91 4.0 OHV Explorer has random light tap under light load in gear | Ford Explorer Forums - Serious Explorations

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91 4.0 OHV Explorer has random light tap under light load in gear


Active Member
October 25, 1999
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My 1991, 4.0 OHV, Explorer has a random light tap between 800 - 1,100 RPMs, under light load in drive or reverse. Seems to be most noticeable when the engine is warm - hot. First noticed at an ATM drive-thru, as I sat in drive at idle. I can't seem to isolate the sound. In park it is not detectable.

Auto transmission rebuilt 7K miles ago. Made sound before and after. In addition, the bottom of my engine is constantly wet with oil. Looks like the oil filter adapter at the engine may be leaking. Ever seen this?

Looking for any feedback.

Thank you,


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What is a light tap? I have never heard of anything described this way.

Are you meaning spark knock? Or a tapping noise comming from the engine area?

The tap is more of a "thum thum thum thum thum" sound and is constant only when the engine is in gear (under load) at 850 - 1,100 RPMs or so. In neutral, it appears to be gone. Noticed more when going up a hill or "power braking" at 850 - 1,100 RPMs. Can't be heard from inside vehicle, unless windows are down and next to an item to reflect the sound into the window.

I feel confidant that it is not the heat shields. I believe that the sound is coming from the passenger side front area of the compartment.

I guess I need to do the old long extension to the ear test, to isolate more.


Have someone sit in the vehicle and hold the brake and rev the engine up untill you hear the noise then try to figure out where it is comming from. 800-1500 is not alot of rpms for the average person to hold the brake pedel down and not be able to hold the vehicle still. Could set the ebrake too, just to be safe. But I wouldn't do it for long periods of time might mess something up????

mine does that to but only in drive or reverse then myine makes like lifter noice when cold then when it warms up it makes this noise like you discribed when at a stop light or in drive tru i can kinda fell somthing it the floor that folows it and i have no clue what it is eather

Ive got something similar