Engine Knock

[The DB]

My 2000 Explorer with a SOHC v6 engine has developed a knock. It seems to be worst right at about 2500 RPM, and is somewhat intermittent.

Another issue that has been happening even longer is the on the dash, sometimes the seat belt light comes on for no apparent reason and the tack drops to 0 rpm for a minute or so. I think that is a problem with the wiring for the display, but am not 100% sure on that.

All regular maintenance has been done. Is there anything I should look at or try before bringing it into a shop?


The DB

 

[deweyville65]

My 2000 Explorer with a SOHC v6 engine has developed a knock. It seems to be worst right at about 2500 RPM, and is somewhat intermittent.

Another issue that has been happening even longer is the on the dash, sometimes the seat belt light comes on for no apparent reason and the tack drops to 0 rpm for a minute or so. I think that is a problem with the wiring for the display, but am not 100% sure on that.

All regular maintenance has been done. Is there anything I should look at or try before bringing it into a shop?


The DB

When does the engine knock? While you are accelerating, decelerating, holding steady RPM ( cruise ). Does it knock when you let off the accelerator when cresting a hill?

 

[The DB]

When does the engine knock? While you are accelerating, decelerating, holding steady RPM ( cruise ). Does it knock when you let off the accelerator when cresting a hill?

I'm running premium fuel in it at the moment, which hides most of it. Currently with the premium fuel it knocks sometimes during acceleration and holding around 2500 rpm, and the automatic transmission seems to like that rev range.

I haven't ever heard it at idle, and haven't noticed it when letting up on the accelerator. I have noticed it happen when transitioning from a down-hill or flat area to an uphill, then it would stop after cresting the hill.

A while back I was using mid octane fuel to see if it would clear it up, it did for a bit, but in time even with mid grade fuel in it it would happen quite often. With mid and low octane fuel it happens much more over a much larger rev range.

I have noticed lately that it seems to happen more when the tack needle is at 0 (mentioned it above) but it is not limited to that.

I am thinking with the rate it is going that at some point it will happen more often with premium fuel as well.


The DB

 

[koda2000]

you say it "knocks" but from the rpm at which it does it (2500) it sounds more like the beginning of "timing chain death rattle". this happens on the SOHC V6 because the timing chain cassettes are poorly designed and break. this is a VERY common problem with this engine and is very expensive to repair (lots of labor). it sounds a lot like "ping" from pre-ignition, which is probably why you thought switching to premium fuel would help. my advice is just drive it as is. you may have many, many more miles before it gets really bad. my 4.0 SOHC has been rattling like a diesel truck for 50k now. next time you drain your oil, look for what appears to be grit in the bottom of the drain pan. it's actually bits of ground up plastic from your timing cassettes.

 

[2000StreetRod]

knock sensor

Your SOHC V6 has a knock sensor that can retard the normal ignition timing when knock is detected. With premium fuel and a functional knock sensor there should be no knock due to fuel detonation during cruise. Fuel detonation knock typically occurs when the engine is under moderate load in the lower rpm range and the throttle is depressed but not enough to trigger a downshift. This thread may help determine if you timing chain rattle: Timing chain rattle resolution process - SOHC V6

 

[deweyville65]

There is a major difference between "engine knock" and "engine ping". A proper description would greatly help diagnosis, especially from many miles away.

 

[Cranmaro99]

There is a major difference between "engine knock" and "engine ping". A proper description would greatly help diagnosis, especially from many miles away.

Yup. knocking = engine toast.