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Running on 5 cylinders
My car was running perfectly yesterday. The motor was rebuilt recently. Plugs wires, distributor cap and rotor are new. I disconnected and reconnected 1 or 2 plug wires. I could feel them snap in place. Now the motor is running on 5 cylinders. I've checked the plug connectors. They are all tight. How can I figure out which cylinder is causing the problem?
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John Original owner '81 911SC blackmetallic coupe. Terbatrol, SSI, M+K Gen 4, SC+ cams, A/C delete, console delete, heater backdate, 7 & 8 x 16 Fuchs with polished rims, Turbo tie rods, tensioner update, Rennline engine mount bar, Mainely Custom sump plate, new top-end, corner balance. |
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04-21-2007, 04:22 PM
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Got two wires crossed? Recheck firing order.
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04-21-2007, 04:28 PM
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Never had two wires off at the same time.
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John Original owner '81 911SC blackmetallic coupe. Terbatrol, SSI, M+K Gen 4, SC+ cams, A/C delete, console delete, heater backdate, 7 & 8 x 16 Fuchs with polished rims, Turbo tie rods, tensioner update, Rennline engine mount bar, Mainely Custom sump plate, new top-end, corner balance. |
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04-21-2007, 04:34 PM
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Easiest thing to check though a long shot is for a defect in the cap at one of the terminals
Any chance you broke a spark plug on install? I'd suspect them then a bad wire. Real pain, isn't it - especially on one of these... pull all plugs and look for the one covered in fuel, swap in another plug and see if it changes. Make sure you have a good insulator in your plug socket. I busted off a brand new Delco plug recently in one of my other cars, must have been bad-in-box. |
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04-21-2007, 04:43 PM
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If it's the plug, I think I know which one. I'll pull it tomorrow & take a look.
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John Original owner '81 911SC blackmetallic coupe. Terbatrol, SSI, M+K Gen 4, SC+ cams, A/C delete, console delete, heater backdate, 7 & 8 x 16 Fuchs with polished rims, Turbo tie rods, tensioner update, Rennline engine mount bar, Mainely Custom sump plate, new top-end, corner balance. |
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04-21-2007, 04:58 PM
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Took off plug wires one by one. Resistance varies from 1+ to 7+ ohms from the shortest wire to the longest (these are Magnecor 2.5). Is this normal? The plugs have only been in the car for about 350 miles. No reason to suspect them. I checked one, and it looks perfect. Checked dizzy cap & rotor. Both 350 miles old & perfect. How would I know if my airbox is cracked? How could I check to see if it's a fuel problem. Definitely feels like one cylinder is not firing. If I rev the engine, it is not smooth or torquey.
More suggestions from the experts please!
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John Original owner '81 911SC blackmetallic coupe. Terbatrol, SSI, M+K Gen 4, SC+ cams, A/C delete, console delete, heater backdate, 7 & 8 x 16 Fuchs with polished rims, Turbo tie rods, tensioner update, Rennline engine mount bar, Mainely Custom sump plate, new top-end, corner balance. |
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04-22-2007, 10:35 AM
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My engine suddenly felt like it was running on 5 cylinders. Idle was OK, but no power. Pulled plugs and found one wet. Electrode was shorted by a piece of black who knows what. Cleaned up and reinstalled. Runs great.
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04-22-2007, 10:48 AM
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In a dark garage, run the car while looking at all plugs. Look for any flashing in the engine bay. I still think you broke one on install if car was OK before.
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04-22-2007, 12:03 PM
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Quote:
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John Original owner '81 911SC blackmetallic coupe. Terbatrol, SSI, M+K Gen 4, SC+ cams, A/C delete, console delete, heater backdate, 7 & 8 x 16 Fuchs with polished rims, Turbo tie rods, tensioner update, Rennline engine mount bar, Mainely Custom sump plate, new top-end, corner balance. |
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04-22-2007, 07:28 PM
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You said you put plugs in.
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04-22-2007, 07:39 PM
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You'd need to be pretty careless to break a spark plug when installing them, unless of course you dropped one on the concrete before installing it?
 Make sure ALL your leads have clicked onto the plug's (or dizzy's) terminal reliably and real tight. Double check them to make 100% sure they are nice and secure.
