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post #1 of 29 (permalink) Old 01-23-2016, 10:51 PM Thread Starter
 
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389 running rough

Hey guys. My 389 has been on the fritz. Maybe u guys have an insight or similar experience. Sorry in advance for long write up but..
Here's my set up;
65 bonneville factory rebuilt 389 with edelbrock 650 carb. Installed pertronix 3 about 4 yrs ago. 400 trans. Last time I timed it was set around 12 and ran perfectly. Car has ran great and started great for the past 5 years with no issues.
So, I only get the car out on the weekends or every other weekend. Took if for a drive a month ago, all normal, exit freeway and Come to stoplight. Car starts to have a rough idle and is going from idling good to rough bogging idle. I lightly brake stand it to feed it a little fuel and bogging stops and runs fine. Kinda still Boggs at idle before I get home. Just kept on the gas to keep Rpms up.
A week later, same story.
Last week: start car, cruse down to get coffee down the street and runs fine. Go to leave, start car and bogging rough idle starts. I start driving away and motor starts pinging the whole way home. Along with rough running and barely staying running. Never stalled though.
Plugs look good, light brownish. Normal color. Car wasn't and hasn't been running rich. Inside cap and rotor very very clean. Figured it may have been the vacuum advance. Looked original. Replaced it and vacuum advance was bad after the suck test. Started car and still had rough idle.
When I checked the timing i noticed on the timing light, that when the car would hesitate or kinda "miss" the light flashing wouldn't be consistent flashing. It fluctuated with the miss. Which leads me to think its the pertronix module because when the car suddenly idles good, the flashing is consistent like it should be. But then idles rough again. I put the car in gear and it would run worse or stall. But isn't hard to start.
Now there's no manifold vacuum port on this intake. Vacuum advance line came from (as long as I've had the car) the carb port on passenger side. Since it ran bad after changing the va, I read that the proper side for VA is the driver side port. Switched them and tried adjusting timing and no difference in idle roughness.
For kicks I put a new fuel pump in because I noticed fuel was very little in filter and figured maybe it was starved too. No change.
I apologize for the long write up but trying to eliminate possibilities and narrow it down.
Could bad vacuum advance cause the rough idle at first and mess up the pertronix? I'm at the basic frustrated point of a lost weekend day/money spent/no progress point, so any info would help.
Thanks guys!
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post #2 of 29 (permalink) Old 01-24-2016, 09:41 AM
 
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Johnny, you have done some investigating already,....of course rough idle can be many things and petronix can't be ruled out, yet...

a miss will cause your timing light to do that as well..

but it sounds like you might have a cylinder missing, rough idle, worse under load. this can be caused by electrical or fuel air....

first electrical, by looking for a plug or plug wire missing by shorting to ground, use a misfire pen, a spark tester or watch it in dark, ....to see if stray spark is apparent. Bad plugs, bad plug wire can cause a miss.

fuel air on a carburated car can be affected by a vacumn leak near an intake runner...that causes one cylinder to miss because too much air....sometimes does not happen until car heats up, and leak gets worse from say expansion of metal. check around intake manifold gasket for vac leak listen, feel...

at the back they get worse a temp fix is a dab or RTV sealant over the leak, let it set up....then retry...if so replace the gasket

try a different petronix or points if that does not work...

Pinging by the way can be too much timing, if you dial it back 2 to 4 degrees it may eliminate that. Also you need to know if that vac can is pulling full manifol vac...which means at idle...or just ported vac...which is only when throttle is opened...can't tell by looking...just pull the hose off at carb and see ifit is pulling vac at idle or not.....so you know, because it effects timing depending on the vac can.

also make sure distributor springs and weights are moving freely and not stuck advanced, causing a miss and pinging....

also make sure your distributor is down tight....

if nothing helps there make sure your choke is or fast idle screw is not sticking and causing an overly rich condition once fully warmed up''''

like it runs good initially ...then gets rough

PCV systems cause rough idles too make sure it is not clogged and all hoses are good...just keep investigating!

You will get it....pulling for Ya!
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post #3 of 29 (permalink) Old 01-24-2016, 10:14 AM Thread Starter
 
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Thanks la mans guy. I'm making a list of stuff to eliminate. Thank u for all the info. I'm going to start with putting points back in and then investigate vacuum.
Thanks again!
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post #4 of 29 (permalink) Old 01-24-2016, 10:53 AM
 
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Johnny one thing I like to do is find out is it an individual cylinder miss....

or related to a whole engine operation that effects all cylinders?

