odd noise

[jorton]

99 f150 v6 auto
This is the only topic I found that matched my trucks odd noise. http://theoildrop.server101.com/ubb/ultimatebb.php?ubb=get_topic;f=24;t=000865#000000

I've been listening to it for 3 years. This noise is odd because cold start-up is always quiet. I hear a low pitched snapping sound when creaping up my driveway at normal op temp. Or anytime at low speed, low RPM at normal op temp. Never when cold.

If anyone has heard something like this before I'd sure like to know what it is.

Thanks, Joe

 

[ZR2RANDO]

I think I'd set the parking brake, nudge the front bumper against a tree (with an old tire for a rub bar), and put big logs in front of all 4 tires...but you're on the right track. Maybe you can at least isolate it to top or bottom, left side or right side.
Looking forward to the diagnosis.
Rando

 

[labman]

Check tight spots. With a warm engine, the mounts be be giving enough to allow contact.

I had an 81 Phoenix that died if you let the clutch too quick in reverse. With the hood up, and my son watching, he spotted sparks under an engine brace. The engine moved just enough to wear through the insulation of a wire on the underside. Just use your brakes and let the observer stand to the side.

 

[ZR2RANDO]

He has a helper? Well that certainly makes it easier

 

[ZR2RANDO]

I can tell the motor in one of our vehicles (S10 Blazer w/4.3 gets noisier after oil warms up. Thicker oil always quiets a motor to certain degree. I can also tell the injectors are noisier after warmup too. You may want to do some poking around with a mechanic stethoscope (long metal listening device..

at idle and locate just where the noise is actually coming from. It may surprise you.
Good luck
Also check the spark plug connectors, I had a loose plug once that made a snapping sound, but only after block warmed up.

 

[jorton]

To do that I would have to have the truck in D with the parking brake on and raise the RPM just a hair in order to make it do it.

I have done that before but without a stethoscope. I replaced the exhaust manifold gasket but it wasn't that.

It could be 1 injector, because the frequency is slow.

 

[TheLoneRanger]

quote:

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I hear a low pitched snapping sound when creaping up my driveway at normal op temp. Or anytime at low speed, low RPM at normal op temp. Never when cold.

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A snapping sound can be caused by a high tension spark, such as from a coil-on-plug shorting out or a plug wire shorting. (This won't necessarily cause a misfire, if the spark is jumping across a loose plug connector.) An exterior spark can usually be seen by looking at a running engine in the dark. It would also be more pronounced when the engine was warm and electrical resistance was higher......

 

[jorton]

Ok I have some good ideas to try next time I have a helper. Check for arcing at night, and listening with a stethoscope.

Thanks for the advice!

Joe