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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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04-22-2007, 09:14 PM
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I've done it with the best of tools. Sometimes they are broken in the box and just need a little extra 'help' to snap off. You'd be surprised.
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04-23-2007, 02:40 AM
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Quote:
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John Original owner '81 911SC blackmetallic coupe. Terbatrol, SSI, M+K Gen 4, SC+ cams, A/C delete, console delete, heater backdate, 7 & 8 x 16 Fuchs with polished rims, Turbo tie rods, tensioner update, Rennline engine mount bar, Mainely Custom sump plate, new top-end, corner balance. |
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04-23-2007, 04:12 AM
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Designer King
Join Date: Mar 2004
Location: Toronto, ON Canada
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One check you might try is to idle the engine. Have someone hold the throttle slightly open if you need to. Pull each plug wire off in turn. If you are indeed running on 5, the "bad" one is shown when the engine does not change when the plug is pulled.
Does this occur when the engine is cold or warm? Have you checked your fuel and control pressures and the WUR? It is probably plug/wire caused but may be coincidental.
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Paul Yellow 77 Sunroof Coupe/cork interior; 3.2L SS '80 engine/10.3:1/No O2; Carrera Tensioners; 11 Blade Fan; Turbo tie rods; Bilstein B6; 28 tube Cooler; SSI, Dansk; MSD/Blaster; 16x7" Fuchs/205/50 Firestone Firehawk Indy 500s; PCA/UCR, MID9 Never leave well enough alone |
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04-23-2007, 07:03 AM
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One thing I did notice. I backdated the heater recently and neglected to tighten the bracket that the coil sits on. There is a ground wire attached to this bracket. It is tight now, but if it was loose, could it have caused any damage to anything.
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John Original owner '81 911SC blackmetallic coupe. Terbatrol, SSI, M+K Gen 4, SC+ cams, A/C delete, console delete, heater backdate, 7 & 8 x 16 Fuchs with polished rims, Turbo tie rods, tensioner update, Rennline engine mount bar, Mainely Custom sump plate, new top-end, corner balance. |
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04-23-2007, 07:59 AM
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[QUOTE]Originally posted by Paulporsche
[B]One check you might try is to idle the engine. Have someone hold the throttle slightly open if you need to. Pull each plug wire off in turn. If you are indeed running on 5, the "bad" one is shown when the engine does not change when the plug is pulled. Safety question: Is it safe to pull and plug these in with the motor running?
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John Original owner '81 911SC blackmetallic coupe. Terbatrol, SSI, M+K Gen 4, SC+ cams, A/C delete, console delete, heater backdate, 7 & 8 x 16 Fuchs with polished rims, Turbo tie rods, tensioner update, Rennline engine mount bar, Mainely Custom sump plate, new top-end, corner balance. |
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04-23-2007, 08:02 AM
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[QUOTE]Originally posted by rs6er
[B] Quote:
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2021 Model Y 2005 Cayenne Turbo 2012 Panamera 4S 1980 911 SC 1999 996 Cab |
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04-23-2007, 08:45 AM
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[QUOTE]Originally posted by rs6er
[B] Quote:
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2021 Model Y 2005 Cayenne Turbo 2012 Panamera 4S 1980 911 SC 1999 996 Cab |
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04-23-2007, 08:55 AM
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[QUOTE]Originally posted by rs6er
[B] Quote:
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2021 Model Y 2005 Cayenne Turbo 2012 Panamera 4S 1980 911 SC 1999 996 Cab |
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04-23-2007, 09:02 AM
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[QUOTE]Originally posted by rs6er
[B] Quote:
You'll get a nasty shock unless you have thick rubber gloves and thick rubber boots and don't lean on the car/engine. It sounds to me like the spark is jumping to the case instead of going thru one of the plugs.
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1980 Carrerarized SC with SS 3.2, LSD & Extras. SOLD! 1995 seafoam-green 993 C2, LSD, Sport seats. Abstract Darwin Ipso Facto: "Life is evolutionary random and has no meaning as evidenced by 7 Billion paranoid talking monkeys with super-inflated egos and matching vanity worshipping illusionary Gods and Saviors ". 
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04-23-2007, 09:25 AM
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1981 Porsche 911SC
1985.5 Porsche 944 2.5L Supercharged 
911 SC
Panamera
ME 262 (SOLD)
Colibri
Gas Mizer
Mileage King
Dog Bus
