2.5L Knocking DIAG

[White_Comanche]

Somewhat recently I began noticing a knocking sound on cold starts (during cold months). After warmup, the sound always has subsided.

 

I used this excuse to buy a compression test kit and stethoscope. The plugs are semi-new 3yo NGKs. Cruiser54 suggested them. Guess by now some condition of the engine is now present.

 

KNOCKING SOUND: Upon startup, the sound/vibration is a strong "knock-knock-knock" and after a little warming it drops down to just a "tick-tick-tick". Probe of this tool pinpoints the general area the sound is loudest (top half/front of engine).

 

BELOW: those are snaps of my current plugs along with their compression test results. Numbers may be not be totally accurate... it took much too long taking plug #1 out. So the engine was fairly cold when finally testing.

 

 

 

 

 

 

 

 

 

 

 

 

[eaglescout526]

1 looks like it’s not getting enough fuel

2 looks rich

3 looks just right

4 looks like it’s not even putting in any work. 

[89 MJ]

Compression is fairly even, that’s a good sign. Numbers seem a little low, but these weren’t a high compression engine from the factory and none seem too low to run. 
 

I agree with the spark plug assessment. 
 

Ticking sound could be an exhaust leak or something with the valvetrain. 

[White_Comanche]

Greatly appreciate the insight. You guys must know how to read the subtle differences in plugs quite well.

 

It's somewhat reassuring to know the 2.5L was not a high compression engine. Yes, I agree my results seem a bit low, however.

 

Ultimately this would be a project for way down the road... or even fit for my mechanic. The engine itself runs quite well. Don't think it lags in performance much either. Of course, I don't have a rebuilt 2.5L to compare it to. Will look into the noise further to narrow it down to valvetrain or exhaust leak.

 

IN SUMMARY, the knocking sound is audible at startup on cold days / cold starts. After warmup, the knocking sound calms down... and the only way to hear the tick-tick-ticks is to use a stethoscope.

 

What I'm gonna do later this year is buy a new set of plugs. And after sometime I'll pull them, do another compression test, and document how they look again. My current plugs were removed initially about 1 year ago and I may have got them mixed up between cylinders. Plus, they received the torment of a terribly running engine as I was sorting out the issues one at a time.

[Ωhm]

Spark plugs are one part of the secondary ignition system. Replace cap, rotor and wires. All are maintenance items.

[White_Comanche]

When I first got on board on CC, Cruser54 had me replace the cap, rotor, wires and plugs. The truck ran much better after, but more work got done since then to improve engine performance and startup reliability.

 

Now it runs pretty well after those projects got tackled. 

 

I've not inspected my new cap and rotor since installing. Wires all look fine.

[eaglescout526]

41 minutes ago, White_Comanche said:

Greatly appreciate the insight. You guys must know how to read the subtle differences in plugs quite well.

You get good after a while haha. Knowing what normal condition plugs should look like, everything else will look odd or out of place. White with brown is too lean. Darker than brown is rich. Anything else is a sign of another issue. Like for me on the eagle, I found cyl 5 to be a problem. Coated in all sorts of carbon build up like this:

 

I knew something was wrong right away. Initially didn’t think head gasket but this ended up leading me to such. 
 

But as stated, it’s not a high compression engine, your numbers look great and healthy, it’ll keep chugging along. Though cyl 4 has me a bit on the intrigued side as to why it looks like that but as long as it doesn’t feel like it’s missing a beat when running, keep on going!