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post #1 of (permalink) Old 01-11-2000, 12:45 PM
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ignition problem

I recently installed a pigtail for my distributor on my 87. For some reason it misses under acceleration between 1500 and 3000 RPM, but only from the driver's side. It won't do it if I mash it to the floor, but only when I slowly accelerate. Would I have a bad crimp-on connection that should be soldered or is something inside the distributor fouling up? Sometimes it will accelerate good and I need to hold on the the wheel!

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post #2 of (permalink) Old 01-12-2000, 02:04 AM
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Re: ignition problem

What do you mean "only from the drivers side"? What is the "pigtail"? Are you referring to a wire splice? If so which wire did you splice or tap into?

[img]/wwwthreads_images/icons/cool.gif[/img] MG48 - 88 Bronco
post #3 of (permalink) Old 01-12-2000, 09:30 AM
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Re: ignition problem

I can't believe you have never heard of a "pigtail." The plastic harness that snaps on to the distributor has a habit of becoming brittle and break. I replaced this piece that I purchased from an auto parts store. It has crimp on connections on all 6 wires.
When I say drivers side, I mean the driver's side! My bronco has dual exhaust on it, and it misses out on the driver's side (the side a person usually drives on, with the steering wheel and stuff). It dumps out right below the door, so it is really easy to hear.
I plan to solder the wires when the weather cooperates with my work schedule. If this doesn't fix it, could it be something inside the distributor (ignition module, pick up coil)?

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post #4 of (permalink) Old 01-18-2000, 02:41 PM
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Re: ignition problem

Even though your reply was a little "smart" I will take a shot at diagnosing your Bronco's problem. The ""key" piece of info that I needed clarification on was the "drivers side". If your engine is only missing on one side and it is not fuel injected, which yours is not, then it can only be a couple things. It can't be any of the general ignition items because it is only misses on one side of the engine. It has to be something specific to that side. So we have to look up steam from the rotor and the carb. Either one of the cylinders on that side is not getting gas or spark. A sticking valve is all that could prevent the air/fuel mixture from getting there. A bad plug or wire kills the spark. The spark plug or wire is my guess. If you have changed or cleaned and gapped your plugs recently and all looked good. You need to check the spark plug wires. But don't be fooled. Sometime a plug looks good but does not operate correctly. If you decide to pull them and check go ahead and swap them to the other side to see if the miss follows. Low rpm acceleration causes the highest cylinder pressures your engine gets. This raises the resistance of the spark trying to jump the gap of the plug. If the insulation on your wires is getting old and deteriorated the spark will jump out through it and no spark at the plug results in a miss. It is hard to test the wires unless you have a spark plug lead tester . One way that I have seen people try with mixed success is to spray a water mist on one wire at a time with it laying in place and see if the miss will occur. You might be able to swap some of the wires to the other side if they will reach (I think they will) and see if the problem moves over. There is also the possibility of cross firing. This is where your wires are touching and the insulation is breaking down allowing a spark to jump to a wire whose cylinder press is lower because it is not on the compression stroke thus causing a miss. GOOD LUCK troubleshooting! It's always funner when someone else does all the hard work. But take note, none of my suggestions required you to spend any money. You don't see that often!

[img]/wwwthreads_images/icons/cool.gif[/img] MG48 - 88 Bronco
post #5 of (permalink) Old 01-18-2000, 02:54 PM
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Re: ignition problem

My 87 is fuel injected (5.0). I should have mentioned this earlier. It is not the plugs or wires. If I mash it from a stop, it will not do it. It is only when I am moderately accelerating. It will sort of "pop" out of one pipe.

post #6 of (permalink) Old 01-18-2000, 05:09 PM
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Re: ignition problem

I had the exact same problem. It would misfire at the exact same RPM range under moderate acceleration and it also went away when I mashed it. I replace the spark plugs and wires. It went away after that. Just an idea.

post #7 of (permalink) Old 01-18-2000, 05:37 PM
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Re: ignition problem

Some good info there! Saw a problem like that on a different vehicle once. About 5k miles after Platinum plugs were put in (didn't come with Platinum), would miss and sometimes stumble under light acceleration, like after turning a corner, for example. Could hear some pops in exhaust system then. Wires OK. Plugs changed to same make and number as what came in it, no more problems ever.
I think mg48 is right on the effective spark gap resistance versus rpm/light load.

About the "pops"... What I have concluded over the years, is that if you hear a "popping" in the exhaust, it's usually that one or more cylinders probably had a decent mixture, but didn't fire, and then lit up rather poorly in the ex. manifold or pipes due to the heat. And that the reason it didn't fire was ignition problems, whatever they were. So it seems if it really is only popping on one side, then something that's not common, that's on that side is suspect, like mg48 was getting at. Then again, maybe the side that's not popping, is getting real close to doing it too!

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