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Discussion Starter · #1 ·
Base Timing 10 Degrees. With 87 octane I floor the car at 3xxx to 4xxx rpm
I get a rattle hissing sound coming from exhaust manifolds. It will only do it under hard acceleration. Half throttle shifting before 3000 rpm it will not do it.
When I run 93 octane it is very faint allmost impossible to hear. Car is stock.
Besides raising octane what could cause this?
Thank You
 

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this has happened to my car before 5.0 with a vortech, i kno its not the same as yours but it was doin the same thing as yours at like 3k on a 3rd gear pull it would detonate like crazy it was at 12* timing then i put it 10* factory thinking it would solve the problem....no. people have said to me different degree plug and just weather in general, hot days would kill my car, i know its supercharged and heat kills blower cars but, it would still do it. Ive even herd changing gear ratio to help the load on the motor. For the problem your having im guessing ####ty injectors maybe just get a tune or maybe somethin else, try throwin 94 octane in it if your around a sunoco in your area. I got my tune redone, the car is really really fat now, i have factory injectors in mine, i know its crazy right, it works though, hope that shed some light on the subject.
 

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Do a search in this forum for ping .
Youll see there are tons of suggestions I'll list a few off the top of my head.

First clean your MAF sensor element.
Check timing with spout out, you may want to try backing it down a couple degrees if you cant isolate it to something else.
Try some seafoam (Do a search)
Make sure your cooling is adequate.
Check for DTC's
Could be one of various sensors..
Fuel pump could be dying
Could be ignition related
Check for Vacuum leaks
and if you keep this thread alive do post back with a follow up fix as it helps others.

Good luck on your popular yet unpleasant journey.
 

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Another possibility - if it has the old stock balancer, it might have slipped, i.e. the inner half rotated on the outer half. Look for rubber sticking out between the inner and outer rings. Use a piston stop to find 0* at TDC and confirm it's pointing to that mark on the balancer.

Don
 

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Discussion Starter · #7 ·
All sensors replaced in feb.
clean air filter
new balancer
new ccrm
new distributer
new injectors
Basically everything under hood is new exept motor
No codes
I filled up with 93 octane from Sunoco with up to 10% ethanol no detonation under load.
I was talking to my buddy who is a mechanic for Trugreen.
He is having the same problems with there 2003 and up f350 gasoline trucks towing a 3500lb load going up the mountains.
He took it to the Ford dealer. Apperantly its the ethanol in fuel. It takes more energy to burn ethanol. If your car is under warranty they can reprogram your computer or you can send it off and pay 200 250 bucks for it to be reprogramed. The sound is from unburned ethanol fuel. Its not detonation or predetonation. Still not a reassuring sound:rolleyes:
They said to watch for up to 10% ethanol (little sticker) at the pump and use it. But if it says 10% ethqanol not to use it.
There is a gas station in Daytona, FL that sells old school gasoline for boats, antiques, and motorcycles. The 5ohhhs love that better
 

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sounds similar to the issue i had after i removed my egr system.

I removed the whole system and didn't realize i needed to let my ecu know that it was gone. i had it on the dyno and around 3500 rom it would start to detonate. I rechecked timing spout out at 10* and couldn't figure it out.

I did a little research and found out that the compter advances the timing dramatically with a working egr system. So instead of getting the car tuned for hundreds of dollars, i simply bought a harness plug-in that let the computer know the egr system was not working.

Problem solved...on the dyno i then put down 261rwhp and 304wrtq. Needless to say i'm happy i can drive my car again without fear of detonation.
 

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When was the last time the car was tuned up?
 
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