1998 Ford Expedition Running Rough

Hello,
1998 Ford Expedition 5.4L

This is a relative's vehicle I took a look at while over for Sunday lunch. It has P0354 code plus three more corresponding P035_ codes for three other coils. Testing the control wires for several coils the wire is not being grounded.

Now my question. Assuming the wiring between the coil and computer is good can this only be a faulty pcm? Doing some research after leaving I see this engine has two camshaft sensors. Is it possible for one to fail and lose spark to half the cylinders? There was no camshaft codes. The only other code was for the IAC. Guessing this may have been because the idle was too low running on 4 cylinders.

Is it possible for this to be a computer ground issue if half the coils are still being controlled?

I am not a pro and don't want to guess. It just seems a little odd four would fail at once since it seems they are all controlled independently. Is this common? Just fyi it does have two Accel replacement COP units. One is being fired the other not.

Is there a limp mode where it would shut off spark but not fuel. The exhaust smells bad plus it has the coil codes so I assume it would not set those codes if the pcm was deactivating the coils.

One other thing is it common for a bad COP to kill the driver in the pcm?

Thanks for any help possible. This is a great resource.

I’d check powers and grounds at the pcm. Also try putting a mood light in the coil connector clear codes crank engine see if it pulses which I’m guessing it won’t. If it pulses then turns on I’d say it’s intentional shut down which I think this car is to old to have.

Definitely agree with Cheryl about the noid light suggestion. If it pulses, then that suggests a good PCM driver and wiring. Electrically open coils can cause this code, same as a wiring or PCM problem. Speaking of, keep an eye out for loose connectors (with broken retention tabs) or broken wiring inside the insulation very near the connectors themselves. I've seen both.

Mike4799 wrote: Now my question. Assuming the wiring between the coil and computer is good can this only be a faulty pcm? Doing some research after leaving I see this engine has two camshaft sensors. Is it possible for one to fail and lose spark to half the cylinders?

Not that I'm aware of. If that were possible, I think it'd depend on which cylinders were coding.

Is it possible for this to be a computer ground issue if half the coils are still being controlled?

Again, not that I've seen, but possible? I'd be good practice to check all PCM powers and grounds before replacement.

It just seems a little odd four would fail at once since it seems they are all controlled independently. Is this common? Just fyi it does have two Accel replacement COP units.

For them all to fail at once would definitely be uncommon. :lol: There could also be several different issues at work, depending on how recently someone else has been under the hood.

One other thing is it common for a bad COP to kill the driver in the pcm?

Very common. :silly: Less so on these older trucks, in my experience, but still common. In the cases that I've verified a failed driver, the truck got all coils, plugs and a PCM.

If you haven't seen it already, this case study video is right up your alley.