I have a 99, 5.4 f150 with 99600 miles; I get strange cracking and chattering noise right around transmission and catalytic converter area when I park my car and continues like 5 to 10 minutes, I’m suspecting it is the converter but I’m not sure. It has never happened to me with any of cars I had before. Anyone have any idea what could be the problem?

 

Off hand it sounds like the converter cooling down after you kill the engine.

 

I took my truck to muffler shop over the weekend and converters needs to be replaced, there are two and they are very expensive, the muffler guy was telling me that he can just cut the converters and put straight pipe instead of converters, would that cause any problems? I’m not sure what is the function of converters; I just don’t want to harm anything on the truck.

 

Iv been debating cutting mine of for months, as I have one of them rotten and ford Quoted $900 to have it replaced. Looking elseware and will probably deal with it in the spring when I can cruise with the windows down, and it really starts to bother me (the rattle)...

The cats have an O2 sensor in them so cutting them off would produce a check engine error, or atleast thats what browsing the forum as led me to belive... But let me know what you do, as Im going through the same problem and am always looking for sugestions, theres no way im paying $900 for a new cat... but its law to have em...

 

that O2 sensor can be a real problem. it will cause your check engine light to come on and, depending on how the computer resonds, can have a huge impact on performance and mileage. however expensive it might be, your best bet would be to replace the converters.

you might want to see if you can pick some up at a scrap yard.

good luck

 

Once a vehicle has reached a certain age or mileage, which I naturally can't recall right now, it's ok to replace factory cats with aftermarket cats. Should be cheaper, and will allow your Expy to pass any state vehicle inspection process that include a visual verification that all emission equipment is in place.

 

I have this same sound too, except mine comes a about 2 minutes after I start the truck. Have y'all come to the conclusion that it is definetely the cats? My sound is coming from about the same place...right about where the rear cat is on the driver side.

 

Yup, thats the one thats cusing me problems initialy thought it was my transmision, as i could only reproduce the sound when I torqued the engin a bit attempting to climb a speed bump.. but after crowling under it, and having the parking break on, and somone very trust worthy stick it in gear and bring the RPM up, i was able to conclude the Cat.

Talked to the ford dealer, said it coud just be the heat sheild, sooo bought there $12 giant hose clamp, figured what the hell.. tried that, naaaada.. after a closer inspection, its within the heatshield,... I can use a screwdriver and push the lower end of the Cat pipe inword through the vent spaces in the cat...

I wonder what that age/milage is for Vancouver, BC.. i would love to switch them out aftermarket ones, or even just straightpipe it.. but If I recal, our law states something like "if origianly equiped, must still be functioning".. I guess Im out of luck for a cheap solution..

 

Thanks for confirming that. I'll probably take mine into a muffler shop to see what my options are. If the cat does turn out to be my problem, which I'm pretty sure of since you're having the same sound, I was thinking about just configuring my whole exhaust system from headers back from all new parts. That way I wouldn't have to get factory Ford cats and hopefully it'll be a little cheaper...not to mention the power increase I hope I'd gain.

 

There are tampering laws, feds and state, that prohibit removing cats. And we sure wouldn't want to violate such lofty laws. Anyway. There are two sets of O2 sensors. The front or pre-cat sensors are used to determine how much fuel to inject and wouldn't be affected. The truck would run just fine. The rear or post-cat sensors are used to monitor catalytic converter efficiency. They ONLY set the light and codes for catalytic converter efficiency low. You could plug the hole and leave them hanging and they probably wouldn't set a code (nice and efficient job of smoothing rich/lean signals in the air). Or there are O2 sensor eliminators you can buy specifically to fool your truck's computer. Google will find them for you. For instance, the first hit for "O2 sensor eliminator" found:

AFX Down Stream O2 Sensor Eliminator 1999 to 2001 $64.95

This plug-in Simulator is designed to eliminate the SES codes associated with the post-cat sensor on Neons 1999-2001 with round plug. You unplug the down stream 02 sensor, then plug in the Eliminator, and rear sensor can be completely removed from the vehicle. You will get no check engine light for the downstream 02. You can run without cat, and the computer thinks it is still there. FOR OFF-ROAD USE only.



I'm sure most of us have 1999 Neons we use for off-road. A common conversion. You get the idea. Or just remove the check engine bulb.