 spark plug gap closed on two plugs, what causes this? |
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| siverson |
 Jun 13 2016, 09:23 PM
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#1
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Advanced Member  Group: Benefactors Posts: 2,451 Joined: 5-May 03 From: San Diego, CA Member No.: 654 Region Association: Southern California 
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hi - quick question from the garage. cdi box died on my six. got replacement and car starts right up (good). but runs like crapola right away. pulled the plugs and on two the electrode (term?) is no touching the plug.
is this why my cdi boxed died? or is this a result of it dying? or? plugs were 1k miles old. cdi box was 46 years old. |
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| siverson |
Jun 14 2016, 12:16 PM
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#2
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Advanced Member Group: Benefactors Posts: 2,451 Joined: 5-May 03 From: San Diego, CA Member No.: 654 Region Association: Southern California
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Interesting, thanks for the feedback.
I don't think the plug length is the issue. The plugs were installed by the shop that built the engine and they use them all the time. I also had several other new plugs in the garage are various brands for Porsche six cylinder engines, and they were all the same length. So, just to test, I installed a new set of FR5DTC plugs. They aren't the best for this 2.0 engine (they are correct for the 964 3.6) but everything runs and sounds fine. Vrooom. I've ordered a set of WR5DC (what CDI box mfgr/PartsKlassik recommends) that I'll replace these with. The tach seems more bouncy than normal with the CDI box, but I'll take a look at the points (or maybe replace with Pertronix). I'll have to hook up my Air/Fuel ratio meter to see whats up. A boroscope would be nice, but I don't have one... Hmmm... A piston hitting a spark plug on high rev doesn't really make sense to me either, but I also have WAY less experience with this stuff than brant. -Steve |
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| brant |
Jun 14 2016, 12:24 PM
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#3
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914 Wizard Group: Members Posts: 11,824 Joined: 30-December 02 From: Colorado Member No.: 47 Region Association: Rocky Mountains 
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QUOTE(siverson @ Jun 14 2016, 12:16 PM)  Interesting, thanks for the feedback. I don't think the plug length is the issue. The plugs were installed by the shop that built the engine and they use them all the time. I also had several other new plugs in the garage are various brands for Porsche six cylinder engines, and they were all the same length. So, just to test, I installed a new set of FR5DTC plugs. They aren't the best for this 2.0 engine (they are correct for the 964 3.6) but everything runs and sounds fine. Vrooom. I've ordered a set of WR5DC (what CDI box mfgr/PartsKlassik recommends) that I'll replace these with. The tach seems more bouncy than normal with the CDI box, but I'll take a look at the points (or maybe replace with Pertronix). I'll have to hook up my Air/Fuel ratio meter to see whats up. A boroscope would be nice, but I don't have one... Hmmm... A piston hitting a spark plug on high rev doesn't really make sense to me either, but I also have WAY less experience with this stuff than brant. -Steve I don't know why... I'm hoping jeff or someone chimes in on that but when I had it happen it was a 2.0 motor also and I know the factory changed the plug location and combustion shape on the 2.2 heads.... I wonder if the plug location on the 2.0 head is closer/more susceptible to this? |
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Posts in this topic
siverson spark plug gap closed on two plugs Jun 13 2016, 09:23 PM
siverson 914 Jun 13 2016, 09:24 PM siverson 914 Jun 13 2016, 09:25 PM stugray Cyl touching? (Does it have High CR pistons? does ... Jun 13 2016, 09:40 PM nine9three The only thing I know that would cause this would ... Jun 13 2016, 09:42 PM veekry9 (Pelican Pix)
They can look as bad as this before... Jun 13 2016, 10:34 PM
nine9three
Carbon buildup on the pistons are usually the cu... Jun 14 2016, 10:12 AM brant You missed a shift or most likely over revved it o... Jun 13 2016, 11:07 PM r_towle I'm very unclear on how a mis shift or over re... Jun 14 2016, 09:00 AM brant on a -6 with high compression and high lift cams t... Jun 14 2016, 09:24 AM r_towle
on a -6 with high compression and high lift cams ... Jun 14 2016, 01:08 PM Luke M I would check to make sure those are the proper pl... Jun 14 2016, 09:33 AM Frankvw Mmmmm interesting topic.
but to be honest...I am r... Jun 14 2016, 10:36 AM brant
Mmmmm interesting topic.
but to be honest...I am ... Jun 14 2016, 10:40 AM siverson New plugs.
-Steve Jun 14 2016, 12:18 PM siverson In there now.
-Steve Jun 14 2016, 12:19 PM stugray Engine parts DO flex.
The greatest stress in an en... Jun 14 2016, 01:04 PM |
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