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A. Penland
A. Penland, Ford Senior Master Technician, ASE
Category: Ford
Satisfied Customers: 6212
Experience:  ASE Master Certified, ASE Advanced Gasoline Engine Performance
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We have a 2006 Ford Expedition with P0301 and P0303. We

Customer Question

We have a 2006 Ford Expedition with P0301 and P0303. We changed out the wires and plugs. The P0303 is gone but even after cleared repeatedly, the P0301 comes on and the car goes into "limp" mode for just a few seconds with the Check Engine Light flashing. Then as I accelerate, it clears, and then starts again. I can get it up to 85 and then it clears up.
Submitted: 1 year ago.
Category: Ford
Expert:  A. Penland replied 1 year ago.

Are there any ticking noises on the passenger side of the engine while it is idling and missing?

Customer: replied 1 year ago.
No.
Customer: replied 1 year ago.
Idle seems smooth, seems to be running well. Nothing else unusual.
Expert:  A. Penland replied 1 year ago.

Ok. Swap the coil and then the spark plug between cylinder #2 and see if the code changes to #2 cylinder. If it is still #1, it could be a bad injector or a rocker arm (Ford calls them followers) fell off.

Customer: replied 1 year ago.
You wouldn't think anything was wrong with it at all until I pull out of the parking lot and start to accelerate at medium pace. Then the light starts flashing.
Expert:  A. Penland replied 1 year ago.

Your engine has three valves per cylinder. If a follower fell off, you wouldn't notice it till you put a load on the engine.

Customer: replied 1 year ago.
We had swapped them earlier and still the P0301 and now we have a new one P0351 as well.
Expert:  A. Penland replied 1 year ago.

The P0351 is a coil driver failure for cylinder #1. Where are you getting the coils for your engine?

Customer: replied 1 year ago.
These came from autozone
Customer: replied 1 year ago.
Duralast. We've not had issues in the past.
Expert:  A. Penland replied 1 year ago.

Ok. Use a test light and disconnect #1 coil and start the engine and check for power on the RED wire and a pulsed ground on the other wire in the connector while the engine is running.

Customer: replied 1 year ago.
Done. The RED wire has power and the other wire has a pulsed ground.
Expert:  A. Penland replied 1 year ago.

It could be a bad coil. I do not recommend the aftermarket coils. But you have to use what you can afford and I completely understand that. Take one of the coils back and get a replacement one. Then retest the system. If the codes return, especially the P0351, the PCM (Engine Computer) will have to be replaced. The coil drivers are built into the PCM.

Customer: replied 1 year ago.
Actually now that I am sitting in the vehicle again with the key on and engine off, I do hear a faint clicking like tick-tock-tick-tock just on the passenger side.
Customer: replied 1 year ago.
We still have the P0301, but not the P0351 now. We swapped another coil we believe to be good. We are now going to take the one that we think is bad and put it on another cylinder.
Customer: replied 1 year ago.
What does the clicking noise mean?
Expert:  A. Penland replied 1 year ago.

Does the noise change when you change one of the settings on the AC controls?

Customer: replied 1 year ago.
Will check, but we just swapped out the #1 coil with the #5 coil, cleared codes and the P0301 came right back on after putting it under load. That is the only code.
Expert:  A. Penland replied 1 year ago.

You might want to swap the injectors between #1 and #2. You could have a slightly clogged injector. Swap them before replacing it.

Customer: replied 1 year ago.
We cleaned the injectors to start with, but ok. Also, the clicking noise remains with engine off and key on and does not change regardless of the a/c setting from on to off, change the mode, defrost on/off, etc. Stays constant.
Expert:  A. Penland replied 1 year ago.

It could be an electronic mode door motor for the AC system. Fully open the glove box and get the clicking noise to start and check the motors around the evaporato case under the dash. You will feel the clicking noise from one of the motors.

Customer: replied 1 year ago.
Ok, well that's secondary. Right now we just want to get the coil/spark/injector problem resolved. We are swapping 1 & 2 and I'm going to go drive it on the freeway and see what happens.
Expert:  A. Penland replied 1 year ago.

Ok. Just reply back when your ready.

Customer: replied 1 year ago.
Changed 1 and 2. Still the same P0301 code.
Expert:  A. Penland replied 1 year ago.

Check for power and ground to the injector the same way as the coil. See if you get constant power on the Red wire and a pulsed ground on the other.

Customer: replied 1 year ago.
Morning. We did the check on #2. And yes we have RED and pulsing ground. The engine is fairly new (factory Ford engine). Still only code is P0301.
Customer: replied 1 year ago.
Here's something else we noticed...we just replaced both dowstream O2 sensors as well and now we took it for a long test drive on the freeway with the ODB2 reader. On the live data, the STFT on the downstream sensors stays constant at 99.2% and doesn't change. Is this looking more like the PCM? We do seem to replace more of those than we should. Thanks
Expert:  A. Penland replied 1 year ago.

I have done a few also. But getting 99% constant is odd. You may want to check the converters also for that bank.

Customer: replied 1 year ago.
Ok, so what is the next step you recommend for the P0301 code we are still getting? We checked for the Red/Constant Pulse on #2 and that is also correct.
Expert:  A. Penland replied 1 year ago.

I would do a manual compression test on the engine and compare the readings to#2, 3 and 4.

Customer: replied 1 year ago.
Why 2, 3, and 4 when the code we are getting is for 1? I'm trying to learn also during this process :) Thanks
Expert:  A. Penland replied 1 year ago.

Sorry, I meant to do a manual compression test on #1 and then do that entire side and compare the readings. This will evaluate the mechanical parts of the engine without taking it apart.

A compression test will check for sticking valves and bad piston rings. The compression on each cylinder should be 175 psi.