Loss of power problem - 964 turbo
 

Hi, all. I have a 1991 turbo that started exhibiting a weird problem.

When either driving or idling (generally idles around 800-900rpm), the car can start sputtering and loses power. If I watch the tach, it drops down to 400-500rpm. If I hit the gas, it sputters and struggles. The car lurches and cannot pick-up consistently. These episodes are intermittent and last anywhere from 5-15 seconds, at which point the car starts idling smoothly and all is well.

It's pretty unsafe to drive it like this, as I could lose power and get rear-ended. I took it to a local Porsche mechanic. He experienced it while driving, could watch it happen occasionally with the car idling in his lot, but it never lasted long enough for him to do any diagnosis. He had the car for 2 weeks and finally gave it back to me, saying "we need for it to fail for longer - I can't diagnose it the way it is and I don't just want to start replacing things without having an idea of what might be wrong."

Has anyone had any similar issue or good theories on how something like this could occur? Thanks in advance.

Check the turbo boards. I seem to recall the ez69 ignition causing intermittent problems like that...

What mods/engine management?

have him check the coil

I had similar problems on my 1989 3.3 turbo, was a vacuum leak.

Thanks, everyone. So far, I have the following culprits to potentially check

- flywheel sensor/connector
- EZ69 ignition
- ignition coil
- vacuum leak

you first have to make sure it is not fuel related. are your fuel pump relays ok, clogged fuel filters exhibit similar symptoms. Does your mechanic have a diagnostic tool that plugs in to the engine management? It was originally the hammer, but I think they are using more modern equipment.
When my coil went out, the car would just cut off at 4500, when my ez69 failed, it just wouldn't start. Pray it is not the ez69 as 3 years ago it was 3900.

The mechanic had the car for 2 weeks, during which time he experienced the problem during a drive and had the car running numerous times, heard it stumble and stutter, but it wouldn't last long enough for him to identify the cause. I don't know all of the things he might have done while he had the car, but I do believe he looked at the relays, tried to get a fuel pressure reading and other things. I don't recall him mentioning looking for a clogged fuel filter.

Maybe I need to take the car to a more electrically minded shop.

I never got this problem resolved and the car has just been sitting in my garage the past 3 months, unsafe to drive.

I pulled it out and let it idle in my driveway this weekend to see if I could catch the problem and get a video of it. It did happen and I got it on video (the car was already stumbling when the video starts and stumbles until the 54 second point, at which point, it corrects itself).

https://www.youtube.com/watch?v=9A3Xh5MALi8

Any theories on what this could be? Thanks in advance.

Sounds like an A/F ratio issue. Have you tried to disconnect the O2 sensor to see if it makes a difference?

Frank, you are much better off in the turbo forums.

911 / 930 Turbo & Super Charging Forum - Pelican Parts Technical BBS

Have you checked your boost hose from the turbo to the intercooler for leaks? That is a common problem with turbos. Good luck

I doubt it's the EZ69 or coil. My understanding is they work - or don't.
There isn't much electrical on this car - it has CIS just like the 930 - no "engine management" like on Motronic cars.

Did you or anybody do _anything_ to the engine prior to this happening? - obviously check any parts that have been recently touched.

Is this a recent and sudden change? If so I'd look hard at the vacuum/boost hoses. There aren't that many. Make sure the intercooler to throttle body o-ring is good - and yes the turbo to intercooler hose.

If it's been a slow process I'd look at fuel pressure (the WUR).

I also agree - post up on the Pelican 930 board - as well as Rennlist 964 Turbo specific.

My money is on leak or fuel pressure. Personally - I highly recommend the Brian Leask adjustable WUR.

Keep us posted