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Porsche Crest Idle jumping up 200,400 rpms, wires or Permatune CDI problem

Strange thing, for a couple of years now I've been getting this odd idle jump,its not hunting, let me try to explain the best I can, When I start the car it runs fine and idle great, the problem starts after i drive for awhile, when I come to a stop light the idle jumps up from normal idle 200 to 400 rpms with a small violent jump, and lately when the idle jumps it seems to be dieseling as it comes down, it does it, maybe once or twice a drive.

I have checked an rechecked the fuel system and vacuum hoses and intercooler connections, all that stuff looks good,

I have also replaced the spark plugs, The wires are old , from 1999 about 60.000 miles , I have already ordered a set from our host , if that doesn't fix the problem ,I'll have to check my Permatune CDI with built in coil, I may have to replace that also and that not cheap, right now it just a guessing game, it would be good if I had a stock CDI and coil to test with, before i buy a new one.

Can anyone shed some light on the this problem,

thanks
Helio

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Last edited by heliolps2; 05-15-2012 at 05:43 PM..
Old 05-15-2012, 04:48 PM
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Vacuum advance pot on distributor having issues, actuator rod attached to pot diaphram hanging up due to corrosion? Advance plates in distributor hanging up?

Mark
Old 05-16-2012, 08:17 AM
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Ok ,I replaced the spark plug wires, it did not change a thing , I also disconnected the vacuum hoses at the Dizzy no change, I check the Dizzy for play and there seems to be alot of play, I would say about 1/8 of an inch,

Could this be the problem ?
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1986 944 turbo -first car
1997 993 Cab 6 speed-sold
1992 964 C2 turbo
SOLD, 911GT ,CIS, 428 fwhp 450 trq, Carrillo rods, 964 cams, TT retainers,7.5 comp 1.1 bar boost 320 ml black fuel head 009 injectors, 044 pumps, 60-1 T4/T3 dual scroll turbo
Old 05-20-2012, 05:16 AM
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Put a timing light on it. If it's the distributor the timing mark will jump forward and back as the idle speed changes.

If the distributor play you're noticing is rotational play of the rotor that springs back when you release it your stretching the centrifical advance weight springs and thats normal.

If it's axial or up and down play of the distributor shaft it's probably the fiber shim on the distributor shaft under the centrifical advance plate has gone away. They all do after time and alot of miles.
The shim under the distributor gear may be worn too. There is also a screw under the dust seal in the distributor shaft below the rotor that should be tight.

If it's lateral or sideways play of the distributor shaft the distributor probably needs to be rebuilt with new bushings or replaced.
Old 05-20-2012, 11:19 AM
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Thanks,
The shaft play is up and down, and when I put the timing light on it, the timing jumps back and forward a little, and the rpms also jump a little, I guess its time for a rebuild ? how much does this cost and where do I go,
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1986 944 turbo -first car
1997 993 Cab 6 speed-sold
1992 964 C2 turbo
SOLD, 911GT ,CIS, 428 fwhp 450 trq, Carrillo rods, 964 cams, TT retainers,7.5 comp 1.1 bar boost 320 ml black fuel head 009 injectors, 044 pumps, 60-1 T4/T3 dual scroll turbo
Old 05-21-2012, 03:35 PM
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Up date,

I replaced the old Permatune with Permatune's new CDI, Problem solved, My old unit was the old coil and CDI in one from the 90's, Peramtune was nice enough to replace it with their new coil and CDI that looks like the original Porsche box for FREE , WOW what great service,
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1986 944 turbo -first car
1997 993 Cab 6 speed-sold
1992 964 C2 turbo
SOLD, 911GT ,CIS, 428 fwhp 450 trq, Carrillo rods, 964 cams, TT retainers,7.5 comp 1.1 bar boost 320 ml black fuel head 009 injectors, 044 pumps, 60-1 T4/T3 dual scroll turbo
Old 05-22-2013, 10:53 AM
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Quote:
Originally Posted by heliolps2 View Post
Up date,

I replaced the old Permatune with Permatune's new CDI, Problem solved, My old unit was the old coil and CDI in one from the 90's, Peramtune was nice enough to replace it with their new coil and CDI that looks like the original Porsche box for FREE , WOW what great service,
Wow is right! Was the Permatune fairly new, so they covered it like 'under warranty', or just being nice guys? Hope MSD does the same for me should mine ever fail.
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Old 05-22-2013, 12:14 PM
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the first one wwas bought in 1999 and again a replacement in 2003, the second one lasted 10 years, nice guys for sure.

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1986 944 turbo -first car
1997 993 Cab 6 speed-sold
1992 964 C2 turbo
SOLD, 911GT ,CIS, 428 fwhp 450 trq, Carrillo rods, 964 cams, TT retainers,7.5 comp 1.1 bar boost 320 ml black fuel head 009 injectors, 044 pumps, 60-1 T4/T3 dual scroll turbo
Old 05-22-2013, 12:52 PM
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