Truck runs poorly, need diagnosis help

Today under heavy acceleration in my 2.4 4cyl 5spd. 246,000 miles there was a loud clank at 3000 rpm and since then there has been very heavy valve slap, a rattle at 2200 rpm( kinda like a loose exhaust clamp), and a sputtering uneven idel. The valve slap occurs under any light acceleration and is a kind of muffled patter sound almost like that of an engine under strain. Could my timing chain be failing? Any help would be much appreciated.

Tmantstud

 

Could that one time occurrence cause this persistent problem? Could a clogged cat cause any problems? Neither of my O2 sensors work

 

I agree with the aforementioned. One of your camshafts probably jumped out of sync by a tooth or two. It would still run, and you would likely get that lopey, scavenging idle.

And when cats melt down in to a blob, they make a pretty distinct rattling noise in the cab. But I doubt that's the root of the problem.

Does the engine also sound like it's scraping and grinding near the front upon deceleration?

 

Yes it does have a scraping rattling sound under acceleration/deceleration usually around the 2250-2500 rpm range.

 

I have a feeling your timing chain is about to go. To see if it indeed jumped a tooth, get a cheap vacuum gauge, and connect it to manifold vacuum. Start the engine, and if the needle bounces around, you've likely jumped a tooth. If it holds steady at idle, it might be a rattling cat.

 

Ok, today with the help of a buddy I identified the rattle as a broken O2 sensor connector. The truck still drives weird though. There is a persistent muffled strain sound whenever i push the pedal slightly. In order to not make the truck make the noise I have to drive it incredibly gently, without depressing the pedal more than even an inch.

 

in that case...one of your cats may be clogged.

 

I definitely agree. You mentioned also that neither of your O2 sensors worked. Usually when O2's go bad, engines run rich, and send a lot of unburnt fuel in to a 1500 degree cat. That's when you get the platinum brick.

 

Wouldn't I have seen i major decrease in fuel economy if the cat had been clogged?

 

more than likely, but i have seen cats clog up, and there wasnt that big of a difference in mileage...depending on where the cat is located/if the o2 sensor is behind or in front of it.

 

Just curious, what kind of mileage have you been getting lately? I usually get around 26-27 in town. The best I've ever gotten was 31 on the freeway.

 

I average about 26-30 combined per tank. It hasn't changed as far as I can tell. I noticed that below the broken O2 sensor clamp there is also a broken muffler clamp. Could an exhaust leak make this sound?

 

Yeah, exhaust leaks usually make a loud "putt-putt" noise. Maybe the loud clank was one of the exhaust mounts giving way?

 

That's what I am beginning to think. Im going to take it by a shop to be put up on a lift to have the mounts re-welded and check for an exhaust leak. Thank you for all your quick feedback

tmantstud