My late 99 has 161K, I am the 2nd owner and bought from the Original owner. It is stock with no tunes. Auto/4wd.

It has had an intermittent idle knock and recently has gotten much louder recently when used heavily with towing for summer camping in the 7K range up steep hills. The knocking goes away above 12-1500 rpm. There is no noise when the engine is cold. It seems heavily temp/load/heavy use dependent. If driven lightly, the knock is quieter but still present. The trans was recently rebuilt and new billet converter installed, made no difference so it's not that it would appear.

I rec'd blackstone last week and the results are excellent.

Running the cyl contribution test while hot in drive at idle reveals cyl 8 is running 4.9 to 5.4 Perdels. #3 is 2.2 to 2.8. 1,6,7 are 0. 2 is .6 and 5 is .4.

I haven't checked bolt torque yet. My question: Is #8 "fixable" potentially with bolt torque? Is it considered too far gone and should just be replaced?

Thoughts?

 

5% perdels on #8 is high-ish but not "bad". Kinda like oil consumption of a quart per 1k miles is not good but considered normal. Re-torqueing the injector bolts might help. My first thought is fuel pressure falling off under load, dying fuel pump or dirty filter. A new fuel filter would be my first step, then monitor fuel pressure under load. Need a fuel pressure gauge for that tho.

 

The fuel filter was replaced 4k miles ago with a Wix all-in-one deal. I do have a new cap and separate filter available to install. I did the hutch/harpoon about 3k miles ago.

I also have a box o parts waiting for time to install that includes a cncfabrication 4 feed line kit, new poppet kit, and gold spring. The 4 line kit has an easy fuel port to run a gauge on albeit, with the hood open.

In short, it sounds like the suggestion is to change the fuel filter, check injector bolt torque, and see what that does?

Screenshot of a datalog:

 

PERDELs can be misleading, specifically with #3 and #8. Do you feel a big miss? You would with a PERDEL that high.

I would get a new CPS (like the one Riffraff has), swap it out, and take your Cylinder Rotational Velocity readings again. I'd bet you get completely different numbers. Don't get rid of the old CPS, because if nothing else - everybody really should carry a spare CPS.

A knocking injector is hard to isolate because of all the other engine noise. I've used everything from a paper towel tube put to my ear, to a mechanic's stethoscope, to a long screwdriver touching the engine and my temple. The offending injector can be isolated by ear - it's just not easy.

If you can trust that the problem can be reliably duplicated, popping the valve covers and running the engine in the driveway will allow you to check the torque, hear the injectors directly, and observe the oil flow from the spouts. I have done this countless times.

 

Based on some of the reading prior, I did install the RiffRaff CPS so, that is captured in these readings. The noise is very repeatable--daily. The knocking just gets obnoxious after having a good pull. The engine seems to run smooth with no misses. No smoke on cold start or driving either by the way.

Looking for best course of action. Injector replacement is fine if necessary but would certainly like to avoid if it's an "easy" fix....

 

Torquing the sticks cleaned up a lot of knocks in "Stinky". It's free, but it's a bit of work if you haven't had practice at it. 120 INCH pounds for the injector bolts.

For fun... set the wrench at 50 first. If the bolt turns, you need new O-rings on that stick. I know from experience that 75 inch/lbs will knock (and leak ICP).

 

Sounds good. I'll go through the following since they're either due or I have the parts already:

• Oil change and new filter including archoil
• Install billet fuel press. housing with new poppet kit and gold spring
• Torque all injectors starting with 50in/lbs final to 120in/lbs
• check electrical connections
• 50 cent mod
• run engine with VC's off to confirm if #8 is the one knocking but hopefully not after the prior items are completed.

I've removed the HPOP lines and glow plugs...decided those may interfere with the objective of diagnosing #8 idle knock...

If this doesn't fix the issue, I'll have to consider buying a new injector for #8 I suppose...

 

+ injector orings?

 

I'm not so sure O-rings will go straight at injector knock. The one thing I know for sure is a rolled cushion ring (top squared O-ring) will lead to loosening the injector bolt, which leads to knocking and other woes.

 

I was thinking along the lines of HPOP pressure bleeding off through worn orings.

