Hello,

It's been a while since I posted, its always been a while since I have had a problem with my truck, and things have been oh to busy. I still read the posts though

The truck in questions a 1994 F150, 5.0L, 5SPD, 4x4

Lately I have noticed incredibly poor gas mileage, around 7MPG. I did a KOEO test, and managed to pull the following codes:

172 - HEGO shows system always lean
332 - Insuffcient EGR flow
556 - Fuel pump primary circuit failure

I had an endless amount of trouble with code 332, and I was under the impression I had cured the problem, however I am not so fortunate it would appear.

A read on an article somewhere that a faulty O2 sensor, could indicate the engine is always running lean, so the engine would attempt to run as rich as possible, causing the horrible gas mileage. The person who wrote it claims to have restored his gas mileage with replacing the O2 sensor. I've had a bunk one before, and replacing it did wonders.

Code 332 can burn in hell, I have replaced the EGR solenoid, valve, and sensor. I'm not sure why I am continuing to get the code, any help would be great, but I am honestly just done with that for now.

Code 556 indicates that I had a primary pump primary circuit failure. I am unsure of what this means, does it mean that the circuit is still currently broken, or it had just failed at one point. Where would be a good place to check to see if its grounding out? Any other recommendations on this particular code?

 

Im counting on you JustCallMeSean and Ymeski!

 

HI im not any of the people u ask for but about the oxygen sensor, its true about what u read on article . if the sensor its bad . it can send wrong signal to computer, and the computer try to adjust the mixture by pumping more gas, but if you truck its running too reach u can see it and smell it . do u see any balck smog coming out of tail pipe or do u smell any unburn gas.

 

Occasionally it smells of gas right after starting it. One problem I notice is that when the engine is completely warmed up it had a tendency to take much longer to turn over before it starts, it starts much better when cold. I think this might be because of a rich mixture. A cold engine likes a rich mixture, but when warmed up I think it needs something a little more lean.

I reset the trouble codes yesterday (reset the whole computer, left the negative terminal off for 10 minutes), and I havent gotten a check engine light on the way to work, I gotta do a longer drive later today, Ill see what codes come back up.

 

The harder time starting when its warm could also be an ignition thing. From what I've read a failing coil would cause that. I had that same problem, and sometimes it wouldnt start at all. Replaced my coil when I bumped my timing and it hasn't had that problem since.

 

A weak coil would also tend to leave some residual undetonated fuel to be read by the o2 as a rich condition. After I upgraded my Ignition system, a lot of quirky behavior disappeared. A side note would be to see that your PCV is functioning well & has a good seal where it mounts, where air isn't being pulled in from around it (the mounting grommet tends to harden, shrink & loose it's seal around the PCV over time. Insufficient EGR flow implies a Vac loss that isn't allowing full EGR function when called upon. It could also be argued than if there was efficient detonation in the first place, the o2 wouldn't be reading rich & calling for more secondary air from the EGR to balance the air to fuel ratio. The ECU will never stop in it's demand to function at 14.68 :1 air to fuel ratio. Whether a problem w/ excessive fuel being supplied, or inefficient fuel ignition, the ECU will demand more air to reach that mandatory ratio! And as you know, it won't shut up til it obtains that ratio! If you haven't figured this out by now about the ECU, It's primary function is maintaining that 14.68:1 air to fuel ratio. Drivability plays second fiddle. I don't remember if your MAP or MAF? If MAF, it could be fouled, reading within range , but not accurately, so clean it w/ MAF cleaner. W/ either one, MAP or MAF,a K&N drop in filter may help to increase air flow, but if a weak coil is the main problem, you won't actually be addressing the problem til you deal w/ that. What condition is your ignition system in?

 

The distributor, plugs, rotor, and cap are all less than 6 months old. The wires are in very good shape. The coil is questionable though, so I am picking up an MSD coil fairly quickly, and will probably get a new cap and rotor with it.

My truck uses a MAP.

I don't want to rule out the possibility of a faulty O2 sensor, so I am putting a new one in, and it never hurts to have a good O2 sensor in. The engine keeps telling me its running lean!

I'd appreciate any info on code 556, and if I should be alerted, or if it is something that might just take place the one time.

Could any of this be caused by a faulty fuel pressure regulator?

 

Oh, lean! Oops! Most of my yada yading was misdirected. If your upgradeing the coil, it will eat a stock cap and rotor pretty quick. you want to get some brass going there. MSD makes that cap that helps separate the wires coming of the distributor. If you have a lot of miles on your o2, I keep mine for around 3 years or 35K. A lot sooner than what's "politically correct". My manual lists #556 as a Fuel Pump Relay Primary Circuit Failure! If your lean & your seeing a code related to fuel (or lack thereof), you might want to look into it further. Could just be a sh*tty connection at the harness socket and that could show intermittently. Is it O or C or both?

 

556 seems to be a code I can't duplicate, for whatever reason maybe the circuit shorted when switching between gas tanks.

I just had the new 02 sensor installed and drove for about 50KM, I can't seem to get the trouble light to come back on (and it usually does come on after about 10km, if not sooner). Im hoping that was the problem.

Ill be doing the mod as specified in the commonly placed URL around here. Are copper plugs necessary for advancing the timing? I'll be getting an MSD coil, cap, and a rotor. MSD discontinued the wires for this engine, so Ill be getting some 9mm Ford racing wires (The drag shop says just as good if not better).

The codes are continuous, I havent done a running test. The system always blinks out 111 which is a system pass, and then 172 (HEGO indicates system always lean). I have reset my memory since, and I can't seem to replicate any of the codes yet. Im keeping my fingers crossed for the codes and that my fuel mileage increases.

 

I get the primary fuel pump circuit failure code sometimes too. Haven't figured out why or what causes it but it hasn't been a problem yet. I'm surprised ymeski didn't go into the Seafoam sales pitch, you probably should try it.