Running Rich, but no CEL 5.0 V-8

[MountaineerGreen]

My Mountaineer seems to be running rich. I can smell gas near the rear of my truck at idle. My tailpipe looks to be a little blackened on the inside. Im not buring any oil, no knocks, pings or CEL. Im only getting 12-14 mpg with the mods in my signature with the exception of the superchips tuner. Mileage has been pretty crappy lately, I think something may be wrong. I have new plug wires, plugs within the last 8 months. I sea foamed my motor a few weeks ago, I guess I could have fouled my plugs? But if that was the case wouldnt I have a CEL? Any ideas?

 

[ExplorerDMB]

You need to hook up a scanner and look at your fuel trims. Usually you want to see it either taking or adding fuel by 2-5%. You should look at long term, short term is too quick to get any accurate readings. Fuel trim should be measured at idle (for this test).

-Drew

 

[MountaineerGreen]

I used my tuner and checked my codes. I got a P0442. "Main Catalyst Efficiency below Threshold" What does that mean? I have had this code before and it threw a check engine light then, but now I have no light. I dont have access to a scanner to monitor fuel trims. What kind of scanner do I need to read those? Would the $100 ones at AutoZone work?

 

[MountaineerGreen]

Ok, to answer my own question, the P0442 code means something about the evaporation canister or fuel cap leaking. No biggie. I don’t have emissions tests here, so Im not worried about that. And the scanner at AutoZone wont work, it simply retrieves codes. Still dont know what to do about the running rich.

 

[Xzibit A]

is the truck running rough at all, id pull the plugs and check them i though you were supposed to replace them after seafoaming the enigne or something like that, you could have a fuel leak, such as a crack in the tank and that will cause bad fuel milage as well as a p0442 which is an evap leak(fuel vapor), these are probibly linked

 

[MountaineerGreen]

The truck is running fine. No idle or driveability problems except for excess fuel use. I dont have any fuel leaking or anything like that. I may try to look for hoses that are cracked or possibly replace the fuel cap. I will check my plugs tomrrow. I just hate getting 12 MPG when gas is pushing $3 a gal.

 

[Bill Kemp]

The evap. canister has a valve that can go bad and cause a fuel smell.
Check out the evap. system and you will probably find your problem.

 

[TheJMan]

My suggestion is to double-check your plug wires. Even though you said that the wires are fairly new, it wouldn't be a bad idea to double-check them. I put my TM headers on with a set of brand new wires and a week later the wire was completely melted despite using one of those heat socks. I worked on the routing of the wires and have yet to have another one fail, but I do notice on the blue wires that there is some darkening around the high-heat area even through the heat sock.

 

[MountaineerGreen]

I checked all of my plug wires and pulled a couple of my plugs. My wires are fine, I used OEM style replacements, so they have built on heat protectors plus my heat socks. My plugs are Bosch Platinum single electrode and they looked OK, but they were a little blackened around the tips. No heavy build up of soot or anything.

Could I have a weak coil?

I cannot find the evap. canister under the hood. Im going to do some internet research and see if I can find it to check on that valve.

I did notice I have some valve noise coming from my engine at most any RPM over 1500 with no load. I assume this is normal because it is a pushrod engine, I think I may be a little paranoid.

 

[410Fortune]

Your evap canister is under your battery, and then another back above your spare tire.
This truck uses two canister purge valves, one at both locations. One is called the canister vent and the other more of a traditional canister purge.

If you are running rich you should check the fuel pressure


Scantool.net is a great device for monitoring your computer, fuel trims, etc.

A gas cap code can often be cleared and may never come back.

 

[MountaineerGreen]

Ok I checked my fuel pressure, and it is 65 psi at idle. I put a new fuel filter on less than a year ago. I checked my exhaust again, and it dosent smell so much like gas now but still maybe too rich.

What Im so confused about is why I am getting such crappy mileage. I did all the mods so far in an attempt to improve my mileage. I dont drive heavy footed and mostly on secondary roads at speeds less than 65. I have stock size and style tires. What am I missing? I have spent tons of money on headers, exhaust, spark plugs and wires, fuel filter, air filter and sea foam. None of these things seems to help. I would have thought that the headers would improve mileage some, havent really seen that yet though. Someone please tell me what I am missing?

EDIT: Can faulty 02 sensors cause pour mileage without tripping a code? or maybe coil packs?

 

[410Fortune]

not likely that the 02 sensor would not set a code.

What is your tire pressure at?
12mpg is about right for an AWD V8 with your mods IMO, isnt 65psi at idle a bit high?
I am not sure as I am used to the 35-40 psi the 4.0L runs at idle (have not gotten into fuel system testing with the 5.0L yet)

 

[Turdle]

Yeah, sounds kind of high to me. should be 35-50 psi at idle, and actually more in the range you said 410

 

[MountaineerGreen]

Well what does that mean I need to do? How do you regulate fuel pressure on a computer controlled engine and what would cause my pressure to be so high?

I run my tires about 35 psi.

 

[410Fortune]

the FPR regulates fuel pressure via manifold vacuum unless ytour 01 has the retunless style fuel system, with this system as I understand it fuel pressure is controlled by the computer.

Some research is in order

 

[MountaineerGreen]

Im having trouble finding a site with the info I need. Maybe Ill ask at Autozone and see if they have it in their computer.

 

[410Fortune]

Call FORD

 

[Xzibit A]

first of all you need to change the plugs the 5.0s run best with autolite or motorcraft(made by autolite), the other ones dont hold up for some reason, i dont understand it but ive seen it many times and heard it by almost every mustang guy.

65 is to high and im pretty sure you have the returnless feul system in your 01, ill check on my 2000 though, but then its either your computer telling the FP the wrong amount, or the FPR is bad in the FP sending unit.

 

[MountaineerGreen]

I can change the plugs easily enough, but I cannot find a fuel pressure regulator on any parts website. Even Ford Parts Network does not list a fuel pressure regulator. What I really need is a souce for information to know for certain what the fuel pressure is supposed to be. Any ideas where I can get this info other than a dealer?

 

[Xzibit A]

yes lemme look i have acces to the ford service website, give me a few minutes