97 f150 4.6 4×4…check engine light flashing

We don’t guess and throw parts here.

I countered this problem on my 98 F150 4×2 but only happens every time I step hard on the throttle 3-4 consecutive misfire. I solve the problem by replacing the faulty thermostat which is partially stuck at open position.

[b]Check engine light is only flashing several times but don’t stay on?
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After few months I encountered the same problem again which is cause by defective degas bottle cap.

I

[quote=”slotcar” post=82244][quote=”Raistian77″ post=82174][quote=”slotcar” post=82169]:( In the past I have read that when the check engine light flashes it means that the system is going to fail. [/quote]

Not really, a flashing check engine light means that the PCM has detected a misfire bad enough to damage the catalyst in the converter (in a short period of time), this is called a misfire Type A. The PCM shuts down or severely limits fuel in the injector for the missing cylinder to attempt to prevent this damage. A solid check engine light related to a misfire indicates a misfire Type B, this is a misfire bad enough to allow the engine to violate Federal regulations at the rate of 1.5 times the legal limit. A type B misfire is not bad enough to cause catalyst damage (in a short period of time, a Type B misfire still does do damage, but over a much longer period of time) The flashing is to let the driver know that the misfire is that bad and needs to be dealt with very soon as engine performance and longevity are diminished in this state.

The reason a Type A is so bad (besides pollution) is raw fuel dumped into the catalyst can ignite in the converter and cause some serious damage and in the older cars that did not shut off the injector cause the car to actually catch fire and burn down.[/quote]

🙂 Thank you for clearing up my knowledge on this problem. I knew it was a more serious problem, but I never knew the meaning of the differences in the check engine light.[/quote]

Not a problem slotcar, I blame the manufactures for allot of misunderstanding on how these things work. The manuals usually are very vague on warning lights and all seem to end with “have it towed to your dealership” if they took time to explain WHY more customers would understand why it should be repaired right away.

Before you replace the intake gasket make sure the heater hose connections are not leaking above #4 cylinder. It’s a known problem with your truck.

[quote=”Wolvez” post=82369]You just need a multimeter to check the Primary & Secondary Resistance of the coil.
Primary is 0.3 – 1.0 ohms
secondary should be between 6.5 – 11.5 ohms

Both test should be done with the IGNITION OFF
The primary is where the harness is connected. If you have a V8 connect the positive probe at the center, Left and Right are both negative. The resistance on both side should be the same.

You can check the Secondary Resistance by probing the paired cylinders where the spark plug wire is connected.[/quote]

Wolvez, ohming a coil only can point to opens in the winding, due to the nature of a transformer resistance measurements are useless. There just is not enough current in a ohm meter to actually load test the winding which has to be done to determine pass/fail of a coil. The failure point in most coils is the substrate insulating the primary and secondary winding and will only show up when the coil is stressed and the windings are saturated. What usually happens is the heat and vibrations cause cracks in the substrate and winding that only become a issue when the coil is saturated and the electrons are more likely to find alternate paths to ground. The path through open air (spark plug) is extremely inefficient and the electrons are more than happy to take a shortcut to get back to ground.

The best way to test a coil is with either a megger (very expensive HIGH current ohmmeter, kill you high) or a spark tester which will load the coil.

[quote=”Wolvez” post=82625][quote=”Raistian77″ post=82602]

Wolvez, ohming a coil only can point to opens in the winding, due to the nature of a transformer resistance measurements are useless.

The best way to test a coil is with either a megger (very expensive HIGH current ohmmeter, kill you high) or a spark tester which will load the coil.[/quote]

It’s really useless if the system has a Distributor. If I’m not mistaken we are talking about a Distributor-less Ignition System that has One Coil Per Cylinder.][/quote]

Does not really matter. A transformer is a transformer. In fact there really is no difference in design, a COP design just uses one coil per cylinder, the design of the coil is unchanged.

As current flows into the primary winding attached to the ignition system a magnetic field forms around the primary windings, with no path to ground the coil saturates. When the ground is connected, current flows and the field collapses inducing a voltage in the secondary winding. Since the winding ratio is setup that there is more secondary winding than primary windings the voltage induced in the secondary is much higher than the input voltage to the primary. Since there is a trade off, you sacrifice current for voltage.

The problem with a ohm test is that it can only test for direct internal contact shorts to ground or opens in the windings. In reality coils rarely fail this way, normally the failure is voltage leak. Coils are made by wrapping resin insulated thin gauge copper wire (primary)around a winding of thick gauge copper wire (secondary) around an iron core (to intensify the magnetic field) than dipped in a resin to insulate the assembly (old coils used oil to insulate and cool them). After years of hot/cold cycles the resin begins to break down and the electrons find shortcuts to go either to the iron core or the neighboring coil (in a coil pack) these faults will usually only show up when the coil is stressed or under a heavy load and the highest potential exists for the electrons to try and find an easier path to ground. So ohming a cold coil that is not carrying any current really wont tell you much other than if the winding in intact or not.

I have taken out bad coils that would fail under a load and ohm them and find the numbers to be in spec almost every single time. The reason coils fail most under a load (heavy acceleration) is the conditions in the chamber actually make it harder to jump the gap with a spark as the air is very turbulent, the coil has to “work” to find it’s path to ground. If there is ANY easier way to get to ground the coil “cheats” and you have a misfire.

The reason resistance testing became so popular is that originally a coil test involve both ohming the windings for shorts to ground (which were common in oil filled can coils) and stress testing the coil. Problem is many techs just do the resistance test and not the stress test and often fail to diagnose a bad coil. Funny thing is the resistance test is not needed, ever. If you have a short in the coil or an open a stress test will reveal that. If a coil fails to fire a spark tester (cant use a grounded plug the voltage requirement is way to low in open air and will not mimic the conditions inside the combustion chamber) all you need to test for is 12 volts going into the coil and a pulsing ground. If you have both, the coil is bad and needs replacement.