More Knocking....Im seeing a trend here...

[Crash]

Hey,

I have a 98 2.5 2WD 5 speed with 202 000kms. Running 10w-40 semi-synth

Here's the situation:

When in high gear [4th and 5th, but sometimes third] whenever I tromp on the gas, or try and accelerate uphill / under load, it makes a decided knocking sound. Now, I know what you're thinking, and it's not the sound that I associate with a fuel / timing problem - I think those sound more like a popping noise anyways. Its a fair bit louder, and sounds more like a vibration ... like something is rattling, but loudly and regularly, and ceases instantly when I back off the gas, even the slightest amount. If pressed, i would describe it as a metallic tak-tak-tak-tak-tak sound [....how many of you just made that sound out loud?]

I have been thinking the knock was bottom end, bearing issues - i tend to think worst case scenarios, and it would make sense as the stress on the engine is most severe under load in the more direct ratios. But lately i've been thinking that it doesn't sound like bearing knock either ... too light a sound [and the truck is still running....]

So im back to the drawing board... motor mounts? transmission? valves [only in high gear?]


I'm kind of stumped, so I'm deferring to you fine gents....

 

[Joe400]

Are you sure its not pinging? as you probably know, that occurs under heavy acceleration or when the engine is under more stress than usual. Pull some spark plugs and see if they look normal. if the insulator is chipped, or the electrode is pitted, its probably detonation. also.. why are you running 10w40?

 

[zamos]

What grade gasoline are you burning - Try a tank full of premium and if it still makes the sound then look elsewhere

 

[Crash]

yeah, I've pulled the plugs all around and they look fine [great in fact]. Wires are relatively new.

Running 10w40 to quiet things down some - theres a bit of valve noise, and as I mentioned before, i thought bottom end bearings may be suspect, so I ran a heavier weight to see if it would quiet em down.

In my previous 90 2.9 ranger, the lifter noise was absurdly loud - a heavier weight oil with a bit of detergent made them nearly silent, so I thought I would give it a shot in this one.

 

[Crash]

tried a couple of tanks of premium, with injector cleaners, and a few with octane boosters, still there...

 

[Jspafford]

What RPM's are you running when you tromp it? If the engine is below it's powerband it may be a normal 'lugging' sound.

How are your universal joints?

Or are you sure it's coming from the motor area?

 

[Ranger44]

Knocking....Jspafford those could be it. Maybe a clogged PCV Valve. Those cause a knock at times. Just shootin into the dark.

 

[Crash]

Thanks for the advice - I'll replace the PCV valve and look at the driveshaft...

The exact source of the sound is hard to pin down, but definitely forward of the cab.

Would the u-joints complain at the lower gears as well? Are they greasable [I think they're called zircs in the lower 48]? For that matter, is ANYTHING greasable on these rigs?