Basic Spark Plug wire question

[65fback]

My 200 has been missing some at idle for a while and recently it's started feeling like it's missing at speed at well. I've been meaning to get down to Gene 2dr to help diagnose but it's either been too nasty to pull the car out or work has been busy crazy and just haven't been able to get over there.

Today is a nice day (albeit cold with a windchill to throw in!) so I pulled the car out to check the tire pressure, run it for awhile, and see if I could find the source of the miss. I started pulling spark plug wires. The first one I pulled gave me a nasty shock. These are supposed to be insulated, right? I was getting a shock from the boot. If I move my hand back along the wire I don't have the problem so much. I didn't seem to notice this on the other wires.

I'm still kinda new to all this, but I shouldn't be able to get a jolt through the wires, right? Could bleed through of the electrical charge be causing my miss? I don't know how old the wires are. The car was running OK when I bought it so I didn't go through the ignition system.

Oh, and pulling the wires one by one didn't give me a culprit. Car ran worse while each wire was off.

 

[FalconSedanDelivery]

Generally you should NOT be shocked by just touching the wires , if you are the wires are bad or there is so much resistance at the spark plug its looking for an easier path to ground

 

[bubba22349]

X2 you might try a new set of wires along with a cap and rotor all are easy to change.

 

[rbohm]

8) i agree with the others in this. you should be able to pull the plug wires without getting shocked. the nice thing however is that at least you know that its not another problem in the system where voltage is not getting to the plugs. replace the wires with some good ones.

 

[ludwig]

The Schjeldal boys have a test for current leakage in the I6 although it's probably good for all the others too. You observe the plug wires in the darkest dark of night to see if there is a blue glow or arcing. You could even poke around in the dark with a metal rod and see if you can induce some arcing. But that is just boy science.

The insulation deteriorates over time and between dust, dirt and other contamination, a path for current to escape the jacket and flow to ground (engine block) is entirely possible.

 

[FalconSedanDelivery]

That Test was around way before the above mentioned boys , but it is a cool test , works even better if you can get another person to help , you put it in gear and with a firm foot on the brake ( Automatic cars only of course ) bring up the rpms to put a good load on the engine , it will show where there is a marginally good area real quick ,

 

[ludwig]

That Test was around way before the above mentioned boys

You mean, poking something dangerous with a metal stick? That has been around as long as there have been boys. Happy to say.

 

[170-3tree]

I think there was a similar test in which you'd put on washer fluid on the wires and if they were bad they'd glow blue or something.

 

[chad]

I think there was a similar test in which you'd put on washer fluid on the wires and if they were bad they'd glow blue or something.

Just lookin under the hood at nite in that area can C an arching spark if that bad a condition.

The fluid idea may B: a lill 1 X spray of any water (not just washer fluid) makes a ground, and that can B observed (but not as a 'glow') for arching spark ("flashin lights").

If U had a wet hand & some water dripped onto the end of the boot it could have made you the ground thru which...

I wouldn't use a metal rod, dangerous. On the other hand -
The wife could grab it to see if there's still a loose spark. If U sleep on the couch that nite U know it's time to change THAT wire.

 

[ludwig]

It would take you most of the week to find all the bad wires. I'm thinking maybe two wives as well.

 

[chad]

...or 6 wives.
Trouble w/dat is the odds go up enuff that I might see "flashing lights" (1 of them may pop me up side'a da head) when NOT lookin under the hood.

Nuff jokes, U change the wire yet, 65fback?
U can get a wire at the big box auto store, cut to length, press on the proper ends or if richer than me, put on a whole new set (3rd - I think we have it wire by wire as an intermediary step if wanted).

 

[ludwig]

Adequate is about $20; Good is closer to $35. Worth the extra, I think.

 

[chad]

a "good" set last 10 yrs. Ludwig?

Any name brand to select in that price range?
Recommended "style"? /OR/ type of boot, etc?
(one, I think is called 'spiral wound'?)

Thanks-

 

[ludwig]

Far as I know, my good set lasted 40 years. That's what was in there when I got the car. I got 'stock' from one of the Mustang houses about 8 years ago and no probs. I was going for the 'stock +' look. Looks like stock but works better. Sure. Good will last 10. I would go aftermarket now. Colors n' style because my tastes have changed.

You want to make sure they are suppressor rated so the radio doesn't hum/buzz.

 

[65fback]

Uh, let me see. I think I'll..... change the wires!

Thanks everyone. I thought that was the case but find it's usually a good idea to ask first when you don't have much recent experience with old cars. I'll do the cap and rotor too for good measure.

 

[ludwig]

Plus, you don't want to miss out on the wisecracks and idiot speculation that hitches a ride.

 

[chad]

"...cap and rotor too..."
All right now! Let us know how it goes after
(any more unusual occurrences)...

"...that hitches a ride..."
we can have fun, too, no?

"...set lasted 40 years..."
thasss mine (actually 30), didn't think any 1 would be as
frugal as me - but they still wrk fine so mights well...