'99 F150 4.2l Cat & Acc Pwr -exh

[wdsmithjr]

Posted this under the truck section but got no response, so I'm trying here:

I have a cat that you can hear the insides rattling around on the pass side. I know that both on that side has to get replace together. Should I replace all 4 too? Found them on-line for $494, local shop wants $1403 parts and labor to replace and I'd still have to replace the rest of the pipe, muffler and tailpipe. I read somewhere once that one reason they break is because of fuel mixture is not correct. Could it be that too or just age? Truck runs good.

Also, my cig lighter and access. plug kept blowing the fuse. I tried getting my codes pulled at advance (due to bad o2 sensor) but they couldn't read from the obd connector. Found out in the book last night that the obd conn and cig lighter uses the same fuse. I replaced the cig lighter, access. plug and put in a new fuse. Cig light works, will have to see if the obd conn works now, but the access. plug still dosen't. Any clue as to where/what to look for to get it to work again?

The guys at advance told me that if they cannot read from the obd conn that the trucks computer is going bad. Have a hard time believing that. Any and all suggestions would be welcomed.

Thanks for your time.

[Bear River]

You can replace those as a side. There is no reason to replace both sides, the fuel management is handled as seperate banks. Also the 4.2L works harder than the V8s, so the cats do fail slightly more often in my experience on the 4.2L than on the 4.6 and 5.4.

The truck may run fine, but the fuel management can still be off enough to cause the cats to fail. Age is irrelevent, the cats are literally designed to last forever. The only fail when something else causes them the fail, most often overheating and incorrect fuel management.

If the OBD-II plug doesn't read, it could very well be a blown fuse. When you have the scanner on and running, you will obviously want all codes, but have them retrieve the long term fuel trim as well. That will tell you whether or not the truck has or has had a fuel management issue.

[Bear River]

Quick question, is your vehicle 2WD or 4WD, because it matters. If the ones you found on the internet did not ask you that question, there is a 50% chance that they will not fit your vehicle. Also, where are your rear O2 sensors located.

[wdsmithjr]

Thanks for the reply. Its 2wd. The rear o2's are located right after the last cat (on each side) before the cross over pipe that connect the two sides before going back. I take it that either the dealer or a mech. with a good scanner can pull the long term codes. To adjust the lean/rich, is it done thru the computer? Or is there a "manual" adjustment? I can work on the older cars/trucks but these with computers and efi are a bit beyond me. Guess I need to get some books are start learning about them. Will have someone pull the codes after I get the parts and put them in. Thanks again.

[Bear River]

The computer contains a set of fuel tables that tells it how much fuel the engine should need in each load range under various conditions. The O2 sensors detect the actual amount of oxygen in the exhaust, and the computer will make small changes to the amount of fuel it adds. This will show up in the computer as the fuel trim data, which is basically the amount of adjustment that is needed. If the vehicle is running properly, the fuel trim will be within 2% of zero on the long term data, though as much as 3% is acceptable. If it is more than 3% plus or minus, there is a long term fuel management problem that was most likely responsible for the converter failure.

[kens64]

Not sure on this, but isnt the emissions warranty still valid on your truck? You should be able to get your truck fixed for free by Ford. Its seperate from your regular warranty and its at least worth checking on.

[Bear River]

Yeah, check with the dealer, you have an 8 year 80,000 mile emissions warranty which you might still be covered under.

[wdsmithjr]

Will do, but I image they'll shoot me down, trucks 9 with 108k. Never hurts to try though. Drove it last night, whew what a racket. Definately need to go. wonder if I could replace them one evening after work. Supposed to take it camping this weekend.
Thanks for the info.

[Bear River]

Ok, you are out of the warranty, sorry dude.