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-   -   Weird ticking sound coming from engine. Any ideas? (http://www.jeepforum.com/forum/f310/weird-ticking-sound-coming-engine-any-ideas-1001707/)

PurpleSplat 03-29-2010 07:21 PM

Weird ticking sound coming from engine. Any ideas?
 
I have a 2000 Grand Cherokee Laredo 4.7L V8 with approximately 148,000km. The oil is changed every three months (I never hit the 5,000km mark.) and the plugs were changed about 45,000km ago.

This past weekend while on a road trip, an odd ticking sound came from the engine when it downshifted going up hill while on cruise control. The speed the cruise control was at, was 110km/h.

It's hard to describe the ticking sound, but I suppose the closest thing would be sounding like a playing card in the spokes of a bicycle, but with a more metallic sound.

I've owned the Jeep for a little more than 3yrs and this sound has only occurred 3 times. Once a couple of years ago and twice over the weekend. Each time is was the same scenario.

The sound doesn't happen when I'm not using cruise control or accelerating on a flat road or uphill. The last time I heard something similar was in a 1986 Ford Mustang with a 2.3L engine and someone told me it was the camshaft. I wound up blowing the motor in it, and I don't want to go through that again, so I'd like to either get it fixed now, or trade it in before it becomes an issue.

Thanks for your help.

ronsaun 03-29-2010 07:58 PM

[QUOTE=PurpleSplat;9183763]I have a 2000 Grand Cherokee Laredo 4.7L V8 with approximately 148,000km. The oil is changed every three months (I never hit the 5,000km mark.) and the plugs were changed about 45,000km ago.
QUOTE]

i have a ticking also. usually it is a sticky lifter but this is not loud enough. i have been told it might be a really small exhaust leak. if you have a sticky lifter it will will increase on acceleration. if your oil is to low that will cause lifter noise as well. i would probably seafoam the crankcase and go from there. ron :wave:

Double E 03-30-2010 07:23 AM

Sounds like valve knock to me initially. I would check the TB, pull the air filter and inspect the plugs for needing to be changed.

It could also easily be water in the gas that's accumulated from the cold weather and parking in heated and non-heated conditions frequently. Where was the gas gauge each time it occurred?

Based on the above (and suspecting valve knock) I would (in order of cost & severity):

1. Add in a bottle of dry gas and use a higher octane fuel for a tank
2. Clean/replace the air filter
3. Clean the TB
4. Inspect/replace plugs

In general, it's a good engine. A few issues will make it dead before 300,000KM like low oil levels, bearing issues from poor OCI practices and overheating.

PurpleSplat 03-30-2010 06:52 PM

Quote:

Originally Posted by Double E (Post 9186804)
Sounds like valve knock to me initially. I would check the TB, pull the air filter and inspect the plugs for needing to be changed.

It could also easily be water in the gas that's accumulated from the cold weather and parking in heated and non-heated conditions frequently. Where was the gas gauge each time it occurred?

I didn't think to check the gas gauge when it happened, but it only happened on my road trips, so an educated guess would be at about half a tank. It's rare that I'd be under that... I like to keep the tank full and it's less of a shock when I'm at the pump.

I was planning on changing the plugs this year anyways, so I'll take a look at them. It's been about a year/15,000km since I've cleaned the air filter so I'll take a look at that.

There's some black sticky/oily residue in the throttle body right where the air box sits... The Jeep's been revving a little high at times and I have to kick it off to get it back to normal. I'm thinking that might be the culprit there.

I'll try your suggestions and see where it gets me.

chrism1367 03-30-2010 07:20 PM

if you are putting a heavy load on the engine (i.e. going up a large hill) could be just some predetonation, or pinging, had a car that would do that. Nothing major. And you say it has only done it a few times, that would make me think that that is what it might be.


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