Okay guys. My 02 is giving me the run around with a knocking sound. Everyone swears it is an injector stuck open and what I am hearing is fuel knock (loud). I have done a lot looking to fix this sound. I can unplug the #3 injector and the sound goes 70% away. Unable to really hear if from an open valve cover or the top of the motor but can hear it from the wheel well. Plug it back in and the sound comes back to full volume. It seems like I have narrowed to cyl #3 but NOT the injector (replaced it anyway...twice). I don't think it is loud enough to be a rod knock (doesn't sound like someone hitting the engine with a hammer...) What can be my problem when there is combustion the noise is louder than when there is no fuel being added to that cyl???? Anything will help. Probably have tried it but?

 

Hi dburress and welcome to FTE.

What engine are we talking about here?

One thing comes to mind (if you have a gas engine) is maybe you have an exhaust manifold leak due to rusted studs?

 

Who is everyone that is telling you there is an injector stuck open? Injectors that stick open tend to do some damage. Having 3 injectors in a row stick open in the same hole is pretty rare.

With you issues with #3, I'm wondering if you have a 7.3? The recall CPS Ford used caused some issues with the #3 & #8 cylinders. How loud is your knock when you don't unplug the injector?

Tell us which motor you have and we can offer more specific advice.

 

thanks for the reply. I do have a 7.3. The Ford dealer did a elimination test the 1st time and told me #3 quieted the sound when they dropped it out so I replace the injector and no change. I pulled the valve cover and unplugged the injector and a lot of the sound went away. Not all of it. Something is making the sound louder when there is combustion in the cylinder. When no fuel is fed to the cyl it is a lot quieter. The know is like a LOUD injector knock. Nothing like a connecting rod bearing going out or anything like that.

I am wondering if there is a bad lifter? if there is no combustion maybe lifter doesn't have to work as hard to open a valve??? I am running out of ideas.

Don

 

To find out if it's an injector, take your truck and get it up to 50 mph or so where the torque converter is locked. Preferably find a down hill grade and take your foot off the accelerator.

During deceleration with the torque converter locked, the IDM will shut down the injectors and your noise should go away if it's injector related. If the torque converter is unlocked, the engine will just return to idle when you take your foot off. (This test works at slower speeds with a stick shift)

 

I have done that and the knock is still there. Am convinced it is not injector related. I am now looking at lifters or something lower in the head