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Registered
Join Date: Sep 2004
Location: Southern California
Posts: 85
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cis issues/clicking relays
Hello all,
I posted about a week ago about my rough idle issues ('81 911SC). I replaced the fuel pump relay, fuel pump fuse, and the interior light fuse. The car fired up fine but now have a very slight rough idle and clicking O2 sensor relay only at idle. The relay does not click under acceleration. I replacd the O2 sensor relay and the car fired up fine and warmed up w/ no idle issues. Went for a spin and I noticed that the O2 relay and the fuel pump relay are clicking only at idle and not while I'm accelerating. Now after that quick spin I notice a rough idle and clicking relays. Also the new thing that I noticed is when I turned on the headlights, I noticed that the engine seemed to bogg and the rough idle became worse. I stepped on the accelarator and the issues were gone (relay clicks and rough idle). Any suggestions? I am planning on checking the battery connections. But I thought I'd ask for any other things to check for as well. I read some other posts about the rev-limiter relay and proper grounding straps, and possibly a faulty CDI. Thanks for any help and suggestions. ![]() |
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Registered
Join Date: Sep 2004
Location: Southern California
Posts: 85
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bump
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Registered
Join Date: Sep 2004
Location: Southern California
Posts: 85
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bump again
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Registered
Join Date: May 2001
Location: Peoples Republic of Long Beach, NY
Posts: 21,140
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what are the voltage measurements at the battery at idle and at higher rpm with the lights and heater blower on ?
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Ronin LB '77 911s 2.7 PMO E 8.5 SSI Monty MSD JPI w x6 |
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Location: Southern California
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Unfortunately I haven't gotten that far as to checking. These observations were from last night. Any ideas you might have without the voltage values? Thanks.
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Registered
Join Date: May 2001
Location: Peoples Republic of Long Beach, NY
Posts: 21,140
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well.. I was just suspecting a voltage issue. The first place to start would be the battery. If ok then I would tap into the relay hot trigger wire and see what's happening. Then the relay ground.
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Ronin LB '77 911s 2.7 PMO E 8.5 SSI Monty MSD JPI w x6 |
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Registered
Join Date: Sep 2004
Location: Southern California
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Ok RoninLB bear w/me because I'm new to this. Where is the relay hot trigger located and where is the relay ground. Thanks.
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Registered
Join Date: May 2001
Location: Peoples Republic of Long Beach, NY
Posts: 21,140
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Quote:
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Ronin LB '77 911s 2.7 PMO E 8.5 SSI Monty MSD JPI w x6 |
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Bumping this thread because i have the exact same issue.
Was this ever resolved? From my searches it doesn't seem like many others have this problem. Cortney |
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Join Date: Jul 2013
Location: South East England
Posts: 1,692
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The fuel pump relay ‘chattering’ at idle can be caused by the air metering plate not being adjusted properly or the air box is cracked.
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Johnny thanks for the reply. Following up here for posterity - I ended up re-setting my ignition timing advance and that took care of it. Not sure why improper ignition advance would cause relays to click on & off but resetting it solved the problem for me.
I also likely have air/vacuum leaks somewhere, but I’m planning to do a CIS teardown and rebuild next weekend so we’ll see. |
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