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Ronnie
Ronnie, ASE Certified Technician
Category: Lincoln
Satisfied Customers: 33469
Experience:  35 years as an automotive tech
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I am having trouble with my 2005 Lincoln Navigator. The

Customer Question

I am having trouble with my 2005 Lincoln Navigator. The Cylinder on the drivers side which is 5,6,7,8 doesnt seem to be working. Tried everything, put in a new cylinder, new coils, new spark plugs (motocraft) and still the car keeps vibrating when on idle and more rough when on drive. The rpm keeps fluctuating between 1 and 2 when on idle and also when on drive with my foot on the brake.
Submitted: 1 year ago.
Category: Lincoln
Expert:  Ronnie replied 1 year ago.

Hello and thank you for your question,

Have you ran a compression test on these for cylinders?

Do you have power at the four coils on these cylinders on the red/lite green power wire?

Customer: replied 1 year ago.
i am actually not a mechanic but i was told that the power coming in on the four coils on this cylinder is low compared to the one on the passengers side
Customer: replied 1 year ago.
hello are you still there?
Expert:  Ronnie replied 1 year ago.

Yes Im here.

Can you take a volt meter and check the key on power at the four coils on the red.green wire for me?

Customer: replied 1 year ago.
okay i am on it now
Expert:  Ronnie replied 1 year ago.

Check the voltage with the key on and post back with the results and we can work fro there, also if you can see if a compression test was done on the four misfiring cylinder .

Customer: replied 1 year ago.
okay, thanks, ***** ***** back to you as soon as that is done...
Expert:  Ronnie replied 1 year ago.

Sure thing, Im here all day.

Customer: replied 1 year ago.
Hi im back, i have the volt meter with me now. What should i be reading?
Expert:  Ronnie replied 1 year ago.

With the key on you should see battery voltage at each coil on the red/green wire.

Customer: replied 1 year ago.
i am being told theres no earthing wire...not sure what that means....
Expert:  Ronnie replied 1 year ago.

The coils are fired by ground switching on the other wire, you need power to the green/red wire and the ground is provided by the PCM (computer) to fire the coil.

Customer: replied 1 year ago.
I am sending you a picture of the reading on cylinder 1 (i assume that is the one in front of the car at the passengers side). I want to know what it is i should look at for the reading
Expert:  Ronnie replied 1 year ago.

It looks to me like the meter you are using does not read 12 volts or your on the wrong scale. It need to be set on 12 volts before testing.

Customer: replied 1 year ago.
This is a picture of the meter, do i have it set on the right dcv?
Customer: replied 1 year ago.
I mean do i have it set on the right scale?
Expert:  Ronnie replied 1 year ago.

Yes that looks right scale, now you need to see 12 volts.

Customer: replied 1 year ago.
Okay i did that on all of them and this is the reading i got on all of them
Customer: replied 1 year ago.
On all the coils that is....
Expert:  Ronnie replied 1 year ago.

I cant be sure because its very hard to read your screen due to smudge but it looks like you have battery voltage. I'm thinking you have a bad driver in the PCM (computer) . The coils are fired by ground switching from the PCM, you can check to see if this is the case by taking a standard 12 volt test light and placing the test end on the power side of the coil and back probing the other wire and start the engine, if you have the ground switch signal from the PCM the light should flash, if it does not on all foue cylinder then that means the computer is likely the source of your problem .

Expert:  Ronnie replied 1 year ago.

I cant be sure because its very hard to read your screen due to smudge but it looks like you have battery voltage. I'm thinking you have a bad driver in the PCM (computer) . The coils are fired by ground switching from the PCM, you can check to see if this is the case by taking a standard 12 volt test light and placing the test end on the power side of the coil and back probing the other wire and start the engine, if you have the ground switch signal from the PCM the light should flash, if it does not on all foue cylinder then that means the computer is likely the source of your problem .

Customer: replied 1 year ago.
This is a picture of the PCM i have i n there right now; the PCM that came with it was 5L7A-12A650-LA and then after the spark plugs got changed (motorcraft), its been having this issue since then. I was told it was a PCM issue which was why i got the one in the picture. The vin for the car is 5LMFU28525LJ12677
Expert:  Ronnie replied 1 year ago.

If the PCM you replaced is working then the test light should flash at each coil with the engine cranking and or running, is the light flashing?

Customer: replied 1 year ago.
I am about trying that..... I will let you know once ive done that. Do i try this on all the coils like i did with testing for 12 volts?
Expert:  Ronnie replied 1 year ago.

You need to try it on the cylinders that are not firing meaning 5 6 7 and 8.

Customer: replied 1 year ago.
Hi Ronnie, the car seems to be running smoothly after changing all the Injectors and then i was driving down the highway testing it out when suddenly it lost power and wouldnt accelerate pretty much and then the check electronic throttle control comes up on the dashboard. What do I do? I read a few past answers on justanswer talking about the output speed sensor.... I cant even locate where that is. Please I need help. Thanks
Expert:  Ronnie replied 1 year ago.
Is the computer setting any fault codes? A speed sensor will not normally cause a lack of power.

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