Aside from octane issues, what causes noise under heavy load?
 

Yeah, aside from octane issues, what causes intermittent rattles (definitely coming from the engine) under heavy load? Weakend valve springs? Happens sometimes when I punch it hard in 4th...

Any ideas? Thanks! :D

too much timing and or knock sensor not working right

Mustangs dont' have knock sensors.

Sounds like detonation to me.

Can we get a little more info? What kinda of car? mods? what is your timing set at? what octane fuel?

-Josh, aka the tireburner

No knock sensors?
 

No knock sensors in the 5.0's? New to me. I do agree with the detonation diagnosis though. Too much advance is my guess.

Rev

Re: No knock sensors?
 

I'm not 100% on the new ones but I know for a fact that fox bodies don't have a knock sensor

5.0's?
 

Pretty sure that the efi computer controlled 5.0's have a knock sensor.

Rev

Skyman knows
 

Hey, Skyler, I know that you are familiar with this question, so chime in.

Rev

sry bout the knock sensor 5.0 no got! worked on to many GM cars this week:rolleyes:

Can easily be wrong here
 

Late model 5.0's and 4.6's are not something I'm really familiar with. I did think the later 5.0's with computers had a knock sensor. I can easily be wrong on that. If I stand corrected, I can certainly accept that.

Rev

Er, it's on my '95 V6... I know it's not a Windsor, but I figured it would conceptually be the same. No mods, have no idea what the timing is set at, and for the V6, I use the recommended 87 octane...

It's been happening for a few years now, and now I want to get to the bottom of it!

I can't even find one of the V-6.

As far as I know the 4.6 DOHC is the only motor in the Mustnag line that has a knock sensor.

-Josh, aka the tireburner

Dont want to be to negative but my experience is that a noise that gets worse under heavy load or brake load is one of three things if not detonation. 1. Main or rod bearings 2. Broken piston ring 3. Wristpin
If you have heard detonation before you should be able to tell if yours is different. Deep noises under load can be a sign of bearing trouble.

Hope its not though!

I hope it isn't either... Then again, I put 132K miles on that 3.8, oil changes every 3K, but I wouldn't be surprised. It hasn't gotten "worse", so I'll just keep my fingers crossed and see how many miles I can get out of it!

That's my winter car ya know! :D

Some things that can cause pinging/detonation:
poor quality fuel
overadvanced timing (or too much timing for gasoline)
plugged injector(s) - running lean in one or more cylinder
plugged fuel filter/low fuel pressure - not getting enough fuel volume under load
carbon buildup - decreases chamber volume increasing compression ratio/heat in combustion chamber, also carbon built up on back of valves can soak up fuel - mostly when cold and cause engine to go lean on one or more cylinders, ping under load.
at part throttle a faulty EGR system will cause the combustion temperatures to increase causing ping (going lean).

This is what i'd try:
change the fuel filter (if not done within last 15,000 miles) and change the grade of fuel to premium and see if there's any change. If it goes away with better fuel then i'd suspect either poor fuel quality or carbon buildup.

Good luck, hope this helps