slanter

My 98 Cherokee sport has been making some really strange noises. Firstly, it started making a strange screaching noise intermittently if you rev the engine up (not even dramatically, just up to like 4k but quickly. I took a small trip to a gas station nearby and tried revving it to get that noise, and I got it for sure... eventually it stopped but the engine kinda sounded like... like someone had a metal bucket full of rocks on top of it. And to add to the strangeness I went to turn the engine off and it wouldn't turn off! It just klunked like a single-piston diesel or something. Finally I just babied it back home and the engine finally turned off... whereupon I turned the ignition on again it it's sounded perfectly fine.

Here's a link to a video I took while the engine was idling at the gas station with the weird scratchy sound and then the noise it makes when I turned off the ignition.

5-Speed

That sounds like your starter is engaged.

BlueRidgeMark

Yep.

But if my engine ever made a sound like that, I would shut it off so fast it would make Flash Gordon look slow.

fb97xj1

I say starter also. Thats the same sound you get when cranking the engine over.

slanter

haha, my first reaction WAS to turn it off... and it wouldn't turn off, it just made that noise and as soon as I put the key back in the run position the engine would sound almost normal. Today I managed to get the actual noise that was the predecessor to this happening to see if anyone can identify it. About six months ago I started having issues with my ignition (key wouldn't turn in the ignition unless I smacked the key with a screwdriver) so I'm wondering if it might be ignition related but it doesn't seem to matter which position the key is in.



Edit: It doesn't seem to happen when the car is in neutral, I revved the heck out of it and didn't get any sort of screetching noise.

BlueRidgeMark

There are a number of reasons your starter might engage when you don't want it to. Stuck relays are one, and that problem can be intermittent. But the ignition switch is another possible culprit.

97grand4.0

I saw something in the FSM about how to stop a 'runaway' engine, it said spray fire extinguisher under the front grille where the air intake is.

BlueRidgeMark

That's either a really good idea, or a really bad idea, or a risky idea. It all depends on what kind of fire extinguisher you use.

• If it's an inert gas, like HALON or CO2, great. It will put the fire out and will not bother your engine at all.
• If it's dry chemical, it will destroy your engine.
• If it's water, it may hydrolock it, bend some rods or push rods, or you may be just fine. It's a gamble with the odds heavily against you.

A much safer way is to yank the air tube off the throttle body and just put the palm of your hand or some other flat object over the intake. It will shut down pretty quickly, and no, you aren't going to have your hand sucked into the engine.

I did this for a friend whose Mercedes had run away on him. It wasn't over-revving, but it would not shut off. He drove it to the dealership, but this was late Friday night. I met him there and shut it down with a paperback. The shop had him squared away in a half day, and no further problems. I've seen it done on a huge (1200 ci, 1500 hp) air-cooled gasser. The air intake was maybe 10" diameter.

It works. Don't be afraid to try it if the need arises. Much safer than disconnecting a gas line.

Pulling the ASD relay should do the trick, too.

97grand4.0

I think it said CO2. I was thinking the same as you after I posted that.