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1983 Porsche 944 running rough and rich (Read 128 times)
Cole Thomas
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1983 Porsche 944 running rough and rich
Oct 30th, 2019 at 3:02pm
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I have a 1983 944 NA in sienna red and am having issues with it running rough. it had a few vacuum leaks that I just fixed. Before the leaks were fixed, I had to let it warm up for it to run right and then it still ran rich. Now that I have the vacuum leaks fixed it acts like it is misfiring and still runs rich. When I rev the engine it sounds very bad and sounds like it is misfiring. Even after it completely warms up I still have the issue. it only goes away if I rev it to about 3200 RPM. I am not sure how I could have made the issue worse. Honestly, it ran better with the vacuum leak that it had. Any responses would help. Thank you

Just might have figured out the issue. I just put in new spark plugs and it still ran rough. Then I unplugged the AFM and it ran better than it ever has since I have owned it. However, it dies after a couple seconds. I think this means that the AFM is bad. Is that a viable solution?
« Last Edit: Nov 1st, 2019 at 12:30am by Cole Thomas »  
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anchor
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Re: 1983 Porsche 944 running rough and rich
Reply #1 - Nov 1st, 2019 at 11:54am
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Popular concept the described symptons fix is the throttle body lnline with the AFM after secure vacuum which you have already worked.

You will find some shops good at these repairs. Clarks Garage has remedy papers as well other Porsche publications shop manuals.
One test is disconnect the oxygen sensor. It keeps the engine in open LAMBDA mode.

Eventually the temp sensor and switches referred to as TPS.
« Last Edit: Nov 1st, 2019 at 1:42pm by anchor »  

fuel-18.pdf ( 53 KB | 3 Downloads )

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Cole Thomas
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Re: 1983 Porsche 944 running rough and rich
Reply #2 - Nov 1st, 2019 at 3:01pm
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anchor wrote on Nov 1st, 2019 at 11:54am:
Popular concept the described symptons fix is the throttle body lnline with the AFM after secure vacuum which you have already worked.

You will find some shops good at these repairs. Clarks Garage has remedy papers as well other Porsche publications shop manuals.
One test is disconnect the oxygen sensor. It keeps the engine in open LAMBDA mode.

Eventually the temp sensor and switches referred to as TPS.


The oxygen sensor on my car was actually broken by the previous owner. Can I run it without one? I think I'm just going to clean the AFM and see if that makes a difference. As of right now with the AFM unplugged the car runs great for a second and then dies. With the AFM plugged in it runs terrible and Accelerates extremely slow and sounds like it is misfiring. Sounds like a bad lawnmower.
  
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anchor
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Re: 1983 Porsche 944 running rough and rich
Reply #3 - Nov 1st, 2019 at 4:06pm
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Well that is covered by the Clark's attached where some can and some cannot run.

If the temp and the TPS is good to go you could have too much back pressure from the LAMBDA or your cat convert cold be plugged or your DME could be not getting or producing the correct signals.

Best check this forum for more than one file. Piece by piece you will get there.
  

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Cole Thomas
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Re: 1983 Porsche 944 running rough and rich
Reply #4 - Nov 1st, 2019 at 6:43pm
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anchor wrote on Nov 1st, 2019 at 4:06pm:
Well that is covered by the Clark's attached where some can and some cannot run.

If the temp and the TPS is good to go you could have too much back pressure from the LAMBDA or your cat convert cold be plugged or your DME could be not getting or producing the correct signals.

Best check this forum for more than one file. Piece by piece you will get there.


Noted Thank you
  
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anchor
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Re: 1983 Porsche 944 running rough and rich
Reply #5 - Nov 1st, 2019 at 10:16pm
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They are other possibilities think packaged process fuel / air map chips may allow not running a cat as say for instance...maybe.
Common Catalytic Converter Problems reviewed 363 times from West Palm Beach Auto Repair might help?
Basically your post included misfire and stop gap to keep it running. A wild guess would include to much heat internal to the converter or deposits of exhaust mucking up the 944 engine management.
www.foreignaffairsauto.com

Thinking a little more to go on would be extra good instead of just replacing piece by piece.

Valve timing overlap, exhaust emissions , exhaust recirculation valve and intake manifold design are all contributors along with combustion chamber spark plug on power stroke might be a solution to control at desired RPM when at higher speeds.

« Last Edit: Nov 2nd, 2019 at 6:26pm by anchor »  

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Cole Thomas
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Re: 1983 Porsche 944 running rough and rich
Reply #6 - Nov 2nd, 2019 at 6:28pm
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anchor wrote on Nov 1st, 2019 at 10:16pm:
They are other possibilities think packaged process fuel / air map chips may allow not running a cat as say for instance...maybe.
Common Catalytic Converter Problems reviewed 363 times from West Palm Beach Auto Repair might help?
Basically your post included misfire and stop gap to keep it running. A wild guess would include to much heat internal to the converter or deposits of exhaust mucking up the 944 engine management.
www.foreignaffairsauto.com

Thinking a little more to go on would be extra good instead of just replacing piece by piece.

Valve timing overlap, exhaust emissions , exhaust recirculation valve and intake manifold design are all contributors along with combustion chamber spark plug on power stroke might be a solution to control at desired RPM when at higher speeds.



Thank you for the input. I am going to try and clean the AFM and then go from there.
  
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SactoJohn
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Re: 1983 Porsche 944 running rough and rich
Reply #7 - Nov 4th, 2019 at 12:52am
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Replace the AFM with a rebuilt one. Even if you did mess with the one that is on there and get it running better, it will never run as good as it would with a rebuilt one and sooner or later you will be fighting it. If the AFM has 100k+ miles on it, just replace it. They wear out. Even if your budget is tight, this is not the part to be penny pinching.
  
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Cole Thomas
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Re: 1983 Porsche 944 running rough and rich
Reply #8 - Nov 4th, 2019 at 4:37pm
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SactoJohn wrote on Nov 4th, 2019 at 12:52am:
Replace the AFM with a rebuilt one. Even if you did mess with the one that is on there and get it running better, it will never run as good as it would with a rebuilt one and sooner or later you will be fighting it. If the AFM has 100k+ miles on it, just replace it. They wear out. Even if your budget is tight, this is not the part to be penny pinching.


Thank you! Just ordered one. We'll see if it makes a difference. I tried cleaning mine and it did not make a difference. The car chugs really bad, hesitates, clouds of smoke when I drive it. I think the AFM is shot.
  
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