Knocking, pinging, or just normal?

[sparkyputerguy]

Hi gang!
My '00 XLT 4.0 OHV has been great so far- 22K miles and will hopefully keep me trucking for quite some time.

The question (Part 1)is this- In the mornings when I start her up, I hear the knocking sounds coming from down low (sounds louder when listening under the truck rather as opposed to listening topside with the hood open). The noise goes away after a while. Is this probably the carbon buildup thing?

Part 2- it sounds smooth under normal acceleration/cruising, but there's a noise that sounds "not quite right" under heavier acceleration. This is either acceleration from a stop or chugging up a hill. It's a light knocking (which the manual says is normal) but it doesn't really sound like metal-on-metal. It's more of a sound like someone gargling with mouthwash. Is this normal? Could it be an exhaust leak, or a vacuum leak? I've checked all the hoses and they seem tight- and there's nobody filming a Listerine commercial either... I mentioned it at my last service appointment but they didn't hear anything out of the ordinary. I use regular gas, usually Exxon or Mobil. Cleaned the MAF sensor the other week and disconnected the battery to reset the 'puter.

I guess I can always crank up the stereo...hehehe.... Any ideas?

 

[TarHeel085]

wait a sec, you have the ohv in a 00 XLT? its cylinder knock, (i think) my sohc does it, just next time you fille er up put in premium.

 

[Jason_25]

Originally posted by TarHeel085
wait a sec, you have the ohv in a 00 XLT? its cylinder knock, (i think) my sohc does it, just next time you fille er up put in premium.

He said OHC- as in overhead cam

By the way, IMO engine knock is unacceptable in a newer vehicle such as that. There is no reason why you should have to run premium gas in a truck designed for 87.

 

[sparkyputerguy]

Sorry- my crackheaded mistake. I have the OHV engine. I tried to edit the message but every time I come back, it still shows the OHC. (A little too much caffeine today....)

 

[TarHeel085]

my car knocks, my friends 99 Grand Cherokee does it, my friends 95 blazer does it. youre supposed to put premium in it somethin like every 5 times, just to keep it clean. its just normal, all domestics are gonna do it.

 

[sparkyputerguy]

There's got to be a knock-knock joke that shows up here...

 

[Jason_25]

hah i understand.

I don't "think" I have the noise that you are describing in the upper RPM area, but I very rarely rev it beyond 4000 RPM's, mainly because I don't need to, it's quick enough for me. I would rule out vacuum leak, It would be more of a whistle I think. At exactly what RPM does this begn to happen?

As for your idle situation, I can relate. It's the phenomenon known as piston slap. From what I am told, it is harmless. Doesn't really bother me that much. Go listen to a jeep cherokee with the 4.0 I6, then you'll REALLY know what piston slap is.

 

[TarHeel085]

thats exactly what my friends does, its VERY noticible, unlike mine, just gets annoying.

 

[sparkyputerguy]

Yep- the engine's always quieter on the other side... or something like that. Maybe the grass is greener... I dunno.

The knocking usually happens between 2500-3000. I rarely take it past 3000.

My wife has a new 4-Runner and it's so darn quiet! I got a speeding ticket the other month doing 74 in a 55 while driving it and talking about our wedding plans. Had I been in the X, the noise would have indicated that I was going too fast and they wouldn't have clocked me going so fast... or maybe they would have!

 

[Jason_25]

"All Domestics are gonna do it"

That's not actually true. My mom's 5.0 Explorer has never made any sound out of the ordinary. I have also never heard of running premium once out of every five times. Running premium gas would actually cause even more carbon buildup in the cylinders because it would leave unburned fuel in the cylinder.

Tarheel, I beleive your truck does it because of all those problems the SOHC has. Most notably, the timing chain tensioner and then that other thing (which I cannot remember off-hand).