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SuperBob, Ford Senior Master, Mazda Senior
Category: Ford
Satisfied Customers: 2609
Experience:  18 years Ford, Lincoln, Mercury, Mazda Dealer ASE master, diesel certified. Specialize electrical
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2004 F-150 5.4 Triton 3 valve Replaced timing chain, tensioners

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2004 F-150 5.4
Triton 3 valve
Replaced timing chain, tensioners & guides


Now runs rough.
If I unplug the cam positioning sensor on the right side it idle smooth.

Switched the left and right sensors and problem remained on right side.
(not sensor)

Making the assumption that need to replace the Variable Cam Timing mechanism.

Is there any other potential problem?
HelloCustomer if the truck was running fine before the repair, it sounds like you may have the timing chain off time by one tooth on the cam sprocket. When the cam position sensor is unplugged the engine will rely on the sensor for the other side of the engine and guess when to fire the injectors and coils for the side that has no sensor, when you plug the sensor back in, you are telling the injectors and coils to fire at the actual position that the cam is in instead of where the computer thinks it should be.
Customer: replied 7 years ago.
We took your advice when replacing the timing chain. We used vise grips on the cam and marked everything. All of the marks lined up when we assembled them.

On the right side however when we took off the chain the VCT seemed to ratchet. Could it appear that the marks lined up but in reality they did not?

Ok, I remember you. give me a few minutes to review the previous thread to refresh my memory


Any thing is possible, it is also possible that because the tensioner was compressed during the repair and had no oil pressure in it upon the first few cranks of the engine after the repair that there was enough slack in the chain that it could have jumped a tooth before the tensioner had time to build pressure to hold the chain tight.

That ratcheting type noise you heard when you took the vct off was the chain sliding over the teeth on either the cam sprocket or the crank sprocket, I assume you had already marked the teeth to chain locations on both the cam and the crank sprockets?

Customer: replied 7 years ago.

Everything was marked prior to that point.

If you lined it all up just the way you took it apart, then the only logical explanation is that it jumped time before the tensioner charged up. I wish I had an easy way to check it, but the only way you can, as I am sure you are aware is to take the cover off again. If it wasn't for the potential of the spark plugs breaking I would advise you to pull all the plugs and crank the engine over several times to charge the chain tensioner so the crankshaft has less turning resistance when and if you have to take the timing chain tensioner off again.

Ford dealers have a wedge on a thin steel handle that can be installed into the space between the timing chain to hold the chain in place for replacement of the vct sprocket without removing the front cover. If you get your crank mark on tdc, you will be able to (with this tool) move the sprocket by one tooth if you can tell that it is off by visually comparing it to the workshop manual.

Customer: replied 7 years ago.

Can pull off the cover pretty quick now so will do it that way.

Thanks a lot for the help.

In the future is it possible to request you specifically?

Yes, you should be able to on the pull down menu when you ask a question.

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