Knocking and smoking

About 3 weeks after an oil change, my 01 Ford Ranger started knocking and smoking when I accelerated up hills. I checked the oil levels to find that it was completely empty. Refilled the oil, but the problem persisted. Tried gas additive–nothing. Finally limped into the Ford dealership where they kept my car for 6 weeks trying to figure out what the problem was. After new plugs, wires, MAF sensor, coil, and PCM the problem seemed to be fixed…mostly. Knocking and smoking eventually stopped until I checked the oil levels again and it was empty. Added oil which started the symptoms all over again. Mechanic ruled out blown gasket. Claims knocking and smoking are unrelated (even though they happen at the same time 100% of the time). Smoke is white. Knocking (at its worst) sounds like a bolt rattling around in engine. Car does not lose power, and when I gun the engine it seems to go away. Only happens going up hills (of which Tennessee has plenty of). Suggestions?

Sounds like serious mechanical damage was done by running with very little oil.

Did they do a compression test in those 6 weeks?
Any signs of oil leaks?

I think it’s time for used or re-manufactured engine.

In the future when you get any work done on your car check for any obvious mistakes before you drive away.
Even after a simple oil change. Open the hood, check the filler cap, start the motor, look underneath for drips…
When a car is suspected of oil loss check the oil more often, like every fillup.

A few basic tests such as a compression check and oil pressure test should tell someone all they need to know and that should have been their first step.
Running the oil down to nothing once, much less doing it twice, will ruin the engine in seconds.

The knocking could be due to damaged rod bearings or possibly an EGR fault; or both. A bearing knock can become worse when the load on the engine is increased and a non-operating EGR system can cause a spark knock which is usually prevalent when the engine is under a load.
A spark knock can be made worse by excessive oil being admitted into the combustion chambers and that goes back to the damaged engine scenario and compression test.

Wow; 6 weeks and these guys can’t get a handle on this while shotgunning a crate of parts at it?

This sounds a lot like collapsed hydraulic lifters. The clattering is distinct. You have a major oil leak causing oil pressure loss. Without enough pressure the lifters have serious problems this can include a cylinder just pumping out raw gas in a white cloud. The dealer seems to have missed the mark and should be held liable for a simple failure on the diagnostics This is classic and should have been in the high school tech class.

Please define “Completely Empty”… How many quarts did it take to read “Full” on the dipstick?

I have a 1998 Ford Exposition 5.4. I got it from a cash car lot Friday… From Friday until Wednesday it was fine… Wednesday night it started this loud knocking and rattling sound under the hood… And smoking too!!!.. Some say it’s a gasket leak some says new coil pack or wires or ignition coil or cylinder…i think its an internal oil leak please help!!!

Katrina, welcome to the car talk community. You need to use the dipstick on your engine and immediately check the oil level. If it is below the “add” line, add oil a quart at a time until it is at the “full” level. Do not drive the car any further until you do this.