[marineo1]

Hello everyone, I'm the owner of a 2007 Subaru forester and since I bought it I've noticed that when the engine is warm and under load I hear pinging noise coming from the engine, I advised the service department of this problem and they told me that is normal that the engine does that....WHATTTT???? I said... I was wondering if any of you out there has or had the same problem and how yous went about to fix it or have it fixed. I know for sure that a pinging sound coming from the engine is not anything good b/c I feel that the car lacks of power while this problem appears. Please help.
Thank you.

 

[craigbhp]

What model Forester do you have? Also was it a Subaru dealer that told you the noise was normal?

 

[Nick D]

Misfire you think?

 

[Papa_D]

Can you record the noise and post it?

 

[stan_t]

X or XT? Try the highest octane fuel to see if it goes away and go from there. People have reported this many times on this board.

Stan

 

[marineo1]

Yes was the subaru dealer mechanic that told me so, the model is 2.5 X

 

[marineo1]

I'm will try to record the pinging rumor, although is not easy b/c I would have to drive it and it only happens under accelleration. will see

 

[marineo1]

I've been getting high octane fuel from quite some time now, the dealer's mechanic told me so too. but still the problem is present.

THANK YOU EVERYONE.

 

[marineo1]

Misfire I wouldn't say, my friend is a good mechanic and told me that could be the knock sensor, I don't know if this car has one but I know the this car has 5 years power train warranty so I'm ok for now but I hate to beat on the engine. It doesn't do it all the time, but I'm starting to realize that it does it more often the b4.
Thank you.

 

[4str]

The user's manual says it isn't unusual to hear it from time to time.

I read once that your engine is actually getting its maximum mpg when there is light pinging.

 

[TheEmrys]

No CEL codes? I had a bad "ping" that turned out to be a loose exhaust manifold. It would knock just like an engine. The real kicker is that it fooled the CEL, too. CEL through a bad knock sensor. I replaced the knockc sensor and still had the issue. I tightened up the exhaust manifold (to 20 lbs I believe) and it went away.

 

[stan_t]

Is this car a 5-speed? What RPM are you at when this is happening?

Stan

 

[marineo1]

It's an outomatic transmission model, and it usuallu happens from 2500 to 3500 RPM

 

[Papa_D]

Try the rubber hose and Styrofoam cup trick to see if you can hear it pinging while in gear with some load on the engine. Just put the emergency brake on and put your foot on the brake hard also and then gas it while in gear to place load on the engine to see if you can hear if, but preferably do it somewhere that is safe if you get some lurching forward.

Good luck with it and were it me, I would not just ignore it altogether, I would try to find the cause and stop it as much as possible and your friend may be right because if your knock sensor is bad, it would not retard the timing under a detonation condition like it is supposed to and I would be quite surprised if our vehicles didn't have knock sensors.

It is also very difficult to sense detonation while an engine is running in an remote and insulated dyno test cell. One technique seems almost elementary but, believe it or not, it is employed in some of the highest priced dyno cells in the world. We refer to it as the "Tin Ear". You might think of it as a simple stethoscope applied to the engine block. We run a ordinary rubber hose from the dyno operator area next to the engine. To amplify the engine sounds we just stick the end of the hose through the bottom of a Styrofoam cup and listen in! It is common for ride test engineers to use this method on development cars particularly if there is a suspicion out on the road borderline detonation is occurring. Try it on your engine; you will be amazed at how well you can hear the different engine noises.

Engine Basics: Detonation and Pre-Ignition: Streetrod Stuff

Detonation is not necessarily destructive. It's not an optimum situation but it is not a guaranteed instant failure. The higher the specific output (HP/in3) of the engine, the greater the sensitivity to detonation. An engine that is making 0.5 HP/in3 or less can sustain moderate levels of detonation without any damage; but an engine that is making 1.5 HP/in3, if it detonates, it will probably be damaged fairly quickly, here I mean within minutes.

Detonation causes three types of failure:

1. Mechanical damage (broken ring lands)
2. Abrasion (pitting of the piston crown)
3. Overheating (scuffed piston skirts due to excess heat input or high coolant temperatures)

The high impact nature of the spike can cause fractures; it can break the spark plug electrodes, the porcelain around the plug, cause a clean fracture of the ring land and can actually cause fracture of valves-intake or exhaust. The piston ring land, either top or second depending on the piston design, is susceptible to fracture type failures. If I were to look at a piston with a second broken ring land, my immediate suspicion would be detonation.

Another thing detonation can cause is a sandblasted appearance to the top of the piston. The piston near the perimeter will typically have that kind of look if detonation occurs. It is a swiss-cheesy look on a microscopic basis. The detonation, the mechanical pounding, actually mechanically erodes or fatigues material out of the piston.

 

[stan_t]

There should be no knock to begin with for the knock sensor to pick up, something is wrong. Car should not knock on high grade fuel.

Do you usually drive the car pretty easy? How many miles on the car?

Stan