Waste Not Want Not

Michael Mobile Technician Clinton, Utah Posted   Latest  
Case Study
Driveability
2004 Ford Taurus SEL 3.0L (2) 4-spd (4F50N)
P0305 — Cylinder 5 Misfire Detected
P0302 — Cylinder 2 Misfire Detected

I went over to a shop that had an issue with a Ford Taurus. They said it had a misfire and they had changed the coil three times. The spark tester showed weak spark. They wanted to change the computer but none were available. I asked them to wait on the computer so I could verify that it had a bad coil driver. I hooked up the labscope and the primary side looked close to normal. It was pulling to ground like it should. After accessing the situation I saw that the ignition wires were original. I suggested that the wires and plugs be changed to see what it would do.

Why would I suggest this? The key is in the "Waste Spark" system. I still can't get my head around how it does not fry electronics but here is how it works,,. The high voltage moves from one side of secondary section of the coil, through the first spark plug, through the block, then through the companion spark plug and back to the coil. If there is high resistance or a short in the system, the spark for one or both plugs will be effected. One plug fires from ground to electrode and the other from electrode to ground. The customer called me back this evening. They said that they changed the plugs and wires. The misfire is now gone. Below is a training video from Autolite. It has some great info on Waste Spark systems.

youtube​.​com/watch?v=9TqB76…

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Geoff Diagnostician
Lahaina, Hawaii
Geoff Default
 

Was everyone at that shop too young to know about spark plug wires?

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Eric Owner/Technician
Edgerton, Wisconsin
Eric Default
   

Just because you see them on a weekly basis doesn't mean the rest of the states haven't moved on. Next you'll be telling me diesel injectors used to be all mechanical, what an imagination you have. ;-)

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Geoff Diagnostician
Lahaina, Hawaii
Geoff Default
 

I didn't figure it was possible to forget that domestic OE plug wires don't last 15 years, so I guessed everyone at the shop was 35 or under. We have, however, learned that on old coil-pack Fords here, that if the plugs were at .080" and wires were original when it started misfiring, it needs a coil-pack too. So the story could have easily happened in reverse; (i.e. they replaced everything…

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Samuel Technician
Somers Point, New Jersey
Samuel Default
 

It is to our advantage to have been fortunate enough to be exposed to the earlier days. This also helps us understand the changes.... We have commented before on different topics and how in a shop setting, it is good to have some old dogs along with some young pups. I can remember at the tail end of carburetors I worked in an emission repair shop. We shared the Sun machine, the old dog repaired…

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Geoff Diagnostician
Lahaina, Hawaii
Geoff Default
 

I sure wish there was still someone more experienced than me here (I'm 47). Nothing worse than having to learn for the first time how some 80's car, towed-in, works. At my last shop it was just like you said, the older guy did all that. I never dealt with pre-OBD2 until a few years ago. Now I am the guy who is stuck learning ancient history. My MTS 3100 (that I just got four years ago) is in FAR…

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Randy Diagnostician
Glendora, California
Randy Default
 

Yep the 80 s good times for diag I had to purchase ecm break out boxes for just about all cars to git any data . And still use them from time to time .

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Jim Mobile Technician
Southampton, Pennsylvania
Jim Default
 

My wife and I have close friends that recently retired over there from the Philly area and love it, They are trying to talk my wife into us going over there and retiring. I'll bring all of my Pre OBD II equipment with me. :-)

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Randy Diagnostician
Glendora, California
Randy Default
 

You will use it no rust here . Not un common to work on cars over thirty years old here

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Geoff Diagnostician
Lahaina, Hawaii
Geoff Default
 

Sweet! I'll give the SW your number. :-)

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Randy Diagnostician
Glendora, California
Randy Default
 

If you need help on pre obd 2 pm message me will be glad to help

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Geoff Diagnostician
Lahaina, Hawaii
Geoff Default
 

I appreciate that, thank you.

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Randy Diagnostician
Glendora, California
Randy Default
 

One old guy just trying to helping out . 40 plus years . Ha ha

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Matthew Technician
Caledonia, Michigan
Matthew Default
 

Very good information, especially for us newbies on this site with passion for the auto insustry. This is the kind of information i look for from the senior techs in this industry.

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Randy Diagnostician
Glendora, California
Randy Default
 

yep it is a ford

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Anthony Technical Support Specialist
Kirkwood, Pennsylvania
Anthony Default
 

Hi Mike: A few points that people may find of interest. As you saw, an open in the secondary will take out a cylinder. No great surprise there. A shorted secondary will take out both cylinders though. Years ago, Tim Lena posted a …e study. He had replaced the valve cover gaskets on a vehicle, probably a GM. (The only thing that I remember for sure is that it had to have been after 10am. He…

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Eric Owner/Technician
Edgerton, Wisconsin
Eric Default
 

Guido, I remember those wasted ignition systems very well, I still have one wander into my shop once in a while but most have succumbed to the effects of road salt. I also remember what happened when someone who didn't know better replaced the spark plugs with a single platinum set. When their error was pointed out they would argue that single platinum was what was in there originally. For a…

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Michael Mobile Technician
Clinton, Utah
Michael Default
 

"Double Platinum plugs?, they are $5.99 each! Just throw in some standard plugs, they are only $1.99, they will work just fine."

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Geoff Diagnostician
Lahaina, Hawaii
Geoff Default
 

One pink. One turquoise.

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Geoff Diagnostician
Lahaina, Hawaii
Geoff Default
 

Guido, email me with the secret identity of the "Boy Wonder". I have clearance from Commissioner Gordon.

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Jim Mobile Technician
Southampton, Pennsylvania
Jim Default
 

Brandon Steckler

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Geoff Diagnostician
Lahaina, Hawaii
Geoff Default
 

Thanks, Jim, my guess would have been Mario, who really started churning out the videos after he got your old scope. Fun to see people enjoying the field still. Would be neat to live where customer's owned something other than a junkyard fugitive....here it does not matter which valve is leaking, the car is toast. (not that I am leaving here...EVER....I enjoy just reading and chatting now).

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Jim Mobile Technician
Southampton, Pennsylvania
Jim Default
 

Very Good information, Guido. I would like to add that it wasn't uncommon to still have a misfire on these systems even after replacing spark plugs and wires. What would happen sometimes with a defective spark plug wire was the energy would build a carbon track "Back Home" and Home meaning the Ignition coil, hence the reason we would also find the Ignition Module damaged of the systems like GM…

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Anthony Technical Support Specialist
Kirkwood, Pennsylvania
Anthony Default
 

Hi Jim: With the Grand Nationals and T-Types, wire issues were common on the turbo side of the engine. (These were all my customers from Trinidad & Tabago would drive. The difference was in how much money they had.) It's been too many moons. I don't remember if I knew about the coil circuit issues. I could've been just lucky. It explains the accelerated electrolysis. IMO, Gen 1 was changed…

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Samuel Technician
Somers Point, New Jersey
Samuel Default
 

WOW....memory lane referring to the GM setup ....I immediately thought of the, what were they, the 3.4 and the 3.8?....coil pack on top of the module...the tracking, the heat and many times both causing a severe misfire or when hot a no start condition....good times!

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Jay Business Development Manager
Shelby Charter Township, Michigan
Jay Default
 

I made that video almost ten yrs ago, nice to see its still help folks out.

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