revs

[MikeO]

My 3.4 has a problem that's developing from intermittent to permanent in that it's losing virtually all acceleration above 6K revs and sometimes from as little as 5K. It seems worse under load (i.e. in 3rd rather than 2nd, or uphill). It was doing it intermittently, or it felt that given a few full bore sprints it would clear its' throat and sort itself out, and sometimes it will unclog itself somewhere between 6 and 7, or by backing off slightly and having another go, but to be honest I don't fancy keeping it in that area when there's clearly a problem, it sounds okay, but I don't know what damage I might be doing if e.g. it's starved of petrol.

I had a new air mass sensor fitted about 8K miles ago to clear a cough at about 4K revs, I'm wondering whether it's something sticking in the variocam (although it does sound okay to my untrained ear, and I remember a Porche technician saying that variocam problems are pretty obvious misfiring).

Any thoughts?

 

[Richard_Hamilton]

You really need to get it plugged into a PST2 or other scanner which will access the fault memory. Once you have a fault code it will make the diagnosis much easier.

 

[MikeO]

Yeah, except it had a service only about 3 weeks ago, and the diagnostic log didn't show any problems. Again I seem to remember someone saying that you need to do a "live" test with the engine running and wired up to the test equipment. I'm going to get it booked in the garage for next week

 

[Richard_Hamilton]

Mike,

If you are ever in the Maidenhead area with some spare time I would be happy to do a run with my scan tool to see if it flags up faults. email me via my Profile page if I can help.

 

[Guest]

I have exactly the same problem, and wrote about it on this forum some time ago. No faults show up on diagnostics, when tested. I am intrigued that a new MAF did not cure the problem, as I was contemplating giving it a try. If you do find out what is causing this problem, please let me know!

 

[Guest]

Have you had a DME check to see if there are any faults reported. It could be a faulty solenoid.

 

[oldtimer]

If you are also getting an intermittent misfire it might be the coils , think there's one per cylinder. I had to replace 2 on a 3.4 with 60k on the clock.

 

[MikeO]

Thanks for these thoughts guys. I'd forgotten I'd started this thread, as events moved on. As you will see from another thread soon afterwards I thought the engine had blown (clouds of oil smoke out the rear) but it turned out to be a failed oil seperator. Sorting that out also seems to have solved the power loss, so presumably there had been tiny amounts of oil getting in the engine for a while, scary thought, but seem to have got away without too much damage to the wallet (fingers crossed)