Okay.

Here we go again.

I bought a 1998 F150 4x4 Offroad with a 4.6L engine recently. I've put about 3K Miles on it. It has a total of 99,500 miles on it. It runs like a champ. Has power out the rear end. I've heard that 4.6Ls have no power, I would like to call BS on this. I've driven several 5.4Ls and they simply do not have the acceleration this 4.6L does. I don't know why. Probably gears I'm guessing. (3.55s versus whatever the 5.4 comes with.)

Anyway. Here's the point. I'm getting P0420s like crazy. Right after I bought it, I replaced the REAR RIGHT O2 sensor. Drove it for a thousand miles or so, and the bugger came back. Come to find out, they didn't delete the codes from the computer when I specifically asked them to. So I figured it was a persistant code that came back to haunt me. I had them deleted. It worked great. For about 800 more miles. It came back. Today. Same single code. Truck runs great, no problems, getting 16 to 18 mpg depending on my lead weighted foot. I can throw a 700 pound quad in the rear end and it doesn't even notice it. Basically, I've seen no difference between CEL on and CEL off. I give, what's going on? If it were the cats I'd think it run like butt. It's not. Truck isn't missing. It's a daily driver of 72 miles a day at freeway speeds (55 to 75 mph). Has the power to get up and go around these pesky little freaks that go 12 on a freeway. I simply have no clue what's going on.

I was told P0420 (Bank 1 of 2) should be the front left sensor? I've heard it pointed to all four sensors, I simply don't know. Anyone shed some light on this?

Before you all go nuts jumping up and down that I need to use the search function, I tried. It's broke. It simply doesn't work. Blank screen upon searching (MODERATORS FIX IT PLEASE!)

Anyway.. that's the story. I'm sticking to it. Please help me out.

Thanks much

 

P0420 (and P0430) codes are not due to O2 sensors.

These codes come up when the OBDII test determines that the cats are no longer doing their job of cleaning the exhaust. Nothing more, nothing less. (Well, the oxygen storage capacity of the catalyst is being tested...)

Most expedient work-around is to install MIL Eliminators whch can be made for about $3 with parts from Radio Shack. Otherwise, you can replace the bank 1 upstream cat.... Of course, if you're not subject to emissions testing, you could just ignore it. This fault won't affect the engine in any way other than excess emissions.

Steve

 

how much are replacement cats?

 

Contact a dealer or look it up on one of the many online Ford parts sellers (google).

Steve

 

Okay. Thanks for the info. I know next to nothing on the newer vehicles for troubleshooting.

 

I'll have to jump in here with my 2 cents worth. My '98 P71 Crown Vic threw P0420/P0430 codes and that translated into cat efficiency below threshold. I didn't want to replace the cats so I did the MIL thing. At emission inspection time it flew through on the OBD II plug test. Just for kicks & giggles I asked the inspector (a friend) to do the sniffer test. All emissions were on the very low end of the requirements. I can only think now that the O2 sensors are bad and not the cats. The MIL eliminators were cheaper than the sensors and it DID seem to rum better after the MIL installation.

 

If the engine is already burning cleanly, there's nothing for the cats to do anyway.

If you want to see the O2 sensors in action, use a scan tool with graphing capability to watch the upstream vs downstream sensors switching around a good vs a bad cat, If you see the graph, the diagnosis is pretty clear.

The O2 sensors are pretty well tested before OBDII tests the cat's efficiency. O2 sensors are pretty low on the list of possibilities when a cat efficiency code pops up.

Steve

 

whelp. The bugger came back. Third time, definitely cats I'm figuring. Next few questions.

The first, I'm not paying 1500+ clams for new cats. That's crazy. Not gonna happen on my budget. At least right now.

1. How hard are MIL eliminators to make?
2. Should I completely remove the cats or just leave them there.
3. Is it going to hurt anything to leave them versus taking them off and cleaning them out and bolting empty cats back up?

 

If there is no evidence that the internal structure of the cat is failing, ie, crumbling or melting, that would cause it to either clog or restrict exhaust flow, there's little point in gutting or removing the cat.

GOOGLE "MIL Eliminators" . I found a nice set of plans that some guy had done on a little circuit board. However, it's really overkill and the entire circuit (1 resistor and one capacitor) can easily be hardwired then covered ih heatshrink tubing.

Otherwise, a set can be purchased for about $25-30 and installed into the sensor harness. Wires cutting and splicing will be required.

Steve

 

Will MIL eliminators work on a 1998 4.2?

 

Yes.
http://www.ponyexpressperformance.com/products.html is where I got mine several years ago.
Also see http://motors.search.ebay.com/MIL-el...r_W0QQfromZR40

 

Thanks, ncranchero.
I found plans to build yer own here: http://www.fordmuscle.com/archives/2004/12/Xhale/index.php#

Looks to be pretty easy. If it doesn't work, I'm out 5 bucks!

 

Thanks, that'll save me a few bucks next time I need them. Back when I needed my 1st set I looked and looked for a diagram.