Ford Repair Questions? Ask a Mechanic for Answers ASAP
They probably did not replace all the coils because they cost between $50- $80 a piece, not including the spark plugs. You'll need to have the remaining coil on plugs (COP) tested. When they start to fail, they generate radio frequency interference that becomes induced into the wire harness of your truck. The different circuits of the wire harness sees this electrical noise and causes the engine computer (and other computers) to act up. There is a service bulletin from Ford to stress test each COP using the Ford WDS or IDS. The problem on your truck is very common on other Ford products using a COP ignition system.
This article supersedes TSB 04-16-01 to update the vehicle applications and model years.
Approximately 50% of coil on plug (COP) coils returned for warranty do not have a problem.
The misfiring cylinder must be identified through Self-Test misfire codes or through WDS Power Balance. Rule out base engine problems, rule out fuel problems, and then look at ignition problems (be sure to rule out coil primary circuit issues). Once the above steps have been completed, and the issue is in the secondary part of the ignition system, the oscilloscope procedure outlined in this TSB can isolate the difference between a coil or spark plug problem.
The optional WDS COP Kit available through Rotunda will provide more accurate diagnosis and help reduce replacement of non-defective parts. The Kit (418-FS528) can be purchased through 1-800-ROTUNDA.
The following material will detail the diagnostic steps on WDS to take the guesswork out of misfire diagnosis using the COP Kit. The following procedure is for cylinder specific misfires and not random misfires. Random misfires have a different root cause and are not covered by this TSB.
Misfire Definition: A misfiring cylinder is lacking power relative to the other cylinders. The causes for a cylinder specific misfire could be fuel, spark, or mechanical problems.
Perform a thorough visual inspection. If no visible concerns are found use the following WDS tools for misfire diagnosis:
If there is a self-test code identifying a particular cylinder then you just need to determine if it is a fuel, ignition, or possibly a mechanical problem. Proceed to Step 2 after running Relative Compression to rule out any mechanical issues. If there is no self-test code and the customer concern is a miss, proceed to Step 1.
The cylinder specific miss has to be identified as shown in the example in Figure 2 in order to proceed with the remaining steps. If the miss does not occur at idle (in the bay), try to brake torque the engine. This extra loading should reproduce the miss in the bay. If the miss cannot be reproduced during brake torque, select Relative Compression under Powertrain on WDS before going on a road test to rule out mechanical problems. If Relative Compression shows a problem then the base engine issue must be serviced. If Relative Compression results are good (Figure 3), road test under as many different driving conditions as possible until the miss occurs on Power Balance. Some misses may be very intermittent so be patient and concentrate on steady load conditions. Once a cylinder dropout is identified proceed to Step 2.
Run Fuel System Test on WDS to determine if there may be a fuel problem. After completing fuel Pressure/Leakdown test, select Injector flow to isolate a restricted injector as shown in Figure 4. If all the injectors are within specification, proceed to Step 3.
Run Ignition System Test on WDS to determine if there is an ignition problem. Look at both duration (DUR) and kilovolts (KV) and look for values that standout from the rest as shown in Figure 5 and Figure 6.
If either spark duration or peak KV on the Red Probe (Suspect Cylinder) are offset from the values displayed on the Black Probe (Known Good Cylinder) then the problem is in the ignition system. Rule out coil primary circuit issues before proceeding to coil secondary issues such as the spark plug, coil boot, or possibly the coil. Use the WDS Oscilloscope with the COP kit to determine if the issue is the coil or the spark plug.
No problem, I was skeptical when I first saw this TSB, but it fixed allot of weird problems I had. Especially on Lincoln LS's.
Here is the rest of the service bulletin, it shows the diffrent displays and tests on the Ford WDS/ IDS.