Engine Knock for Short time after starting car during acceleration
 

Hi all-

I get a little Engine Knock for a short time after starting my car when I accelerate or go up a hill. I do not hear knock when it is just idling or if I am only slowing accelerating (only when I give a little extra gas). After the car has been running (and me driving)for maybe 5 minutes the car will not knock anymore when I accelerate or stress the engine (it goes away). The noise is consistently there after I start the car (and am accelerating while driving) after it has been turned off for any length of time.

The noise is not very loud but I do hear it and was wondering if this is typical of G35's (07+). it may just be how these engines work when cold and warming up :). it has been this way since I got the car (new). I am at 800 miles now and have had the car 6 weeks.

Thanks!

Are you using Premium fuel?

yes. 91 octane which is the best cali has. I only hear it for a few minutes after starting the car up and driving and only when accelerating moderately.

That's not right. did you check your oil level. It sounds you are running on low. Do you warm up your car before you drive it every morning?

TG

Yes I do warm it up.

How is the oil level?

TG

Just checked and it is normal (and very clean). The knocking I hear does not happen after starting the car while idling. It only occurs for a short period of time after having started the car when stressing the engine by accelrating a little hard or going up an incline. It is no longer there after a few minutes of driving.

To help describe it more fully if I rev the engine at idle after starting the car I do no hear knock. I only hear it during a short time after startup when I put a little stress on the engine accelerating harder or going uphill.

Hm. I would say it has something to do with your gas. Try to pump gas somewhere else or maybe to use some octane booster to see if it helps.

TG

I will give that a try. I have only gone to the same place since I bought it (Phil 76 or Exxon I think).

take her to service.

It sounds to me like it's the other noise people reported (and I have) it's not a knock, but it's a metal sounding noise, very different then after the car has been opened up and drivine for a little while.

I think it has something to do with the exhause or intake being open... it has this metally throaty pingy sound for the first few minutes of throttle... even if the car is warmed up.

Thats what I was thinking. Mine does it, sounds like a rock stuck in the exhaust until it warms up.... Comes from under the front seats, or so it sounds.

Haven't heard this on my G35 yet, but my Discovery does this. I know, entirely different and ancient engine, but the symptoms are exactly the same. Dealer said it's normal (even though not all of them do it) and I still haven't figured out the issue. Does it sort of sound like a diesel engine? I say it's either an oil issue where the oil isn't getting to where it's supposed to be fast enough, or a part tolerance issue that goes away after the engine warms up because some part expands more than others with heat. What grade engine oil are you using? Maybe someone mistakenly put in 20W-50 :eek:.

A lot of other vehicles do this, mainly when it's cold outside. My suggestion would be to take it to the dealer. They may have to keep it overnight so they can try and listen in the morning. Even if they say it's normal, at least it's on record that you've reported the problem. This may help out in case there are related issues down the road. In the mean time, warm the engine up a bit on first start and take it easy for the first few minutes.

Is it ticking, or true knock?

Do you know the difference in sound?

When I was tuning my last car, you could hear real KR, it's an uneven ticking sound. (sporatic)

If the ticking is evenly spaced then it's likely something else.


My first thought (since it happens before the car is warmed up) is that it's emmissions control crap. Exhaust Gas Recirculation (EGR) or something like that.