This may or may not have been brought up in prior post but I couldn't find any information on it.

Since I have had my truck, approx. 1 1/2 years, now has 30,000 miles on it I have always noticed that the tail pipe has carbon build up on it (black). I am not as knowledgeable as most you are, but have heard and understood carbon build up to be due to running rich. Is that correct?

I have noticed this on other friends Ford trucks as well, be it the 4.6 or 5.4. Mine is a 4.2. My question would be is that how they come from the factory, running rich? If so is there a benifit if it was to run a little leaner? (I would imagen a little better fuel mileage, but any slight improvment to HP or Torque?) How would someone go about making the truck run leaner? Superchip, air intake etc.?

The reason I have never really be concerned about it is my truck has always ran great, has great acceleration (I know a superchip would improve that) but no problems that I am aware of. It gets about 15 - 16mpg in winter (gas additives for winter) and about 17 - 20 during summer.

Any input is welcome, and I aploigize if this question may have been asked, or if it is not the brightess question but I always love to learn new things.

 

Hi 01,

This has changed quite a bit from what most of us grew up learning about this. It used to be that if you accumulated black sooty tailpipe deposits, you were running too rich, but not anymore.

Today's engines used unleaded fuel and different fuel formulations, have catalytic converters, fuel injection & computer control, so they have different tailpipe characteristics. Nowadays it's perfectly common to see those kinds of deposits on the tailpipe even with a brand new vehicle easily within a few thousand miles if not sooner. And, you'll accumulate more of them with shorter trips, shorter commutes to work, etc., though that doesn't mean that a lot of highway driving will eliminate this, it won't.

As long as you do not have modifications affecting the tuning that are not compensated for, and your O2 sensors are in excellent condition, your A/F ratios stay under control during closed-loop operation, which is anytime you're at normal operating temperature and at less than about 81% throttle opening. Once you go full-throttle, then you're in open loop & the PCM gets it's injector on time via the lookup tables, as during full-throttle operation there are no emissions standards that have to be met (a little known "secret" of the emisison laws).

All you have to do is feed & maintain your vehicle properly, making sure to change the O2 sensors every 30K-50K miles in addition to all your other scheduled maintanence, & you're generally in good shape in this regard.

If the tailpipe was accumulating *wet* sooty black deposits, that would be a different matter, but as long as it's basically dry deposits (other than the normal moisture in the exhaust during the first 10-20 miles of operation after a cold start), you don't have anything to worry about in that regard.

 

Thanks Mike for a great explanation. Yes my depoist are dry, and I maintain it well and like I had stated didn't notice any performance problems but wanted to ask the question.

I noticed you mention to change the 02 sensors between 30-50K is that considered just proper maintenace? I never thought about changing them out. Is it easy to do for the home mechanic? or is it wiser for someone like me, not alot of motor knowledge, to have done at the dealer? Whats the typical cost to have it done?

 

Hi 01,

Briefly.......................

They need to be replaced just as I said, at 30K-50K miles intervals. Pricing is really between you & whoever you have do the work or provide the O2's, but whatever you do, *never* try to save money buying cheaper OEM O2 sensors, use only the original Ford (Bosch) units. I'd say figure roughly somewhere around $70-$100 apiece usually is a good price on Ford or Bosch O2's.

It's the automaker's fault for not making those a listed maintanence item by the way, but the *real* reason they do it is due to the emissions laws. The automakers are respponsible for the emissions output of the vehicle long after the normal 36/36 bumper to bumper warranty is over, for a *minimum* of 50K miles, and the Feds are busy trying to extend that to 100K miles.

You can do the O2's yourself (though most people have their dealership do it), just use some WD-40 to spray the threads overnight before attempting to screw them out of the exhaust so they don't seize up. They've been subjected to terrible conditions and tremendous heat their entire life, so older units aren't always very easy to loosen up, hence the ole' WD-40 "trick."

Most vehicle owners never replace an O2 until the vehicle is exhibing very obvious problems, but that's a mistake, it's a normal maintanence item that by it's very design purpose, starts deteriorating the minute it's put into service, so don't let them go mroe than 50K.

Last, you only need to replace the 2 upstream O2 units as far as the engine is concerned, as the 2 downstream units are there primarily to check for catalytic converter presence & function.

Have fun,