Piston Slap: Gently Tapping, Tapping at My Ranger's Door?

Sajeev Mehta
by Sajeev Mehta
piston slap gently tapping tapping at my rangers door

Dave writes:

Hi Sajeev,

This is the second question I’ve asked on here, and while I didn’t even follow the advice I received last time and here I am again! Last time I was asking about a sporty car, and I ended up getting a 2007 Ford Ranger, 2.3L, 5 speed, with all of 35,000 miles on it. It is a regular cab with nothing extra on it, a real throw back, manual windows, no AC, a nice basic truck with nothing to go wrong right?


In the past two years we’ve put maybe 5,000 miles on it. It’s our second vehicle and it sits a lot except for weekends going to the to the dump, hauling kayaks, bikes, mulch, etc. Just what it was made for. In that time it has developed a serious engine knock (maybe even piston slap?). It runs fine otherwise, especially with a load and at low RPM when empty. Fuel mileage is fine, nothing in the oil except oil, doesn’t use fluids, just makes a god awful knock, especially when shifting. I first thought of detonation, but at low revs with a load in it nothing. I took it to a local shop I trust to see if they could find out what it was. The best they could come up with was it was in the #4 cylinder, they disconnected the spark lead and the knocking went away.

They suspect a wrist pin or main bearing. I suggested dropping the pan and switching the #4 piston, connecting rod and crank bearing out and maybe miking the bearing journal to see if that needs repair. They looked at me like I was nuts. Am I? Seems no one does engine repair any more, are they all throwaways now? They suggested a used or rebuilt engine and a cost of 3-4500$ for the whole job. I wonder if the truck is worth that much, but I can’t really sell it the way it is and it is useful around the house.

Any suggestions?

Sajeev answers:

Well hell…considering my daily driver is a fully optioned (i.e. carpet, A/C and power windows) version of your ride, this has me more than a little concerned. And then this YouTube video.

From what I Google, some Duratec Rangers have a problem with rod knock as they age. Or maybe it’s a timing chain issue, like the YouTube clip above. It might stem from neglect and over loading the truck. Who knows, especially considering the Duratec Ranger’s crank is beefier than an ordinary Duratec I-4 unit.

And while you can easily (so to speak) fix the offending spinny-part with basic knowledge of what parts comprise the Duratec family of engines, the truth is these are throwaway motors to most folks. And most mechanics. And that’s probably the way it should be.

My advice? You can try one of the magic oil additives, I once used Lucas to hush-up a growly crank on a 5.0L V8. But without a doubt, drive it until the motor pukes: don’t spend another dime trying to diagnose this. Then worry about getting a “new” throwaway motor.

Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.

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3 of 46 comments
  • Nrd515 Nrd515 on Sep 06, 2013

    A guy I went to school with had some old battlecruiser, a Buick 225, I think, and it made a horrible noise once it got hot. This was auto mechanics school, so we yanked the pan and the bad rod bearing was pretty easy to find, it was on the front crank throw. We pulled the cap on the rod that looked slightly "cooked" and the bearing was trashed. The crank looked all right. The teacher got his caliper and micrometer out, measured everything, went to a parts store, came back with some crocus cloth, plastiguage, two sets of rod bearings, and a can of STP. He cleaned the crank up with the crocus cloth, washed it with some carb cleaner, put the first set of bearings on, with the plastiguage, took it apart, looked at the little thread, and said, "looks good", put some STP on the bearing shells, and put it back together. The rest of the STP went in with an oil change on it, "just to make sure the first couple of minutes it runs doesn't do something bad". It sounded great, and 5 years later, it was still running fine with nothing more than a water pump change out. I would give it a shot.

  • Trk2 Trk2 on Sep 06, 2013

    Check the swirl flaps in your intake manifold (similar to throttle body flappers). The shaft that supports the flaps can wear (and will typically wear at the #1 or #4 cylinder) which causes the flaps to tap against the intake manifold under certain conditions. Search for Duratec swirl flap (also called swirl plates or tumble flaps).

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