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Registered
Join Date: Jun 2023
Posts: 11
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Loud pinging on idle in 71 911E
Hi, Ive seen this issue mentioned on the forums but not really any definitive answer (that Ive read)
I have a 71 911E 2.2ltr and on idle it has a loud, random, pinging sound coming from the engine. Honestly it sounds like a spanner is rattling around in the airbox - (its not.) And not a backfire. Also it idles well and otherwise smooth. Ive had the MFI rebuilt, and it has new plugs, leads, CDI and frankly runs great. It has heaps of power that it didnt before all the work was done. And it used to run really rich - the reason I had the MFI done, we couldn't adjust the mixture screw, and the plugs were black. So yesterday I took the airbox off put my synchrometer on each venturi and when it pings the suction drops off almost completely ONLY on number 3 cylinder. My guess is I have a sticking exhaust valve or that valve spring is broken, sticking or weak and not returning the valve to closed - thus allowing the fuel intake suction from the piston to also draw air back through the open exhaust valve (reducing suction) until it slams shut again on compression and makes that loud ping. Is that even possible? Ive put some Liqui Moly cleaner in the fuel to see if that cleans the cylinder and valve stem in case its just got some residual carbon build up in there and sticking. And while it does does seem to be less frequent it still occurs and frankly Im not happy there's any unknown noise coming from the engine. Anyone had this and found the answer? Thanks in advance. Craig |
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10-01-2023, 04:53 PM
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PCA Member since 1988
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Happened to me on an engine that sat in the car without running for 20 years. The old fuel varnished the intake and/or exhaust valves, and a few of them were sticking. I was able to free them up by squirting carb cleaner directly on the valve stems and cranking the engine through a bunch of times, then squirting WD40 on them. Seemed to work out.
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1973.5 911T with RoW 1980 SC CIS stroked to 3.2, 10:1 Mahle Sport p/c's, TBC exhaust ports, M1 cams, SSI's. RSR bushings & adj spring plates, Koni Sports, 21/26mm T-bars, stock swaybars, 16x7 Fuchs w Michelin Pilot Sport A/S 3+, 205/55-16 at all 4 corners. Cars are for driving. If you want art, get something you can hang on the wall! |
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10-01-2023, 07:13 PM
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It's a 914 ...
Join Date: Jan 2008
Location: Ossining, NY
Posts: 4,685
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If you pop off your valve covers, a broken spring will be evident if there is one. Maybe it's just what PeteKz mentioned. If you're hearing possible metal to metal contact, personally I wouldn't start the engine again until I better understand what's happening. Hopefully no bent valves yet.
Last edited by stownsen914; 10-02-2023 at 06:27 AM.. |
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10-02-2023, 06:06 AM
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