Help! Engine Knocking

[philw349]

I just went to go to the store and started the car and the rpms hovered between 500 and 800 and made a rumbling noise and didn't stop. I can tell something is wrong.

I checked the oil level and coolant level, those are both good. I'm thinking it might be oil in the plugs. It's been having lack of power lately and theres some oil around the valve covers. Any other thing to check? The engine was pretty hot to the touch, moreso than usual. Thats all I can thinkof.

<small>[ February 21, 2002, 07:19 PM: Message edited by: philw349 ]</small>

 

[DeaconBlue]

Is the oil light on or flickering ?

 

[philw349]

Ok I just went out and started it again. The rpms seemed a little jumpy but then stabilized. No engine light or oil light. It idled fine for about 4 minutes and then I shut it off. I'm thinking oil in the plug wells. The strange thing is, the plug boots dont seem to be bathed in oil. Theres a little grit around them (which I'm gonna remove with a vacuum) but not much oil. Oil is seeping from the upper valve covers though.

<small>[ February 21, 2002, 10:32 PM: Message edited by: philw349 ]</small>

 

[sdpatt]

The idle behavior and rumbling sounds point to the fuel return line check valve not holding the return line pressure. Check this out by turning hte ignition key to ON (not starting) and listen for the rumbling from the tank. If, after several turns of the key, the noise stops, try starting the engine. If the idle is normal (900 rpm), then that would confirm my guess.

 

[Prophet78]

Sounds like a bad cat to me. I had the same problem with my cats when they went. I did notice that you have the SS y-pipe. How old is it? If you have the stock pipe around, put it on and check to see if it fixes the problem.

-Jeremy-

 

[philw349]

Update, this is unusual, but while trying to replace something else under the car me and my brother noticed that my K&N filter was very loose. And it wasn't just loose, it was completely off and flopping around! I think this was part of the problem. I think the K&N was getting sucked into the fender snorkel and the engine was stumbling to get air. The problem hasn't come back yet. After reattaching the K&N the power seems good so far. I tried turning the key a few times like you said Scott and it gave a normal whine from the fuel pump. The rumbling was coming from the engine itself, like it couldn't completely startup but wouldn't stall either. It still could be a catalytic converter issue, the Y-pipe's almost 3 years old. Thanks for the ideas guys.

Something people should know, the K&N filter on the SS intake needs to be checked every so often, cause it can come off (unless I'm an extremely unlucky person). I think we caught it just in time but it could've turned the car into a vacuum cleaner. eek!

<small>[ February 23, 2002, 02:11 AM: Message edited by: philw349 ]</small>

 

[sdpatt]

The rumbling noise comes from the fuel tank where the vaporized fuel is bubbling up through the gas in the tank.

Scott

 

[philw349]

Uh oh, its back. My theory was wrong. Today when I was leaving it started stumbling again, but not as bad. It was hanging between 600-800 rpms this time. So I turned the key a few times and I heard what sounded like farting noises coming from the gas tank. Props to Scott for identifying this. Thanks for the info once again.

<small>[ February 27, 2002, 11:53 PM: Message edited by: philw349 ]</small>

 

[luigisho]

The check valve is a dealer only part as far as I know. It's very cheap but if the parts person is lazy they won't be able to find it. I posted the part number somewhere so run a search. Install isn't very difficult but you have to drop the tank to get to the fuel pump and sending unit. I would advise that if the pump is old you should consider replacing it at the same time to avoid ever going back in there.