Rattling when accelarate

[JoergM]

Hi,

I am new here and sorry if this has been discussed before. I just bought a 2002 Jeep Grand Cherokee Limited with a 4.7 engine (I am not sure which type it is since I read that there are 2 types). The guy from which I bought the car had it highly customized (lift, Tyre's, etc.) as well as put it new engine with 10,000 KM only.
However, he left the car stand around for about a year without moving it a lot. It has its rusty areas but that is ok and I can take care of it.

However I realized something with the engine. After 5 minutes of driving, when I accelerate, particularly if I really push down the pedal the engine sounds almost like a diesel. It goes away if I release the pedal again and just cruise. I reckon these are the valves.
Funny things is that I don't hear the noise if the car is not moving (if the I am in 'N' or 'P'), then I just hear a nice roar which I would expect.

The car was a bit low on Oil which I corrected, but what baffled me was that there was a lot of dried, burned stuff inside of the Oil cab when I opened it. Could it be a combination of the car not getting moved and the valve just are 'dirty' with some burned oil stuff (or whatever you want to call it). Or do they need some re-adjustment?

Any idea what this can be and how to correct it?

Thanks for any input.
Joerg

[Classic Boy]

What you describe sounds a little like worn big-end or little end bearings..
I would maybe seek out a reliable local mechanic and ask them to diagnose.

It is common to find coked looking oil stains on the underside of V8 oil cap

[Hoobz]

My first thought was loose exhaust manifold bolts

Hope like crazy it's that and not bearinks

[Notso]

Put it in top gear and slow down to around 20kph. Push hard on the accelerator. If it rattles then it's probably main bearings.

[Grippy]

How far have ya driven it since getting it? How much fuel have you put in it? Could be old shit fuel and the thing is detonating

Sent from my SM-G930F using Aussie Jeep Offroad mobile app

[JoergM]

Thanks a lot for the replies.

I am currently traveling but will be back on Friday and then report back.

I had the impression that the rattling really starts after the engine is getting warm. Right after start it is barely recognizable.

And what I also realized is, that if I am just cruising and then slightly push the pedal for a short moment the rattling noise appears just to disappear again unless I am really pushing hard.

[skipperau]

If you need a hand when you get home there are a few of us in Brisbane, I’m on the south side, and a few scattered all over The place, I’m sure someone would be happy to pop over and help you out with a diagnosis