Engine ticking noise when accelerating under load

MOTORHEAD90

MEMBER
2008 INFINITI G35
3.5L
V6
2WD
AUTOMATIC
150,000 MILES

Upon acceleration always under load when driving up hill at low RPMs 1-3000 I will noticed a ticking or tapping noise. It's not the catalytic converters for sure because those used to rattle loudly at idle until I replaced them both recently. Now I'm on to my next major repair (I'm sure) fixing my engine rattle. Sounds like it's coming from the rear of the engine closet to the dash. Any advice would be appreciated to give my mechanic a direction to head in. So he's not just throwing parts at it or dismissing it as trivial.
Thank you,
- Lenny in A.Z.

1 Reply

KASEKENNY

MECHANIC
18,907 POSTS

This could be a mechanical issue as you suspect but I would put more weight on it being a spark knock or detonation.

Basically as you are accelerating this is prime time for spark knock to come out especially if you are on an incline and not pressing the throttle that heavily.

So normally spark knock will go away as the RPM comes up or load on the engine changes.

The knock sensor is supposed to pick this up and adjust the fuel mixture to compensate but it does not always do that.

https://www.2carpros.com/articles/how-a-knock-sensor-works

I would suggest starting with checking for codes.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

If there are no codes then the next thing I would do is let the fuel run down and then fill it with about 10 gallons of high test fuel, and purchase a bottle of octane booster.

Then run the vehicle a couple hundred miles and see if this noise stops or gets better.

If it continues getting worse then clearly this is not it.

Also, can you get a video of the noise as we should be able to get a good idea if this is the noise after hearing it.

Thanks