erratic spark

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Feb 18, 2008 | 06:31 PM

JWH2

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erratic spark

I have a 1986 F250 460 motor,I wrote awile back about burning gaskets at the egr plate & carb.I bit the bullet and replaced everthing,new edelbrock man. egr plate,and rebuilt carb. from Pony carb.it ran great until a few days ago,started missing at idle.Checked & replaced gaskets still got a miss ,checked spark at dist.cap to plug wire very inconsistent spark any ideas would be appreciated

Feb 18, 2008 | 07:07 PM

klxstiffler

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first step would be to remove the cap and inspect the bottom side for cross arcing between cylinders. sometimes a small pinhole will form and spark will arc from one cylinder to another. usually you can see lines where it's happened or burn marks around a pinhole. good luck.

ps. check spark from coil to dist also to make sure it's normal from the coil.

Feb 20, 2008 | 08:15 PM

JWH2

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Thanks for the response klxstiffler,I checked the spark from the coil and there's enough to set the motor on fire,changed the cap & rotor still same problem, not much left to it except the mag. pickup & the module

Feb 21, 2008 | 07:17 PM

Holmesuser01

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From: Asheville, NC

I doubt that there is a problem with the pickup. Have you tried swapping a different module? Sometimes the module is the culprit. If it continues to act up, I'd return the original module and keep the other one for a spare. They run around $20 at Autozone.

I am referring to the module with the blue plastic wire grommet.

EDIT:

Plug wires dont last like they used to. I have seen some of them get crappy after just a couple of years of use!

Feb 22, 2008 | 12:34 PM

PerfDistIgnition

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Quote:

Originally Posted by JWH2

You might want to check your plug wires' resistance with an ohm meter. If one has a lot more resistance on a per ft. basis, you may just need to replace one wire.

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Feb 22, 2008 | 01:00 PM

JWH2

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Trust me when it goes from running like a new truck to shaking the coffee cup out of the holder( I really don't have a cup holder but you get my point) at idle somthing happened,I haven't been able to mess it for a few days to much rain and it's to tall to squeeze in the garage. thanks for the responce

Feb 22, 2008 | 01:21 PM

ArdWrknTrk

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From: EXTREME southwest CT

I might think that the distributor shaft is wobbling around.

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Feb 22, 2008 | 06:20 PM

ArdWrknTrk

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From: EXTREME southwest CT

You could try spraying a can of WD40 or carbcleaner around the EGR spacer and the edges of the intake manifold, if it picks up you've found it.
How's the timing?

Feb 22, 2008 | 06:23 PM

#10

uncle.stosh

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You can spray carb cleaner or something like that around while it's running. If there is a leak, the engine will smooth out and speed up briefly.

Feb 22, 2008 | 06:24 PM

#11

uncle.stosh

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Wow, ArdWrknTrk you beat me to it.....

Feb 22, 2008 | 06:26 PM

#12

ArdWrknTrk

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From: EXTREME southwest CT

Luck 'O the draw.
I'd still like to see if his timing is jumping around, as in clapped out chain.

Feb 22, 2008 | 06:30 PM

#13

JWH2

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thanks guys, the usual culprit is the egr plate to carb,but I changed those gaskets

Feb 22, 2008 | 06:35 PM

#14

JWH2

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I forgot to mention the motor only has about 30,000 miles on it ,and the timming seems
to be staying at 8%

Feb 22, 2008 | 06:40 PM

#15

ArdWrknTrk

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30K? it's not even broken in.

If you rev it up while looking w/ the timing light does the mark advance and retard smoothly?
Yea, I know there's no human way to do this by yourself.