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Help! Seattle SC losing power and bogging down above 4k
Driving into work today, the SC seems a little rough...then, as she gets up to operating temp, she starts losing power and stumbling. Won't rev above 5k or so without bogging down. Hoping for the obvious, I pull/drift off the I-5 into a gas station, but all looks well with ignition/cap/visible vacuum lines, etc.
JW adjusted my valves about 10k ago, so I'm not sure if my initial gut reaction of "engine warming=valves tightening" applies, but I'm hoping for some input here. Car did start/run fine for a few minutes after sitting at gas station for 5 minutes (turned off), but then right back to crap after that.  John, you may have another car outside the shop later today.... 
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1984 928s 5 speed |
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02-27-2008, 06:13 AM
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JR |
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02-27-2008, 06:21 AM
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Indebted user
Join Date: Apr 2005
Location: Denver
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Damp???
(Sorry having just moved Seattle to CO I am a little smug  )
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"Trying to drive a 911 fast is like trying to throw a hammer backwards...." Unknown source 69 w/71 2.2L and Pretty Gulf paint! Past P Cars - 90 C4, 84 Carrera, 74 Coupe 2007 Toyota Tacoma 4dr TRD & 2005 BMW 1200GS |
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02-27-2008, 06:29 AM
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Dry as a bone, new wires/plugs/cap/rotor (not the problem, though...I've put plenty of miles on them already)
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1984 928s 5 speed |
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02-27-2008, 06:47 AM
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Was going to say the cat is bad/plugged, but now I see it's a '79 - no cat.
Doubt it's valves if that was done 10k mi ago... and if JW did the adjust, it's got to be good. Check fuel filter, plugged from a tank of dirty gas, maybe. Does it run ok again for awhile after you let it sit, then do it again? |
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02-27-2008, 08:12 AM
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It fired up ok after sitting overnight, and seemed only a little sluggish as I pulled onto the freeway at 4:45 am.
Seems like as it warmed up it ran worse and worse... Says Cat on the doorjamb sticker, but I'm embarrassed to say I never looked that closely at the exhaust... SHould've installed that new fuel filter I bought!
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1984 928s 5 speed |
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02-27-2008, 08:19 AM
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'80 was the first cat year... I think, but, if it says it has one on the doorjamb, hmmm... does it have an air pump - if not, it may have a cat, or not.
Look behind the the LR tire, big can thing w/ a wire thing coming out of it. May have a heat shield part way around it. If the wire thing comes out of something only a little bigger than the exhaust pipe, that's probably not a cat. Your symptoms could definitely be a plugged cat, and it can happen all of a sudden on an old cat. |
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02-27-2008, 08:27 AM
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This could be related to either a fuel system problem or an ignition system problem. I know you said you recently changed a bunch of ignition stuff but I've seen quite a few sets of bad wires, or plugs that weren't the correct ones for the engine that ran a few miles, then gave problems. In the time we have discussed this, this morning, JW could probably have diagnosed and fixed it... JR |
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02-27-2008, 08:27 AM
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Your '79 is smog exempt now, in Washington State. Get rid of that stock exhaust system and get heat exchangers that exit to the rear, into a "2-in" muffler. Whether they be old, early heat exchangers or expensive SSI's. This will make your engine breathe better.
The valve adjust is not the problem. Javadog is correct. Ignition is almost always the culprit, but if this thing is running good cold, and having severe problems only when warmed up, then I am suspicious about the fuel system. The part of the system that leans the mixture as temps rise. Warm up regulator. Auxilliary Air Valve. Etc.
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Man of Carbon Fiber (stronger than steel) Mocha 1978 911SC. "Coco" |
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02-27-2008, 08:27 AM
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I'm thinking cat pretty hard now. |
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02-27-2008, 08:55 AM
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OK, the cat's there...no wire, since it's a '79.
Can one visually check a cat for plugging once it's off? Then again, hell with it... gimme a bypass!
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02-27-2008, 08:57 AM
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Just talked to JW, thinks it may be fuel filter.
Easy check, and I've got a fresh one at home. Now to hobble it back up the freeway.....
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02-27-2008, 09:05 AM
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Please report if that fixed it.
GB |
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02-27-2008, 02:23 PM
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UPDATE: SC power loss fixed
Wow. What a difference $15 makes.....I should've changed that stupid Fram filter ages ago!
Runs better than ever, I think it was a slow degradation until it finally got plugged. Just got back from a screaming test drive, man I'm glad that was the problem. With a baby on the way, there isn't much room for a rebuild right now... Though I'm hooked on the cat bypass idea.  Thanks to all for your input, man I love this board! Eric
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02-27-2008, 05:15 PM
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If it's the filter - seems like it - you should check the tank if it happened suddenly. If there's junk in the tank from a bad load of gas, it will clog the new filter also before too long also. |
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02-27-2008, 06:38 PM
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I will def. check tank when I go to replace fuel sender.
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02-28-2008, 06:59 AM
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I'd like to make a suggestion. I don't know what filter you used but I'd highly recommend using the factory parts on these cars, and not the aftermarket stuff you can buy a the local parts houses. I did a little research years ago, cutting open various filters to see what your money actually bought and it's an apples and oranges thing. The cheap stuff (even many "brand names" that are well known in the US) often is essentially crap.
I buy from well known sources, too. Over the years I've seen a few things that I'd classify as Asian copies of the good stuff. Not a good thing. JR |
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02-28-2008, 07:11 AM
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Old filter was FLAPS Fram from PO.
New filter is Bosch, bought from our host. Made in Spain. Thought about cutting the old one open, but got tired of fooling with it. Problem solved, next........
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1984 928s 5 speed |
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02-28-2008, 07:26 AM
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