Acceleration Hesitation
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Joined: Sep 2007
Posts: 92
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From: Johns Creek, GA
Acceleration Hesitation
OK drivetrain gurus. What would cause a slight hiccup in moderate acceleration at exactly 3400 rpm? Doesn't happen (or at least I can't feel it) when getting into the gas harder. Once through, smooth as silk to redline.
Racer
Joined: Apr 2008
Posts: 486
Likes: 0
From: Lexington, Kentucky
I would guess there is a problem with the tracks on the AFM if it hasn't been modified to MAF.
This may help:
http://www.the944.com/afm.htm
This may help:
http://www.the944.com/afm.htm
Drifting
Joined: Aug 2010
Posts: 2,654
Likes: 24
From: Orlando area
I've been chasing this problem since I acquired this car. I've replaced TPS, AFM, plugs, wires, cap, rotor, throttle body seals and repaired all the vacuum leaks and finally, today, I replaced the FPR with a new Bosch unit and it now seems that the issue is gone. I never actually associated it with a specific RPM number. I'll drive it a bit more to be sure, but it runs smooth now, even when the engine was cold, which it didn't previously.
Three Wheelin'
Joined: Jun 2010
Posts: 1,883
Likes: 67
From: Northern California, '86 951
Name that source:
"For years, 944 owners and even experienced Porsche mechanics, have on a regular basis replaced perfectly good DMEs, fuel pumps, and various other components because of faulty fuel pressure regulators (FPR). However, it's quite understandable as faulty FPRs can display a wide range of symptoms depending on how the regulator fails."
"For years, 944 owners and even experienced Porsche mechanics, have on a regular basis replaced perfectly good DMEs, fuel pumps, and various other components because of faulty fuel pressure regulators (FPR). However, it's quite understandable as faulty FPRs can display a wide range of symptoms depending on how the regulator fails."
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Racer
Joined: Aug 2013
Posts: 290
Likes: 1
From: Grass Valley
+1 vacuum lines.
Fixed my vacuum lines, and the hesitations in my acceleration were largely cleared up.
I'm replacing the fpr next, it leaks, and hoping that clears up a drop in idle when the throttle is released. That seems to be the only problem the vacuum line replacements didn't fix.
Fixed my vacuum lines, and the hesitations in my acceleration were largely cleared up.
I'm replacing the fpr next, it leaks, and hoping that clears up a drop in idle when the throttle is released. That seems to be the only problem the vacuum line replacements didn't fix.
Drifting
Joined: Aug 2010
Posts: 2,654
Likes: 24
From: Orlando area
I had hoped that this was the problem when I first lifted the hood to diagnose the issue. After that, I just progressively did the cheaper things first, since this isn't my DD.
Last edited by mytrplseven; Jul 9, 2014 at 11:52 AM.
Racer
Joined: Aug 2013
Posts: 290
Likes: 1
From: Grass Valley
Three Wheelin'
Joined: Jun 2010
Posts: 1,883
Likes: 67
From: Northern California, '86 951