Octane rattle so Im told…

[Blackwater]

1999 5.4 with around 170,000. Motor is strong. No other issues.

I was told it was a octane rattle and I should run a higher grade gas.

It can happen ramdomly but more so when pulling a a small trailer. The rattle sounds kind of like a loose shield on the manifold or cat. The noise can come a go day to day. This rattle is only right before it shifts gears or a steep or long incline.

Has anyone had this and or knows what it might be?
I really don’t think its lifters, valves or anything like that.

Ideas?

 

[98EXPY 5-0]

Sounds like its pinging. My Dodge does that with 87 octane gas. Sounds kinda like the ball in a can of spray paint. The guy I bought it from (who bought it new) put 93 in it from day 1 and now if I don't do the same it pings.

 

[JUST4FUN]

for this both of you need to take the EGR off and clean it and all passages
into the intake the EGR has a cooling efect on the combustion chamber
cloged passages cause pinging

 

[Blackwater]

Just4fun, Thanks and I will take a look at that first thing in the morning. Have you heard this before and seen a good result after doing a clean up on the EGR?

98expy , Thats the sound alright! But it pinging/rattle got worse.

Im going to make another thread about oil loss. Do you think oil would have anything to do with it?

 

[davesexplorer]

Octane rattle makes me think of detonation which I think you would know if you had that problem. If it sounds like a loose metal kind of rattle - possibly your timing chain and/or tensioners worst case scenario?

 

[Blackwater]

Spark knock....I couldnt think of the term or name before. Turns out the pass side PCV hoses " 3, 90* hoses had some rather large holes on the inside of the bend.
No more Spark knock and that might be the missing clue to oil loss too. I guess Ill know soon enough!

 

[98EXPY 5-0]

I would think that if you were losing oil from that hole, the whole side of your motor would be covered in oil vapor. I can't imagine a hole there being a good thing, but I'm not sure it can account for major oil loss. Especially without being obvious.

 

[Blackwater]

I hear ya! I didn’t think I could have that kind of oil loss either. I looked in a Hayes book to trouble shoot and oil loss and or consumption has PCV listed. So I checked it out. I fixed it and haven’t seen a loss yet. I could have just made a mistake with the oil too….Yup I wouldn’t put that one pass me!
Dude also I have yet to see another 5.4 with so many hoses on the left rear side of the motor on any other trucks. Its like a rats nest! I put stock new elbows/tubes on the other day. I didn’t have a spark knock but it started again today. I checked it again and with all the other hoses piled around it kinked the elbows. I went and added heavier hoses replacing the elbows and extending the lengths to move the junctions out of the way. Did a test drive and I no longer have any spark knock once again! lol