Hello everyone. My name is Jim and I'm new to the site.

I recently bought a 2010 Ranger with the 2.3 4cyl and automatic transmission. The truck has only 21,000 miles on it. 1 owner truck that the guy barely drove.

I have a question about a noise I'm hearing at idle. I'm hearing a rattle type noise, almost sounds like a diesel, clack clack clack. I only hear it at idle. If you rev the engine even a little bit it goes away. Cold start fast idle its silent. I literally only hear it at warm idle. My original thought was timing chain tensioners but I dont hear the noise in the front of the engine, I hear it more underneath in the rear. I was also under the impression you would hear it in other conditions other than idle if it was the tensioners. Am I wrong about that?

The noise seems to be coming from right around where the rear catalytic converter is. Could that be the culprit? Anyway to tell other than tapping it with a rubber mallet? The truck recently passes smog, so I assume its working ok. I'm not sure how California is doing smog tests these days though. I wasn't present at the time of the test.

Lastly, are these just noisy engines? My wife has a 2020 Explorer with the 2.3 EcoBoost and that damn thing is noisy as hell, so I know a little noise can be normal.

Other info, engine runs perfectly. Idle is smooth with just a slight vibration but its constant not like a miss fire. Engine pulls smoothly and feels like it has all its power.
Like I said only 21,000 miles so I assume its on its original plus and wires. I'll likely replace these since they're 11 years old. Any chance that could be the noise? I'm not convinced its that though as I hear it underneeth and the engine runs smoothly. I'll still do them though
The truck had a recent oil change at a Ford dealer. I assume with Motorcraft oil and filter. Levels all look good.

Anyway, sorry for the novel.
I'd appreciate any thoughts you may have.

 

Welcome to the forum...
Your Ranger is almost identical to the 2009 I got 2 years ago with only 22,000 miles on it, and with the same equipment. I did basically what your doing as far as tune up, but also did hoses and belts as it sat for 4 years.
As far as noise...the 4 cyl is a bit on the noisy side, and the lack of insulation and any type of serious sound deadening material doesn't help.
The noise you hear may be something as stupid simple as a loose nut/bolt/screw letting components touch at certain times. Check the exhaust system and heat shield...those are the easiest to check.
As far as your posting about surface rust on the rear frame, I had same problem, and mine was very minor. I just wire brushed the rust off and coated the area with Ospho, and gave the area a simple coat of non gloss paint...Rustoleum.
2 years now and still looks good. Your in a non rust belt area, so I wouldn't worry about it too much, but due to its condition you may want to "dress it up" a bit so everything looks new..

 

All 4cylinder engines suffer from "vibration" at lower RPMs, its because they only fire every 180deg of crank rotation, its why they are usually set to idle at 750-800rpm vs a 6cyl which fires every 120deg and can idle smooth at 600-650rpms

Rattle is most likely caused by the idle vibration inherent in all 4cylinders and something is loose, could be INSIDE a Cat but could be bolt/nut as well

Ford recommends the PCV Valve be changed every year on this model, but I think 2 years is fine, its a PITA to get to it, have to go thru drivers side wheel well
PCV Valves are "controlled vacuum leaks" so computer expects that "leak" and for it to change with engine RPMs and throttle positions, if valve sticks closed or sticks open it can cause all sorts of odd running issues and do it intermittently to boot, lol


2.3l Duratec does have an Aluminum head, so spark plugs should NOT BE over torqued as the steel spark plug threads can easily distort aluminum head threads
You should NOT remove or install spark plugs when aluminum heads are hot, I often read you should, do not do that
If spark plug seem overly tight to remove then someone goofed when installing them, over torqued them

You can easily cross thread aluminum heads, so install spark plug by hand, if it seems tight STOP

Between spark plugs 3 and 4 there is a sensor, CHT(cylinder head temp) sensor, this replaced the ECT(engine coolant temp) sensor used in other engines
While not a common failure it is a known to fail sensor, it will set a code, and temp gauge on dash will not read correctly

 

Great info thanks.

I'll add a PCV valve to my list.

I'll poke around under it next weekend and see what I find. I'm less concerned about it today than I was last night. We drove it around all day and it ran like a champ. You can only hear the noise when you're next to a building, like in a drive through or standing right on top of the truck. Otherwise it sounds normal. Like Grumpaw said above, these trucks dont have the insulation modern trucks have, so you hear everything.

I'm familiar with dealing with aluminum heads, but thank you for the warning. Its not fun when that goes wrong. Any thoughts on anti seize for the plugs? I've heard you should absolutely use it and in other cars with aluminum heads they say no way! Whats the consensus for the Duratec?

 

Had a motorcycle mechanic tell me years ago that he always put a dab of nickel anti seize on any plug he was installing in an aluminum head. Since then I have always put a pill sized dab on any plug I've installed.
And he told me to use nickel based anti seize which is apparently a bit different from the normal stuff. That and just a very small amount....problem is that many use way too much when applying it.
Still do it to this day, but that's just me...