With my wife's 2005 Ford Explorer 4.0 6 cylinder with 157,000 mi. The mechanic advised the timing chain had stretched and it's causing a ticking... a 2300$ fix because apparently the chain is on the backside of this engine and the engine has to be pulled to access it. I can't afford that right now. The mechanic added some Lucas oil additive and the ticking went away but now while traveling down the road at about 45 mph cruising feels like it we hit a pothole in the road even though there are none. It did not do this before Lucas oil additive. Changed coil pack, plugs and wires wondering what else could be the issue and can a timing chain slip. Also... it only happens once in a 30 min ride. There is nothing I can do to make it happen. No sputtering or starving for gas. Just a split second bump. Also the fuel filter was changed in a cheap effort to fix. The transmission has never given us a problem. No rough shifts. I don't think it's that but I have never experienced this.

 

The bad thing is after you fix the timing chain, up to about 50,000 mile later the trani might go