intermittent rhythmic power loss
Thread Starter
Rennlist Member
Joined: Dec 2010
Posts: 1,972
Likes: 19
From: Morehead City NC
intermittent rhythmic power loss
I drove the 928 today on a few hour trip to pic up the wife's christmas present.
When i got on it it was "surging" as it accellerated.
here is a little history..
this summer i noticed a sudden power loss of a few hundred rpms as the car got close to redline... it would fall off then come back on the power.
The next symptom i had was that when it dropped down and the revs jumped up, there was a hesitation in the power, then it would surge back up and be fine.
today was much more pronounced... it had the recently consistent near red line hesitation... but something new started happening....
as the rpms increased in third climbing from 80-120 the car would rythmically loose power and rpm, then pick back up.. there was a consistant rythem to this "surging".
It was a quick loss of power but not abrupt like an ignition cutout... almost seemed like a fuel delivery issue.... could this be a bad fuel dampener, etc?
When i got on it it was "surging" as it accellerated.
here is a little history..
this summer i noticed a sudden power loss of a few hundred rpms as the car got close to redline... it would fall off then come back on the power.
The next symptom i had was that when it dropped down and the revs jumped up, there was a hesitation in the power, then it would surge back up and be fine.
today was much more pronounced... it had the recently consistent near red line hesitation... but something new started happening....
as the rpms increased in third climbing from 80-120 the car would rythmically loose power and rpm, then pick back up.. there was a consistant rythem to this "surging".
It was a quick loss of power but not abrupt like an ignition cutout... almost seemed like a fuel delivery issue.... could this be a bad fuel dampener, etc?
Rennlist Member
Joined: May 2003
Posts: 8,706
Likes: 153
From: Frankenmuth, Michigan
Fuel delivery rate okay? Fuel pressure regulator holds air under vacuum?
Thread Starter
Rennlist Member
Joined: Dec 2010
Posts: 1,972
Likes: 19
From: Morehead City NC
the hall and knock were done just before i bought the car by smith motorworks... a reputable shop....
not sure about the fuel pressure.. have a gauge and vac pump.... how do i test it?
not sure about the fuel pressure.. have a gauge and vac pump.... how do i test it?
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Three Wheelin'
Joined: Apr 2010
Posts: 1,295
Likes: 1
From: Virginia Beach, VA
Do the drops in power have an immediacy, a mechanical feel, or a slow rise and fall in power?
My oxygen sensor connector was shorting and dumping the signal to ground causing the computer to go in and out of closed loop. The effect was dramatic, and felt mechanical, immediate, and was more noticeable when pushing the revs higher in the lower gears.
Three Wheelin'
Joined: Apr 2010
Posts: 1,295
Likes: 1
From: Virginia Beach, VA
I actually am thinking about this backward. When the ECU goes into open loop, you will feel an increase in power because the air/fuel mix will suddenly turn rich, and economy will drop.
You're experienced loss of power, the opposite of what I was referring to. Sorry.
It does sound like you have some resistance occurring to either the fuel pressure or air flow.
You're experienced loss of power, the opposite of what I was referring to. Sorry.
It does sound like you have some resistance occurring to either the fuel pressure or air flow.
