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Old 09-16-2012, 05:41 PM
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85 impala timing

hey guys, i have a 85 impala with a 305, quadrajet, and its all computer controlled with esc

well i noticed my timing is off because i hear slight pops through the exhaust and it goes away when i jump pins A and B to stop the computer advance.

i bought an aftermarket timing pointer, found TDC and marked it on the new pointer. On the timing tape it shows 0* when the A and B terminals are jumped. and shows 20* when running normally at idle.

my questions are

1) is it normal for the computer to be advancing that much at idle?

2) where do i go from here?


Im very new at this, just bought the car this year so please bear with me
Let me kno if you guys need more info

thanks,
clint

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Old 09-16-2012, 07:06 PM
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20 is pretty normal .
Not to sure timing would be the issue here. Did the symptom occur after a timing adjustment? Did anyone adjust the timing?
Sounds like air getting into the exhaust stream. Maybe the EGR valve is sticking?
Could be also the carb is too rich. Also faulty AIR check valves can let air into the exhaust when not wanted and cause a pop or a burble.
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Old 09-16-2012, 07:58 PM
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20 is pretty normal .
Not to sure timing would be the issue here. Did the symptom occur after a timing adjustment? Did anyone adjust the timing?
Sounds like air getting into the exhaust stream. Maybe the EGR valve is sticking?
Could be also the carb is too rich. Also faulty AIR check valves can let air into the exhaust when not wanted and cause a pop or a burble.
Well when I bought the car my buddy set the timing because it was running really rough. I didn't have a timing light so it was set by ear, and he put a chrome cover on of course.
I just noticed it now a few months after the timing was set, it sounds like a quiet pop or thump. No repetition or anything. I could only hear it when I'm by the exhaust and it kinda shakes the car. And I see a spike in the a/f when it happens, maby 16.0 max

I'm not sure what the AIR check valves are but I'll research it.

Theres a tube from my cat that comes up on the pass. side and it sucks, I'm not sure what that is.

We also replaced the huge stock air cleaner with a chrome one and removed the AIR tubes from the manifold

I have an a/f ratio gauge that's reading 14-15 so its not too rich

I'll check the egr valve, I didn't think of that.

Thanks for the reply
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Old 09-17-2012, 12:46 PM
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Here is a video that will probably describe the noise better than words,
It was taken on a cell phone so its crappy quality.

https://www.youtube.com/watch?v=KPeL...e_gdata_player">https://www.youtube.com/watch?v=KPeL...e_gdata_player" type="application/x-shockwave-flash" width="425" height="350">

I'll check the EGR valve and if I could find the AIR check valves I'll check that too later on today.

Thanks for the help
Any comments or ideas are greatly appreciated
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Old 09-17-2012, 12:52 PM
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Fail

Exhaust popping - YouTube
"> Exhaust popping - YouTube
" type="application/x-shockwave-flash" width="425" height="350">
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Old 09-17-2012, 05:18 PM
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Sounds typical for a car with no exhaust system, however the tube on the passenger side that you said " sucks" needs to be plugged. It is allowing air to be pulsed into the exhaust stream...most likely causing the issue.
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Old 09-17-2012, 06:00 PM
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Sounds typical for a car with no exhaust system, however the tube on the passenger side that you said " sucks" needs to be plugged. It is allowing air to be pulsed into the exhaust stream...most likely causing the issue.
Cool I'll do that, thanks for the help
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Old 09-17-2012, 07:32 PM
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That definitely worked, if I could hit the "thanks" button twice I would
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Old 09-17-2012, 07:43 PM
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Excellent, glad to help
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Old 10-14-2012, 08:05 AM
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You can't set timing by ear.... these CCC and all GM EFI systems are usually set to 0 advance with Bypass wire disconnected, usually a tan wire with plug from the EST-ICM modle in distributor. ESC is module for knock system retard, Disconnect this wire and set timing to 0 with light. Then when plugged back in ECM will control timing and can be 10 to 20 degrees advanced. Will also set a DTC so disconnect battery to clear codes.
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Old 10-14-2012, 12:25 PM
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Quote:
Originally Posted by EagleMark View Post
You can't set timing by ear.... these CCC and all GM EFI systems are usually set to 0 advance with Bypass wire disconnected, usually a tan wire with plug from the EST-ICM modle in distributor. ESC is module for knock system retard, Disconnect this wire and set timing to 0 with light. Then when plugged back in ECM will control timing and can be 10 to 20 degrees advanced. Will also set a DTC so disconnect battery to clear codes.
Cool, that clears things up a bit.
Thanks
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Old 11-18-2012, 10:25 AM
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yea you have to disconnect the by pass wire, One the b bodies its over near the passenger hood hinge area, and I hope the timing pointer was in the same place as the old cover, I know alot of those 80's SBC's had the pointer under the W/P at 12o'colck, using a aftermarket on with the side and not swapping the harmonic balancer with have the timing marks WAY OFF.
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Old 11-18-2012, 01:16 PM
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Quote:
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yea you have to disconnect the by pass wire, One the b bodies its over near the passenger hood hinge area, and I hope the timing pointer was in the same place as the old cover, I know alot of those 80's SBC's had the pointer under the W/P at 12o'colck, using a aftermarket on with the side and not swapping the harmonic balancer with have the timing marks WAY OFF.
Yea my factory timing pointer was around 12 o'clock right behind the water pump, but since my buddy got me a chrome timing cover without a pointer I had to buy a new 2 o'clock pointer which really screwed things up, so I found TDC again and made a new slit on the balancer inline with the new pointer
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