ping at part throttle with intermittant miss at idle - Hot Rod Forum : Hotrodders Bulletin Board
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Old 03-24-2012, 02:12 PM
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ping at part throttle with intermittant miss at idle

ok I had this issue since last year before putting the car away for winter.
I changed coil, installed new distributor (I think i blew the module when i started car with battery buddy hooked up by mistake).
but old one was fine.
took out and hooked up vacum gauge.
needle fluctuates between 17" and 19".
normal is a steady 18".
I readjusted the idle mixture but still has same fluctuations and part throttle ping.
only thing left in the ignition system is the MSD 6AL box and the moroso ultra wires.
btw all cylinders are firing (checked with water spray and temp gun)
pulling the spark plugs and all were black and sooty.

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Last edited by dawg; 03-24-2012 at 02:22 PM.
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Old 03-25-2012, 05:59 AM
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aww cmon guys,
86 views and not a single idea???
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Old 03-25-2012, 06:22 AM
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Hey fellow Navy vet. . Ran poorly and would idle rough. The combo of wide gap and MSD is pretty hard on wires. Worth a look.
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Old 03-25-2012, 07:13 AM
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My Pontiac 455 ran much better when I removed the MSD6AL from the stock single points distributor and put the resister wire back on the coil..

I'd put the ignition back to stock and adjust the vacuum advance...
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Old 03-25-2012, 02:54 PM
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thats my next move
I did change the fuel and didnt notice a difference.
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Old 03-30-2012, 05:22 AM
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ok took MSD 6AL out and running on coil only.
installed known good coil.
regapped plugs
changed fuel (fresh 93 octane in the tank now).
changed fuel filter
installed vacum gauge and it reads between 17"and 19".
still hear the miss or skip at idle.
still pings under load and plugs are sooty black?
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Old 04-24-2012, 07:19 AM
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removed intake and found gasket between 1&3 inlet ports to be leaking between the two and suckin a bit of oil.
replaced intake gasket and insstalled new intake (hey the old one was already off lol)
here is a couple pics.
I hope that was the issue all along?
intake is a polished super victor intake
I had to order a throttle rod conversion to work with the bigger intake.
no more throttle rod anymore!

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Old 04-29-2012, 05:47 AM
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well got the motor reassemled and still had the pinging issue but the miss at idle and sooty plugs are no longer a problem. decided to do a compression test instead of leakdown test and 3&5 were rearing 50 psi!
removed heads and its the head gasket!
check out the head gasket between 3 and 5


there is a bit of a crater im hoping the machine shop can fix it!

Last edited by dawg; 04-29-2012 at 05:53 AM.
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Old 04-29-2012, 07:57 AM
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Quote:
Originally Posted by dawg
well got the motor reassemled and still had the pinging issue but the miss at idle and sooty plugs are no longer a problem. decided to do a compression test instead of leakdown test and 3&5 were rearing 50 psi!
removed heads and its the head gasket!
check out the head gasket between 3 and 5


there is a bit of a crater im hoping the machine shop can fix it!
Probably caused by the pinging. You cant continue to run an engine when it is detonating. Something will eventually blow. Looks like you were lucky and it was just a gasket. Usually it is something more expensive like a piston
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Old 04-29-2012, 03:18 PM
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Wow that looks cruel, you got any vac advance???

Duke
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Old 04-29-2012, 04:03 PM
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mechanical advance no vacum advance.
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Old 04-29-2012, 05:27 PM
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Looks like U will need to puddle weld that head surface to fill the crater, then mill it, tough one there. Looks like burnt oil in the mix too, could have added to the heat and compression in that blow out zone, was the intake gasket leaking maybe?
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Old 04-30-2012, 08:03 AM
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yes intake was suckin oil and that was the initial problem miss at idle and sooty plugs with pinging under load.
fixed intake gasket but it still pinged but sooty plugs and miss were gone.
ran motor for a few mins at a time to troubleshoot then do a compression test etc.
heads are at machine shop and will be fixed for 100.00 a head.
both intake sides will be cleaned up aswell as the milling of the head surface.
a few bucks for the little bit of welding is all.
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Old 04-30-2012, 08:11 AM
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Quote:
Originally Posted by dawg
yes intake was suckin oil and that was the initial problem miss at idle and sooty plugs with pinging under load.
fixed intake gasket but it still pinged but sooty plugs and miss were gone.
ran motor for a few mins at a time to troubleshoot then do a compression test etc.
heads are at machine shop and will be fixed for 100.00 a head.
both intake sides will be cleaned up aswell as the milling of the head surface.
a few bucks for the little bit of welding is all.
Unless there are mechanical problems, pinging under a load is almost always too much ignition timing. It might be too much initial or it is advancing too quickly from the springs being too weak.

If you are using a vacuum advance, it could be supplying too much advance at the vacuum where the ping is occurring. An adjustable vacuum advance will fix that.

The dynamic compression ratio may be too high, the octane too low.

Possible mechanical problems: the timing plate could be sticking or the vacuum advance binding. There could be crossfiring in the distributor cap or through the wires, or the firing order is wrong.
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Old 04-30-2012, 10:22 PM
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Hi, I have problem in my cylindrical piston, itís making noise whenever I changed gear up from 4. I donít know what is causing the problem. Do you think any repair person in new jersey provide home service.
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