The truck
03 Scab XLT
4.2 V-6
356,000 miles

Recent work
Water pump at 346K mi. (original)
New Motorcraft plugs about 1500 miles ago.

Codes
174=Lean bank 2
171=Lean bank 1
175=Rich bank 2 (note rich AND lean codes????)
316= Misfire first 1000 revolutions (whoop de do)
304=Cyl #4 misfire
305=Cyl #5 misfire
306=Cyl #6 misfire

The story, Yes it has a bunch of miles and I know they don't last for ever.

I was taking the Boy Scouts out today to teach a shooting class and all was fine until I started up Cajon Pass (a long grade for non So Cal people) and I noticed it didn't have the pull it usually has to climb the hill, thought headwind + load maybe. All was good and I got about 20 more miles down the road and it started loosing power and couldn't pull the speed limit. Checked gages and everything looked fine and CEL was on (not flashing but steady). Pulled over and knew it was misfiring. Checked the wires, and fluids. No oil in water or water in the oil, and no loose plug wires.

I pulled the plugs on the side of the road to inspect. Passenger side looked good for slightly used plugs. Driver side were damp, slightly black, and a little bit of build up on them.

I got the codes read, results are listed above, and checked it over a tad closer after being towed home. Plug wires look marginal but no arching (sp?). Also noticed a tick/rattle, used a stethoscope and narrowed it down to the rear bearing on the alternator (shouldn't be related to the misfires though).

My thoughts are to replace the coil and wires, this should take care of the misfire issue (I think).

As for the lean code I may be up for a set of isolator bolts/intake gaskets, but will check for vac leaks first.

The two points that have me confused are 1 misfire all on the same bank, and 2 a rich AND lean code for bank 2. Any thoughts to point me in the right direction are much appreciated.

Sorry for the long post but I wanted to be thorough. Thanks for reading.
Jim

 

But wait there is more!

New coil = no change

Vac gauge is reading low at idle, it's only about 13" and will go up to about 15-16, that can't be good. If I run the RPM's up to about 2500 (by ear) might be as high as 3000 the gauge stays steady then slowly starts to drop. That coupled with a throaty sound in the air box leads me to believe it could be a plugged cat.

Any pro's want to give me an idea if I'm headed in the right direction? Am I to the point that I should stick a fork in it and call it done?

 

I'd start at the most obvious and probably the cheapest, I'd replace the PCV including the rubber connector. If this malfunctions, you'll get all of the listed codes. This one fix MIGHT fix all of the codes. Use ONLY Motorcraft parts, cost is about 30 bucks for all of the parts.

 

Any mechanical ticks/knocks?

I don't know if id be suspect of the catalyst if it was "night and day" drop in power. They don't go suddenly clogged like that

 

I'd want to do a compression check pretty early stages of diagnosis to see if you can find anything, and a general health check of the engine

 

Take it to a muffler shop and get the cats tested. Make sure nothing is blocking the intake snorkel and tube, make sure the air filter isn't plugged.

 

Wouldn't that be nice and a good thought, I'm never that lucky.

 

Patman, it wasn't a night and day thing. I could kinda feel it coming on as it was beginning to get a bit sluggish.

It does have a tinny rattle to it. I have gone over everything I can with a stethoscope and can't nail it down, sounds almost like a flex plate rattle. Plus it does sound like it is coming from the exhaust pipe area by the fire wall.

 

That will be on the to do list.

 

I will try to round up a thermometer and let it run for a bit first so I can check the temp of the cats. That is one thing I looked at on the side of the road as soon as I pulled it over, they weren't red and no heat ticking coming from them. Maybe even loosen the exhaust at the manifold to pipe connection to see if it clears it out. I really do suspect the cats are the issue, we shall see!

 

Now the good news is I am not pressed for time to get this old girl ready to take me to work in the morning, I just got home from buying a new to me 2013 XLT Scab! Less than 25K on the clock and I got it for $24,000. Very clean truck with a Leer bed cover and Bed rug, and more bells and whistles than an old guy like me can figure out.

The bad news is if it is the cats, I'm screwed because it's a California truck and it MUST have OE cats to pass smog. Priced them and saw that one side for that truck are being given away for a mere $1500! That would work out to about 3 grand and here are your parts................Oh you wanted them installed? Just another thing I hate about living here!

Thank you to all that have given suggestions, keep them coming.

 

Sounds like it's time to retire it - I don't think it owes you anything!

If it is the cats, go get a PO box in Prescott AZ and register it there - and gut the cats. No inspection there. My nephew was going to do that when he lived in San Diego - he had a 08 F350 diesel that was stuck in regen and had a plugged DPF, but he got rid of the truck instead of gutting all the emissions crap.

Rather than depend on a thermometer, you may want to take it to a muffler shop that can actually measure the backpressure. I think they pull the O2 sensors and screw in a gauge. That tinny rattle is usually a cat internally self-destructing.

 

That might be the hot ticket George, I have 2 sisters that live in Kingman.......Might just look into that.