Points check is a good start...and since you have been around the plug wires and dizzy make sure your plug wire routing and firing sequence are correct...also your wires to the coil are tight.

one way to find a cylinder miss is to use an insulated pliers, not metal don't get shocked,....and pull a plug wire while running if the engine runs rougher that cylinder was firing...if no change than you have a miss there...

I like the misfire pens and spark testers just easier....but this could be a plug gapped too much or not enough..

when I put in a crane module like a petronix I had to open the plug gap to .45....as the factory 35 i think it was was good with points but not the petronix...did not run as good...so a simple plug gap can cause a misfire, and under load....

let us know and lots of guys on here with great knowledge...(not Me)

they will chime in and help.....
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post #5 of 29 (permalink) Old 01-24-2016, 11:56 AM
 
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Garage
As simple as this sounds, the gas itself could be adding to your problem if you are using the ethanol laced gas. You really are not driving it much and while it sits, the ethanol picks up water and over time, you could build up a little. I use the Stabil 360 additive you can pick up a Walmart. It can help your engine run smoother and break down the water.

Do the usual checks as already mentioned as this is sometimes the only way to narrow it down by knowing what it isn't. I am leaning towards an electrical issue. Did you replace the factory resistor ignition wire to the coil with a 12-volt sourced wire?
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post #6 of 29 (permalink) Old 01-24-2016, 07:53 PM Thread Starter
 
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Lamans- good point about the plug gap. Think mine were at .35 when I put them in. But never had a problem. It was hard to keep track of the miss because it would happen then run fine. But Thanks again la mans guy.
Jim- good suggestion on the stabl. I'll look into that. And I don't know about that wire because I got the car with an igniter 2 already in it. Since I just bought the car I swapped out for the new pertronix 3. That was about 5 years ago. And never had a problem with the motor til last week.
I have since removed the pertronix and sending them into the company to test out. I have parts to put points, condenser, ballast etc back in but realized I have no mounting screws. The new ones didn't come with it and the pertronix ones are not usable for points. So I'm at a stand still for now. Until I hear back from pertronix.
I'll keep u guys updates asap. And thank u for all the great advice
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post #7 of 29 (permalink) Old 01-25-2016, 08:22 PM Thread Starter
 
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Got a little update.
I said before the car came with an ignitor 2 set up. And I put an ignitor 3 in it shortly after I purchased it. Well, I would only assume it was done right because the car ran great. And after installing the ignitor 3 I've had no troubles for years. Well I guess the wire to the coil is the original resistance wire which is not a full 12v while running. And the tech at pertronix said my symptoms were due to not enough Volts to coil. After testing volts it was very low. My battery isn't 100% but enough to start the car. But that's what I'm going for right now. I mailed in the module and coil to pertronix to be tested anyway. And will either have to install their power relay or rewire for a solid 12v to coil while running.
After all this I'll let ya know if that's what ails me
Thanks again guys!!
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post #8 of 29 (permalink) Old 01-25-2016, 09:12 PM
 
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You will get it. Johnny, ..but if it ran great for 3 years, on the coil wire that you had installed....why would that now be the culprit?

If module was not running because it needed more volts as Petronius says, than either it malfunctioned internally, as you suspected or...your alternator or wiring is not delivering adequate voltage....like a loose belt or bad alternator.

Don't know what about Petronius but my crane module leaves in place the original ballast resistor wire as designed, same as the points. I discussed that with Crane Tech, and it works fine, but Petronix may be different.

Anyway, you are on it and I agree with Pontiac Jim that it was a good place to examine that resistor wire since the module is not the points....

Let us know what you find....
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post #9 of 29 (permalink) Old 01-26-2016, 08:24 AM Thread Starter
 
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I wondered the same thing about why would it be acting up now, the guy said that it can run but eventually the module will start having little issues. And since I really don't drive the car long distances and only once, maybe twice a month he said it wouldn't act up right away. Either way I'm having it tested and will put it all back together with the proper 12v wire to the coil, and Hope that's it
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post #10 of 29 (permalink) Old 01-26-2016, 11:14 AM Thread Starter
 
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Do you guys know if I can run a jumper on the ign switch from the START post to the RUN post? I read that you can in order to give the coil 12v while running. Then add a non resistance wire from the RUN post to the coil. Apparently people say it can be done but should it be done? Will a constant 12v thru the RUN post eventually burn out the switch?
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