2 blown spark plugs...how much HP was I losing?

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BetterBaGT

New Member

Jun 8, 2010

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Phoenix, AZ (unfortunately)

Jun 28, 2010

#1

• Jun 28, 2010

• #1

Long story short, I had an air leak in the intake manifold gasket so I decided to replace it along with the spark plugs (while it was all opened up). When removed, only 6 of the 8 were functioning. So, how much HP was I losing from only have 6 fire? My mechanic said around 100 HP but that seems unrealistic to me.

 

bhuff30

Founding Member

Dec 11, 2001

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Olathe KS

Jun 28, 2010

#2

• Jun 28, 2010

• #2

If only 6 were working all the time, then the engine would be very rough and you would know there was something very wrong. Just go out an unplug 2 wires and see how it runs!

I'm guessing 2 of the plugs were just occasionally not working, causing an occasional misfire, resulting in little power loss. I guess if you want to assume 2 plugs weren't firing at all, then you could multiply 2/8 by your power... 2 / 8 * 260 = 65hp

 

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BetterBaGT

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Jun 8, 2010

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Phoenix, AZ (unfortunately)

Jun 28, 2010

#3

• Jun 28, 2010

• #3

bhuff30 said:

If only 6 were working all the time, then the engine would be very rough and you would know there was something very wrong. Just go out an unplug 2 wires and see how it runs!

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Well there didn't appear to be any major problems when driving it. I've driving other GT's and it felt the same to me. I did get a chance to look at the old spark plugs and all of them (especially the 2) seemed pretty bad. All I know is the mechanic said that 2 were in such bad shape that he thought they hadn't been firing. We will see tomorrow when everything gets put back together and I take it on the road.

 

Maxpowers

Member

Sep 9, 2009

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Pittsburgh, Pa

Jun 29, 2010

#4

• Jun 29, 2010

• #4

It is very obvious it you are missing a cylinder all together, and even more obvious if you are having spark issues because your motor will hesitate under heavy acceleration.

 

N8Dogg98

15 Year Member

Apr 4, 2005

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MN

Jun 29, 2010

#5

• Jun 29, 2010

• #5

Drive a 96-98 NPI stang and compare it to your car. If they feel the same, you're probably running on 6 cylinders.

 

Notchbck93

New Member

Dec 9, 2003

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IL

Jun 29, 2010

#6

• Jun 29, 2010

• #6

BetterBaGT said:

Long story short, I had an air leak in the intake manifold gasket so I decided to replace it along with the spark plugs (while it was all opened up). When removed, only 6 of the 8 were functioning. So, how much HP was I losing from only have 6 fire? My mechanic said around 100 HP but that seems unrealistic to me.

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You had no check engine light on?


Trust me if you had two fouled plugs or bad coils, you'd not only feel it, your car would be beaming with the CEL.