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Join Date: Oct 2005
Location: Lafayette, Louisiana
Posts: 622
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black smoke - causes?
I've been fighting a rough idle. After all my tests and a new DME relay things seem to be back to normal. However, after test driving around a while i pulled back into the garage, popped the hood and blipped the throttle. Real quick blips. Under 2500 rpm nothing, but if blip it to say 2500 - 3000+ rpm i get a light puff of black smoke. I figure this means Im running rich, but what culprits could be to blame.
Know this, my idle mixture, idle speed is out of wack and i will be addressing that soon. Would a out of spec idle mix setting cause this? I have new O2, CHT (2 wire), plugs, plug wires, rotor cap, DME, clean air cleaner.
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1986 944 Turbo - Guards Red |
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04-06-2006, 03:40 PM
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Make sure you are not low on oil.
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1977 911S Targa 2.7L (CIS) Silver/Black 2012 Infiniti G37X Coupe (AWD) 3.7L Black on Black 1989 modified Scat II HP Hovercraft George, Architect |
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04-06-2006, 03:55 PM
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Join Date: Mar 2002
Posts: 3,563
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Air Mlow Meter or fuel pressure regulator (or damper)?
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Merv '89 911 Turbo Cab Protomotive MAP ECU, Twin Plugged Heads, GT2-EVO CAMs, 3.3L fully finned P&C's, ARP fasteners, C2T head gaskets, Titanium Retainers, Turbo spec valves, springs & guides, 964 splash valves, GT35R BB turbo, GSF Stainless Headers, Magnaflow Exhaust, Full bay Intercooler, TiAL 46mm w/gate, TiAL 50mm BOV, Apexi AVC-R EBC, SPEC Stage3+ Clutch kit, Crane CDI Ignition 
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04-06-2006, 04:05 PM
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Location: Lafayette, Louisiana
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Quote:
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1986 944 Turbo - Guards Red |
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04-06-2006, 04:24 PM
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Join Date: Feb 2005
Location: Lancaster, uk
Posts: 191
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Bad idle. check the air bypass valve that bypasses around the front of the throttle body, they are notorious for going lazy.
take it off, clean it out, also check your vacuum pipes around the back of the throttle body, they are only small and can get full of oil gunk over the years. When you put the bypass valve back on, their is a trick to resetting it, you take a feed from a fuse on the sidewall and power it manually to reset the internals (I cant remember how but someone on here should know). My 3.2 had all the same symptoms - sorting the bypass sorted out 99% of them including the smoke since it ran v rich without the bypass working. Its the sort of thing that when you are cruising on tiny throttle movements the car is very jerky as the bypass doesnt allow it to breathe properly with the throttle plate shut - when working it will transfom the drive. just thought I would mention it as it is easy to check. |
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04-07-2006, 02:51 AM
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Location: Lafayette, Louisiana
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Quote:
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1986 944 Turbo - Guards Red |
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04-07-2006, 04:14 AM
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Location: Lancaster, uk
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I did that first time round,
the trick was done by someone who explained it thoroughly - and I completely missed what he was doing. All I can say is he took a feed from the sidewall fuseboard and seemed to connect to the valve. the motor whirred and the valve reset right back. Thats all I can say im afraid i wished id paid more attention. We also checked out the microswitch on the 'throttle closed' contact that triggers the bypass valve. |
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04-07-2006, 04:29 AM
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1977 Porsche 911S 2.7L
