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'82 NA Engine Pinging on initial sharp throttle

 
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XLR8  



Joined: 30 Mar 2016
Posts: 112
Location: Byron Bay, Australia

PostPosted: Thu Jun 07, 2018 5:33 pm    Post subject: '82 NA Engine Pinging on initial sharp throttle Reply with quote

Hi all, as per the title, I am experiencing pinging on initial sharp throttle "blip" (maybe 1/2 - 1 sec) and then she's all fine. Seems okay under load.

Any ideas?

Do I need to richen the mix a little?

Fouled injector causing a lean cylinder?

I don't think there are any vacuum leaks. I am running premium fuel and timing is set around 8deg BTDC.

Thanks in advance ....
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'81 Porsche 924 NA
'89 Eunos Roadster NA6
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Ian89C4  



Joined: 01 Apr 2011
Posts: 525
Location: North Carolina

PostPosted: Sun Jun 24, 2018 12:57 am    Post subject: Reply with quote

Could also be that the sudden increase in RPMs has a "slapping" effect of the cam followers - flat tappet after all. That may cause a pinging sound. If I remember correctly, if you are running lean or there is too much advance on the dizzy, you would hear it worse at higher RPMs.

You can try richening her up a little and see what it does, just make sure you can get her back into Stoich range with the tools you have - if not, it may cause problems later on down the road.

If that doesn't do anything, I may do a quick valve lashing check per the manual. May be a bit too much space in there.

Good luck.

Cheers
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Ian Edgerly
Spiveys Corner, North Carolina

Current:
1981 924 Weissach Race Car ("Serenity")
1980ish 931 ("Alice")
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Fasteddie313  



Joined: 29 Sep 2013
Posts: 1549
Location: Not Detriot - NMI

PostPosted: Sun Jun 24, 2018 1:48 am    Post subject: Reply with quote

Mine does this if my distributor is a little too advanced..
Are you sure your timing is set to spec and your distributor vac lines are correct?
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1980 931S - LSD - FMIC - GTS fuel - hobby
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XLR8  



Joined: 30 Mar 2016
Posts: 112
Location: Byron Bay, Australia

PostPosted: Mon Jun 25, 2018 9:35 am    Post subject: Reply with quote

Thanks Fasteddie313 and Ian89C4,

Timing is set conservatively, and I think all the Vac lines are good (but checking them is ongoing).

I have tried richening her up, but it does not seem to alleviate the issue.

Cam followers were adjusted about 1000mi ago, so I think they are good.

I am leaning more and more to a clogged fuel injector leaning out the mix in one cylinder, at the initial throttle application. The pinging noise is there, but it isn't alarming, so I suspect it's just one cylinder....
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'81 Porsche 924 NA
'89 Eunos Roadster NA6
'06 Landcruiser HDJ100
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Ian89C4  



Joined: 01 Apr 2011
Posts: 525
Location: North Carolina

PostPosted: Mon Jun 25, 2018 10:37 am    Post subject: Reply with quote

Pull all four injectors out, put em in glass jars, jump the fuel pump relay, turn the ignition to run, push up on the air plenum and see what they do.

Look forward to hearing results.

Good luck!
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Ian Edgerly
Spiveys Corner, North Carolina

Current:
1981 924 Weissach Race Car ("Serenity")
1980ish 931 ("Alice")
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