Jeep Cherokee is shaking and making loud noises

June 18, 2009 7:23 PM

2000 Jeep Cheroke Classic (92,000 miles) makes loud rumbling and shaking sound after starting, but only if it had been running shortly before starting. Also occurs very sporadically while idling.

If I run the vehicle, drive around for a bit, park it, turn it off, and then turn it back on within 15 minutes or so, the car will start fine but will then a pretty loud rumbling sound and will shake. The shake is noticeable but easily drivable while doing it. It goes away within a minute of driving, usually within 15 seconds.

If you turn it off while it's doing its shaking/rumbling thing, and then turn it back on, it will occasionally not do it.

All of this is pretty consistent.

Inconsistently, it will also do it randomly while idling. Very sporadic.

Up until about two weeks ago, it had the same problem but it was much quieter and hardly registered as a major problem. Not so much now, but I have no idea what would cause it.

posted by Anoxs to travel & transportation (14 comments total)

Some questions:
Does the noise get louder and more intense with the A/C on?

Does it make this noise when you're accelerating from a dead stop?

Does it get louder when you rev it up in neutral?

Is you Check Engine light on? If it is, does it flash?
posted by Jon-o at 7:28 PM on June 18

Oh, and what engine is in it?
posted by Jon-o at 7:31 PM on June 18

As far as I can tell, it has no relation to A/C. It does it upon start, whether the A/C is on or not. I think if it got any louder or more intense with the A/C on, I would have recognized it.
I will experiment a little bit more with it later tonight (and specifically double-check to see if it gets louder), but I feel pretty sure about this.

Never makes this noise besides in these few occasions, and only for that small period of time (less than a minute). Nothing I do behind the wheel seems to cause it. The noise itself is also consistent, and never seems weaker or stronger on different iterations of it.

Check engine light is not on.

I will test whether it gets louder when I rev it in neutral later tonight.
posted by Anoxs at 7:37 PM on June 18

Do you have the straight six engine or the V8?
posted by Jon-o at 7:41 PM on June 18

The engine is 4.0L 242 Power Tech I6.
posted by Anoxs at 7:42 PM on June 18

Jon-o: Fuel evaporation through/exacerbated by weak fuel pump causing a misfire?

OP: What do you mean by 'loud rumbling'? Loud 'not normal engine noises'? Or "loud noises in addition to normal engine noises'?
posted by Brockles at 7:43 PM on June 18

Loud rumbling is in addition to normal engine noises. I'm trying to decide whether rumbling is a good characterization of the sound, but it feels pretty accurate. But the engine itself always sounds like it's running fine.
posted by Anoxs at 7:47 PM on June 18

Check out this Cherokee forum http://www.cherokeeforum.com/
posted by patnok at 7:53 PM on June 18

I though hot start misfire at first, but there's no CEL. A miss that will cause vibration an loud rumbling would almost certainly set a code.

That 4.0 has a funky exhaust manifold that creates a noisy exhaust leak right where it bolts to the engine. I think that cylinder head is aluminum and the manifold is cast iron. After you drive it for a while and park it, the two metals cool at different rates and the leak grows. It'll be quiet at first, but it becomes increasingly loud.
Start the engine under the conditions that will cause your problem and listen under the hood on the drivers side (both the intake and exhaust manifolds are on the drivers side of that engine) and tell me if the noise is loudest there.
posted by Jon-o at 7:54 PM on June 18

loose spark plug wire or needs tune up. Do your basics & check out http://www.cherokeeforum.com/
posted by patnok at 7:56 PM on June 18

leaking brake booster vacuum line? I remember a thread on this in that jeep forum i referenced. log on & check out my jeep:-)
posted by patnok at 8:00 PM on June 18

I don't think that year Jeep has traditional spark plug wires. It has one big ignition coil/module unit that bolted to the head. A failure of that would cause CEL illumination for P0300 misfire.
A vacuum leak would trigger the check engine light and store a P0171 bank 1 too lean code.
posted by Jon-o at 8:10 PM on June 18

Really sounds to me like a short circuit in your ignition system causing two of your cylinders to fire at the same time rather than in proper sequence.

Looking at a parts site, they seem to have made significant design changes in the ignition for the 2000 model year.

I found this description of a fix for a problem that sounded a bit like yours:

Ignition Coil Pack OEM 4.0 Liter Cherokee 2000-2001
This is a OEM Ignition Coil Pack for a 2000-2001 Jeep Cherokee. 4.0L I6 If you have a Jeep With a Check Engine Light on and Mis-Fire Codes or still have a rough idle after changing the spark plugs and wires this might be what you need. Easy to install 4 bolts & a wiring connector. Easy to install & commonly needed after 60,000 miles or so. WE SELL THIS FACTORY ORIGINAL PART FOR MUCH LESS THAN THE DEALER LIST.

Featured Price: $199.95

Ouch.
posted by jamjam at 8:12 PM on June 18

No CEL, no ignition problem AFAIK.

Without knowing the model my first guess would be something to do with the fluids.
-How about an air lock in your water system? Anyway you can bleed the system?
-AC may not need to be on for the fluid to be circulating. Check it's fully charged.
posted by BadMiker at 5:23 AM on June 19