If either the fuel or the oil pressure builds up in the injector to a point, then bypasses an o-ring in part, wouldn't that lead to erratic pressure in that injector, which would affect the fuel delivery when it goes to fire, causing a knock?

I'm asking, not telling here

BUT-

1. That is just my thoughts based on looking at the design of the injectors. I'm still learning

2. I haven't changed injector o-rings yet. Maybe this afternoon? After that, I may be quick to recommend how easy it is to change them, or recommend one avoids touching them unless absolutely unavoidable- depending how it goes

3. I am taking your caution against rolled o-rings quite serious. Plan to "practice" with driver's side, removing airbox and whatever, using one with the most access.

Remember, I had a similar PERDEL problem on #8, before changing CPS (old was light gray) and changing oil from Delo 10w-30w partial syn (due for change) to Rotella 15w-40w Dino.

I should run a CCT today before starting the other work to see if that helped.

I'll post all that in my build thread, too, but figured since the OP is heading down some of the same road, he may benefit from the discussion and info

OP- I said the exact words about replacing injector(s). If necessary, but not blindly throwing $$ at it

Have you logged a WOT run for Tugly to analyze yet? He and some others have a real "Eagle Eye" that often finds readings out of line under stress. It's a HUGE service they do to help others. I whole-heartedly recommend you take advantage of it.

When you do your run, log a few mins before and after the run, trying to get the knock in the log, too.

With the new software they're using, the longer log files aren't really a problem, with analysis of multiple sections being quite simple.

Case in point. They found a disconnected EBP sensor (after I rebuilt my fuel bowl and forgot it), and a biased ICP sensor because the old oil from the failed sensor had drained down the harness into the new sensor's connector due to lack of proper cleaning on my part when installing the new sensor.

All this, and my truck was running GREAT! It was my best run, smooth, strong etc. But the numbers don't lie.

I figure since you have PERDELS, you have the equipment to run a log, no problem?

 

My naive thought on this is that other than the erratic idle knock that is sometime flat out obnoxious there are no other "bad" symptoms. Engine starts easy and reliably, no smoking whatsoever even when dead cold. I figure if I had an O ring issue, I would have another symptom?

 

I'm kind of thinking that if the action items I have listed (revised list) do not address, I will just buy a new alliant AE injector. I'm not in the mood nor have the luxury of time (busy camping schedule this summer) to mess around with this too much.

Further, if the only symptom is still just the idle knock after completion of the action items, I may just leave it. At least I will have taken steps to remedy and in theory improved the truck a bit more. Then I'd still plan on buying an injector and replacing at a later time.


ExPACamper, yes, I do have auto enginuity. Still learning it but it's pretty easy to setup from what I can see so far. The knock is only at idle. goes away with ~12-1300 rpm. Additionally, it is only present after certain conditions. Some are still unknown with easy daily driving, but consistently will knock after a hard pull with the trailer or longer drive. Not sure a WOT pull datalog would do much. If there are other data elements to log aside from PERDELS and oil temp, I would like to know.

Yes, I TRULY appreciate the assistance here! I'm quite saavy with mechanical work on hot rods and such and am very well tooled up but, the 7.3 is a new world for me and I just don't have the background knowledge yet.

 

As an example, a WOT can tell you if your hpop to opt to icp ratios are correct or if something isn't keeping up.

Lower rpm can be affected by this.

Many more items, better explained by those with more experience LOL

 

Valid point. Well, this weekend I'll complete the to do list and see what happens. Hopefully something as simple as the new filter and torquing the injector bolts solves it. It CAN happen that way sometimes. I'll inspect the IPR tin nut and icp connector for leaks while there JIC...not that these are suspect with the knock.

 

[QUOTE=SRBF150;15395893]I'm kind of thinking that if the action items I have listed (revised list) do not address, I will just buy a new alliant AE injector. I'm not in the mood nor have the luxury of time (busy camping schedule this summer) to mess around with this too much.


Look at it this way....Just think how bad your moods gonna be if you don't take the time to track this down and it turns out to be a Rod a knockin.....Not to mention your camping....Half way to Cali..towing a mile long Fiver..... up the Grapevine....As Camper says, Don't ask me how I know...


Ever Swap out an injector, On I5, in the dark?