Can I solve early engine rod knock?

I’ve been noticing that my 1994 Ford Ranger 2.3L, 4 banger has a slight knocking sound. It is really faint compared to any other rod knock I have heard. An engine compression test shows mid 140’s on all cylinders except one of them which is at 125. I’m guessing it isn’t receiving enough oil. Can I prevent catastrophe by fixing this early on before a rebuild or replacement has to happen?

If you have as many miles on the engine as you say you have… I won’t even be tempted to guess. I sell any car with a 2.3 Ford engine, like the one in a 94 when it gets to 140,000 miles. If it is in a car I try for $400 or junk it. It’s in a pickup so the situation is slightly different and not as routine as junking it by default.

Yep looking for solutions to fix it. Any suggestions on how to fix it?..

Given those compression numbers & some knocking, I’d say that your best fix is to just go for an all out rebuild. I doubt that any partial fix is going to be worth the trouble.

Of course, it also depends on long term plans. I have an Escort with a 2.0 that’s had a light knock for the last 80K miles or so. I just keep driving it. Its got better compression numbers than that too though.

Are you sure it is not a valve tick from a collapsed lifter? A valve tick will sound a lot less deep than a rod knock. Of course, a true rod knock will get worse quickly as the crank and rod will quickly deteriorate. How long has it been doing this?

Could it also be piston slap and not rod knock? Especially your Escort, cigroller. I cannot imagine a crankshaft and rod knocking for 80K without blowing apart. Are they made of Adamantium or Unobtainium?

BK, I actually have no idea what my knock is - its low end & its been there forever. I don’t think its piston slap as I have that in my GM 3.4L & its nothing like it, although I would be more likely to describe it as a slap rather than a knock so my guess is that it might have something to do with some piston slop at least. Its low end & not all that loud. I asked a guy a my shop once. He just shrugged & said its an Escort - they make noise. I don’t really care too much. Every mile this thing is on the road saves me money.

But as for the OP - the last time I checked compression I was 172-180psi across. This Ranger is around 140 with one cylinder at 125. That’s not an engine worth minor repair IMHO.

The rod bearings are about the last thing to starve for oil if you have low oil pressure. The valve train will suffer first, though worn rod and main bearings will CAUSE low oil pressure. It’s probably just normal wear at this point. It could keep making this noise for years with no intervention, or you could try a little higher grade of oil to see if that quiets it any. Eg. go to 10W30 from 5W30. If it isn’t too bad and the pan is accessible, you could try throwing another set of bearings in it. If you’re barely hearing the noise, the crank is likely fine. Since you also have a cylinder that is a little weak, you might go for a full rebuild or different engine if it gets too bad, assuming it’s worth keeping the truck.

Actually, oblivion, 5W-30 and 10W-30 will behave the same at operating temps. He would need to go to 10W-40 to get the benefits of a thicker oil at operating temps.

+1 to BK… As others have said, with the comprssion being what it is… Your kind of on borrowed time as it is. Can you try this, with the motor running remove the oil cap… Any change in rpm?? if you put you hand over the oil fill hole do you feel air coming out??

Let us know !

Those engines are well known for piston slap…not detrimental or longevity shortening…unless caused by melted piston(s) from preignition. I’ve seen this many times too on the 2300.

10W40 would be fine too. I guess my point is that the base stock of the oil is a little thicker and would provide a little more overall protection.

I would just pour a quart of Lucas ON TOP of the oil already in the engine…or drop a HALF qt and then add a QT of Lucas…or 90/140W Gear oil and run her 1/2-1 Qt overfull… Aside from a rebuild there is little to be done… Like Cigroller said…you could run 50K+ like that w no probs… Of course no extreme duty stuff with the truck… and it may last a very long time. The Lucas may rid you of the noise all together with its Oil thickening/over clearance space filling/cushioning properties…

The permanent solution is a rebuild, nothing less. But you may find Lucas works quite well… Maybe go up in viscosity on the oil in your crank case as well. If you are running 10W/30 say…go to 10/40…or 20/50 (warm climates only please) AND THEN do the Lucas.


The compression is way too low because both 140 and 125 PSI sucks. Run a wet compression test and you will probably see those numbers climb. This means piston ring problems.
Sounds like the engine is prematurely worn out to me.

And when the time comes I’d swap in a rebuilt engine, not rebuild that one, unless you know a great rebuilder.

Detonation…ping ping ping…the rear 2 cylinders of the 2300 are prone to piston crown melt and subsequent skirt galling …usually that’s all. Nothing a sleeve or a new block or something wouldn’t fix…unless you’re lucky and the cylinder walls are usable…not usually the case.

Wow that was a great set of suggestions. My mechanic said that between 101to 160 psi is well within reason. If it were brand new it would be in the 170’s but I am at 190k miles without a rebuild. There are absolutely no oil leaks, did a wet test and and it passed.

What I’m hoping for are easy solutions or preventative measures to prolong the life of the engine such as replacing any easily accessible gaskets or seals without yanking the whole engine. Maybe replacing the seals around the manifold…? Any recommendations? Are the lifters accessible without pulling the engine?

GSRagtop I’ll give your method a try and see if I feel air coming out of the oil fill hole. It is such a slight sound that almost know one notices it as being abnormal, but I can hear something is off, although it did not make the sound today. As I start the car there is a slight pulsing as if it would one day get more drastic and just die if I don’t fix it now.

Here it sounds like this guys but much less noticeable:

Short of what’s been mentioned I can’t think of anything simple to fix/slow the problem.

Definitely not a rod. I think BustedKnuckles nailed it in his first post when he suggested a lifter problem.

Engine noises can be difficult to differentiate through PC speakers but it does sound like a valve lifter.

However, your engine has problems in spite of what your mechanic may say and for several reasons.
He says 170 when new and the current readings are normal. No they’re not normal. Those readings are signs of a worn engine and there is too much variation between cylinders. (125 to 140)

The rule of thumb on compression is 20 X the compression ratio. The CR is 9:1 so do the math and you have 180. If an engine is well maintained, not abused, not overheated, etc, etc. then it should still be carrying good compression at 190k miles. Jeez, my old Mercury was still carrying 160 at 400 k miles and both of my last 2 Lincolns still carry 190 at around 200k miles and 250k miles, respectively.

You say it “passed the wet test”. What does that mean?
If the readings went up then the rings are worn out. If the readings stayed about where they were during the dry test then you have a cylinder head valve seating problem. Pick your poison.

Maybe the mechanic has been getting his info from a Chiltons manual and every Chiltons I have has the same bogus informantion in it.