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Puzzling problem with 944S2

 
Old 05-19-2013, 03:59 PM
  #1  
marc181
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Default Puzzling problem with 944S2

I'm wondering if anyone can help me, I've had this problem with my '90 944S2 for years and have not been able to find a solution.

It's an intermitten problem but when it manifests, the car will stall when I step on the brakes to stop for a light or to slow the car for a turn. Some of the other symptoms include once the car is restarted, a major hesitation when I step on the accelerator, at this point the car is sputtering and bucking and the exhaust smells sour, then car will suddenly rush forward.

Over the years and with several different mechanics, I have changed:

fuel filter
had the DME replaced
throttle body replaced
air flow sensor replaced
timing sensor replaced

Each time I got the car back, it would run fine for several months maybe even a year before the problem came back. The last change was about 20 months ago when the timing sensor was replaced. I've already spent $3,000 this year to have the sunroof repaired and the steering rack replaced. Any advice would be greatly appreciated. Thanks in advance.

Marc
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Old 05-19-2013, 04:06 PM
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Jfrahm
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Bucking is often a cracked intake boot after the AFM, letting in unmetered air at times. The fuel pump could also be a problem, maybe tank debris also.
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Old 05-19-2013, 04:20 PM
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marc181
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Thanks for getting back to me. I thought about tank debris also. I wonder if the tank needs to be replaced, the car does sit for long stretches of time. Come to think of it, I believe the fuel pump was changed.

The cracked intake boot is interesting. I wonder if the mechanics I took the car to checked that.
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Old 05-19-2013, 05:02 PM
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Possible vacuum lines leaking or collapsed is something to check out. When hitting the brakes, you are using the vacuum of the engine along with your brake booster to give you brake assist. When hitting the brakes, you could be dumping the vacuum causing the car to run rough. Then it may take time to build up vacuum again. Do you notice the brake pedal hard to press during this problem? I've seen a similar problem with a hard brake pedal where it would go away for a few weeks but return. The fix was a new vacuum line kit. The kit is a good upgrade to perform as regular maintenance as well.

Hope this helps.
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Old 05-19-2013, 05:05 PM
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It sounds like a vacuum issues. When did you last change the lines? Rubber goes bad over time and it might just be you have a leak that only shows at certain times like when the line gets hot or touches something. If it happens when you brake I would start at the brake vacuum line, especially at the vacuum check valve on the brake booster and work forward from there. WYIT I would change all vacuum lines to silicone as a precaution, probably due anyway.
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Old 05-19-2013, 05:24 PM
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The car has had vacuum tests but to your point, at 23 years old, perhaps there is a hidden failure somewhere that "hides" during the tests. Since the problem is intermitten, and the problems are happening now, my concern is that soon there will be a complete failure that will leave me stranded. To add insult to injury, the clutch pedal has been inconsistent, falling to the floor and not rebounding. I think there's a hydraulic issue there and I would guess the clutch needs replacing.
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Old 05-19-2013, 07:46 PM
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Before I replaced the clutch I would replace the clutch master and slave, these do not require replacement of the clutch.
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Old 05-19-2013, 07:59 PM
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I love the car and I've owned it for 16 years but I'm concerned that there are a lot of (expensive) gremlins to chase down.
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Old 05-19-2013, 08:32 PM
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for the clutch check the slave and master.... bleed the clutch if necessary. Mine was doing the same thing just recently found a coupler leaking so I tightened it now I need to bleed the system again but the clutch works just a little soft up top.
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Old 05-20-2013, 04:43 AM
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Is the problem caused by slowing down, or by hitting the brake pedal? I.e., does it happen if you use the engine to slow down? I wouldn't recommend disconnecting your brake pedal switch, but it would be a good way to see if the problem is electrical in nature.
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Old 05-20-2013, 06:00 AM
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mikey_audiogeek
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Originally Posted by marc181 View Post
I love the car and I've owned it for 16 years but I'm concerned that there are a lot of (expensive) gremlins to chase down.
If you love the car and you have owned it for 16 years then there WON'T be a lot of expensive gremlins to chase down. You don't have any previous owner issues to resolve...

Cheers,
Mike
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Old 05-20-2013, 01:40 PM
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The problem has been happening slowing down or when I come to a complete stop.
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Old 05-20-2013, 01:42 PM
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Mike, I hope you're right about the expensive gremlins but I think the clutch needs to be replaced, I found out the car has an electrical leak in January and I was informed the whole brake system needs to be replaced. Now, this intermitten vacuum/stuttering problem has reappeared. Not to mention the $3,000 I spent in January.
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