How many times have you tried to find the misfiring cylinder on a Ford COP (Coil On Plug) ignition system without losing your mind?

2000 Lincoln LS

2000 Lincoln LS

Here is at least one way to find a secondary misfire with just a scope. Lets say you get a Ford COP system with the complaint of a check engine light and/or misfire. You get the vehicle and if the check engine light is on you retrieve a P0300. Where do you go now? What I do is feel the misfire out and try to determine by feel if it is the ignition system or not. An ignition misfire is usually sharper feeling then other types of misfires. I also scan the vehicle for codes and look through the data stream to see if anything looks out of place. If everything looks good, I then consider plugs and coil boots based on mileage and repair history. You don’t need to do an ignition tune-up for this to work but it is usually

2000 Lincoln Ignition Scope Capture

2000 Lincoln Ignition Scope Capture

needed and sometimes is the cause of the misfire. Ok, now the scan data looks good, no codes besides maybe a P0300 series code, and even the plugs and coil boots may be new. There is still a sharp ignition type misfire, what do I do? You can use mode 6 data and see what cylinder has the most misfires. This would be my back up, but I have seen this data telling a different story than I end up finding. One thing to keep in mind is mode 6 misfire data isn’t live, so beware. What I

2000 Lincoln LS Engine

2000 Lincoln LS Engine

do, is hook up one lead to the easiest to probe injector I can find. This will be my trigger which I will use with the vehicles firing order. Next, I probe the power supply/supplies for the ignition coils. You can now see the coils turning on and off from 0v to 14v. Some Fords have the multi-strike ignition system where you will see the coil fire up to 3 times in one firing event. With everything hooked up, I will then disconnect one coil to find its relationship to my injector trigger. Now I will do what has to be done to get the vehicle to misfire which may include; snap throttle, power breaking, leaning the engine out, or just waiting it out. If you have a secondary ignition problem, you will see it on the coil primary scope trace by the voltage spikes. If the coil primary circuit opens up you will also see this by the loss of a coil pattern, just like you did when you unplugged a coil . All that is left is to use the firing order, injector trigger, and primary coil trace to find the exact cylinder or cylinders with your ignition problem. I hope this saves all of you a headache in the future.

Leave any questions or comments below. Thank you.


Automotive Diagnostic Scope Training ManualThe Automotive Scan Tool, Scope, and Waveform Training Manual is just over 40 COLOR pages long and is full of images, tests, information, tables, conversions, and common problems. This manual is focused on advanced beginners and intermediate users. Advanced users would also find this manual very handy. The main focus of the manual is on scope usage, interpreting waveforms, and utilizing your graphing scan tool(s).

Great guide for Snap-On Modis, Versus, and Vantage Pro users but the manual is designed for all automotive scopes in mind. This great resource includes useful charts and tables, scope waveforms, graphing scan tool testing tips and tricks, along with scope test lead and low amp probe test hook up location diagrams. Sensor tests include O2, TPS, VSS, MAF, CKP, CMP and MAP. Other component testing includes fuel pumps, coils, starters, blower motors, and fuel injectors. Ford Mode 6 misfire diagnostics and Ford coil on plug (COP) testing tricks included. Tricks include two test lead hook-ups to diagnose how many coils and which cylinder coils are bad, even before the customer knows! Download Now – $15

Comments (9)

  1. Bruce Marzloff

    Great way to save time.i will be using it soon Glad i found your website. looking foward for more tips

  2. Doug

    great articles and book, i have a quick question are you able to check primary with normal leads or did you need to purchase special ones from aeswave.

    • Travis Dewitz

      On Fords I just do it with my normal leads. Any leads should work, the better ones just give you a cleaner signal. I have never had issues with the ones that came with my scope.

  3. John

    I have a 2004 Lincoln LS V6. The check engine light is on, with a code P0305, #5 cylinder misfire, along with code P0316, crank sensor. We have already replaced the coil, but the engine does not seems to have to the power it should have. Also there is a growling sound from the engine on acceleration. Does anyone have any ideas as to a solution to these problems?

  4. gina thompson

    Creative blog post ! I Appreciate the information ! Does someone know where I would be able to grab a sample IRS 8379 form to fill in ?

  5. An open or high resistance in the coil’s secondary windings will also cause a weak spark or no spark, and may also damage the ignition module due to feedback induction through the primary circuit.

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