If a plugs have not been changed on a 100,000 mile motor, like on my 2.8 v6 in my audi, could this cause detonation?? with no load on the motor, it runs smooth all the way through the rpms. with a load and hard acceleration (merging onto the highway) I can hear a det. sound or almost a ticking sound. not an exhaust leak, 'cause that would be heard with or without a load on the motor. any ideas??? would a bad knock sensor throw a code??? could a bad ECT sensor cause this problem??
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96 Audi A4 2.8 5spd
Airframe Mechanic, workin on the powerplant rating.
Anyone know of an apprenticeship position??
Detonation occurs when excessive heat and pressure in the combustion chamber cause the air/fuel mixture to autoignite. This produces many uncontrolled flames within the combustion chamber instead of a single flame. When these multiple flames collide, they do so with explosive force that produces a sudden rise in cylinder pressure accompanied by a sharp metallic pinging or knocking noise. That is what causes damage to your motor during detonation. Try changing the plugs and checking for performance gain.
By the way what kind of gas mileage do you get? What octane fuel do you use? Another thing it could be is over-advanced ignition timing or a defective knock sensor.
One other thing that can cause detonation inthe combustion chamber is debris in teh chamber, as one might get from crappy gas, or excessive carbon deposits. The debris heats up, under the pressure of teh compression stroke, and ignites teh air/fuel mixture from a point away from teh spark-plug, causing detonation when teh two flame-fronts meet. When this type of culprit is present you'll often het "dieseling" after you kill the motor. It appears to want to continue running...
I agree with flip. swap in some new plugs... Maybe run a couple-3 tanks of SOOPER-DOOPER-ULTRA-HIGH-TEST-premium along with your favorite brand of octane booster/fuel-line cleaner...
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the click noise is called pinking due to cheap fuel/gas or ignition timing problem ( 100k on a set of spark plugs well done ) knock sensor would throw a code but I doubt its that have it checked for fault codes or try better fuel/gas
if you have a code for your ect(electronic coolant temp sensor i assume?) (unless you meant EGT, then this post has no relevance) that could cause issues as well, the coolant temp sensor is a direct partner in determining your correct air fuel ratio. Example a shorted coolant temp sensor will tell the ecm it's -72(i'm not sure the exact audi parameter number) degrees out, and based on this temp it's going to be the engine too much fuel
I know the ect assists in determining a/f ratio, but I guess I was thinking that would just cause a rich running condition while the motor is cold. I currently have bremi wires and am about to go and pull a plug to see what the story is on them.
__________________
96 Audi A4 2.8 5spd
Airframe Mechanic, workin on the powerplant rating.
Anyone know of an apprenticeship position??
Detonation???
