Engine Making "throaty" Sound After Changing Plugs

IronWorker · October 18, 2005

Changed the plugs and it runs/fires well except when accelerating hard - it makes a deep throaty sound that it did not do before. Seems to not accelerate quite as well as before also.

The only thing I did differently this time was coat the threads with anti-seizing material (careful not to get any on prongs where the plug fires) and I tightened them a bit more, because when I was removing the old ones, they where just a bit loose and not as snug as when I put them in a couple years ago. The plugs say 19 ft. lbs to tighten, so I probably have gone over this. :unsure:

Should I loosen them up a bit? or do something else?

dcfish · October 18, 2005

Changed the plugs and it runs/fires well except when accelerating hard - it makes a deep throaty sound that it did not do before. Seems to not accelerate quite as well as before also.
The only thing I did differently this time was coat the threads with anti-seizing material (careful not to get any on prongs where the plug fires) and I tightened them a bit more, because when I was removing the old ones, they where just a bit loose and not as snug as when I put them in a couple years ago. The plugs say 19 ft. lbs to tighten, so I probably have gone over this.

Should I loosen them up a bit? or do something else?

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Were they gapped properly? Although they are supposed to come gapped from the factory it is a good idea to make sure they are properly gapped before install.

IronWorker · October 18, 2005

Were they gapped properly? Although they are supposed to come gapped from the factory it is a good idea to make sure they are properly gapped before install.

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Yes, I checked the gaps and made a minor adjustment on a couple - shouldn't be an issue.

Toysrme · October 18, 2005

Pull them back out.

The gaps come pre-set on any spark plug you're actually suppose to use.

.043

Also the torque rating for the plugs in the aluminum head are 13lb-ft, not 19+.

And lastly, if it's not an NGK, or Denso plug, you need to ditch it anyway.

AFA the funny sound from the engine, it's either from poor combustion, a combustion chamber leak, or maybe a vacuum leak.

mburnickas · October 18, 2005

Changed the plugs and it runs/fires well except when accelerating hard - it makes a deep throaty sound that it did not do before. Seems to not accelerate quite as well as before also.
The only thing I did differently this time was coat the threads with anti-seizing material (careful not to get any on prongs where the plug fires) and I tightened them a bit more, because when I was removing the old ones, they where just a bit loose and not as snug as when I put them in a couple years ago. The plugs say 19 ft. lbs to tighten, so I probably have gone over this.

Should I loosen them up a bit? or do something else?

←

How do you know you torqued them too much? Did you use a torque wrench? I hope you are using an inch'lb wrnech here. I never use a torque wrnech on plugs since I have been messing with them. To easy to strip them.

Also as soon as you lube threads you are adding torque values to the limits. Each lube is different.

As Toysrme stated you are threading into an ALu block and can strip threads easy. Also the OEM gap is .044. My Denso's came pre-gapped soit was just install them.

Lastly, as Toysrme stated if it is making a noise, you more then likely removed a vac line without knowing it.

justin97 · October 18, 2005

Changed the plugs and it runs/fires well except when accelerating hard - it makes a deep throaty sound that it did not do before. Seems to not accelerate quite as well as before also.
The only thing I did differently this time was coat the threads with anti-seizing material (careful not to get any on prongs where the plug fires) and I tightened them a bit more, because when I was removing the old ones, they where just a bit loose and not as snug as when I put them in a couple years ago. The plugs say 19 ft. lbs to tighten, so I probably have gone over this.

Should I loosen them up a bit? or do something else?

←

How do you know you torqued them too much? Did you use a torque wrench? I hope you are using an inch'lb wrnech here. I never use a torque wrnech on plugs since I have been messing with them. To easy to strip them.

Also as soon as you lube threads you are adding torque values to the limits. Each lube is different.

As Toysrme stated you are threading into an ALu block and can strip threads easy. Also the OEM gap is .044. My Denso's came pre-gapped soit was just install them.

Lastly, as Toysrme stated if it is making a noise, you more then likely removed a vac line without knowing it.

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is your air box tight?

tckcumming · October 22, 2005

Changed the plugs and it runs/fires well except when accelerating hard - it makes a deep throaty sound that it did not do before. Seems to not accelerate quite as well as before also.
The only thing I did differently this time was coat the threads with anti-seizing material (careful not to get any on prongs where the plug fires) and I tightened them a bit more, because when I was removing the old ones, they where just a bit loose and not as snug as when I put them in a couple years ago. The plugs say 19 ft. lbs to tighten, so I probably have gone over this.

Should I loosen them up a bit? or do something else?

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My '93 ES300 sounded just the same as you describe a few years ago. Only made the sound on hard acceleration. Took a long time to track down the culprit...

The flex joint in my exhaust y-pipe had separated. Looked perfectly fine when checked with the car on the rack. When on the road accelerating, however, the engine would rock slightly on its mounts, the broken flex joint would open up a bit - rumbly throaty sound would escape. Replaced the y-pipe... sound disappeared.

Worth a look. perhaps. If you're going to check this, the best way is to put the car up on a rack with someone sitting in it. Start the engine, foot on brake (VERY important!!) put the car in gear and rev the engine a bit. Second person under the car can look/feel for exhaust leaking from pipe. If you don't put the engine under load like this while you check it, the pipe won't open up if it's separated and all will look well... even though it's not.

BTW, if your "dogbone" is worn/broken, the flex joints in the exhaust can be put under extra strain, causing eventual grief.

tck...

IronWorker · October 31, 2005

Update:

Thanks for all of the input from everyone.

I tried the simplest thing first - Got some Denso Iridium plugs (pre-gapped) and put them in, without using the anti-seize compound, and not too tight this time.

Took it out for a test drive and the deep sound is gone when accelerating hard. It seems to have the normal good level of power as before.

Thanks again. :)

dcfish · October 31, 2005

Update:
Thanks for all of the input from everyone.

I tried the simplest thing first - Got some Denso Iridium plugs (pre-gapped) and put them in, without using the anti-seize compound, and not too tight this time.

Took it out for a test drive and the deep sound is gone when accelerating hard. It seems to have the normal good level of power as before.

Thanks again. :)

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:cheers: