My truck has been running rich for a while. i have looked every where for a solution, with no success. it is running like it is missing a cylinder and exhaust smells like fuel. this is what i have done so far.

1. the spark plugs and wires look new.
2. the fpr looks new and is bosch. with no fuel in vacuum line.
3. the egr looks like it is working, but could not pull it all the way off due to the exhaust input pipe.
4. the injector are working correctly and are ticking right.

so what am i overlooking and what can i do?

 

Welcome to FTE!

You may want to check the PCV valve. If it is stuck open, your "Metered" vaccum leak, is now uncontrolled (even a bit more open even @ idle). I have many posts on how to check the O2 sensor allowing for an easier way of diagnosing a RICH or LEAN condition, if you have a good Digital VoltMeter.

Have you pulled codes? There is an easy way, that only requires a jumper wire and an Analog voltmeter. Try Ford Fuel Injection or read the Sticky @ the beginning of '87-96 Forum.

Another possibility is the thermactor system. Let us know what your results are and we'll try to help as much as possible.

 

well i just got a code reader and got a code 31 in the continuous memory. i am gonna try to unplug the o2 sensor and see what happens.

 

unplug it if it copntinues the symptoms with no change you found your culprit could also be the IAC TPS and or the TB had that problem with my 93 4x4 5.0

 

well i just unplugged the o2 sensor and it ran about the same not much better at all. so does that mean the sensor is bad? if not then what do i go to next?

 

i beleive so buddy

 

well i just checked the spark plugs myself, my mechanic said he checked them, and found that they were not torqued right and that they looked like they did not have very much spark. so i took the coil off and lo and behold it is stock from 93! so i am going to get it tested and see what happens. could that cause it to act like it is running rich when it is not? and would that also make it act as if the o2 sensor was bad?

 

One way I check the output of the coil, is to take a known GOOD plug, and ground it against the frame. Do you have a yellow spark or a blue spark? Yellow is weak, Blue is strong.

You can also disconnect the coil wire from the dizzy, use a long screwdriver or one that will fit in the end of the coil wire and ground it against the frame. Same thing goes for the colors. Even though it's stock from '93, it could still be good. I had a problem with a 2 month old MSD Blaster coil, and when I put the stock coil back on, the truck started immediately. The MSD coil wouldn't fire when cold, but would if I warmed it up with a hairdryer.

If in doubt about the operation or age of the O2 sensor, I would spend the $45-$53 for a new one. Just eliminate that problem all together. If you do a search under my name, you will find a wealth of info in regards to problems with either a RICH or LEAN situation.

Also, what plug gap are you running? If the stock coil is weak and you are running .56-.60, you could very well be runing rich. What plugs did you install or the mechanic install? Regular Motorcraft coppers' or Autolites? Anything other than those 2 will also give you problems, i.e., Platinums, Splitfires..

Hope this helps..

 

Sorry for the long delay, had to take care of a family situation. well i tested the plugs and they were good, and the o2 sensor is good but i still have a flood situation. i even tried to use a three stage fuel cleaner on it and it did not work. and the plugs are motorcraft coppers. the mechanic put them in for me at .044 calibration. what else could it be?

 

Do all of the plugs look the same? If you are running rich, you should see sooty black deposits on some or all of them.

You could have a leaky or sticking injector, but the condition of the plug in the affected cylinder would be a tipoff on this.

How about your coolant temperature sensor? If computer thinks the engine is cold, it richens the mixture. Plenty to read about that if you search on it.

Is there a rodent nest inside your airbox? It never hurts to check!

 

yeah they all look the same except cylinder #3 is eating oil some. i have listened to all the injectors and they are all working correctly, i have tested the coolant temp sensor and it was within design specs, and no rat nest in the airbox since it is cold air intake and has no airbox. lol

 

hey timber steal,

i found this old post and am looking for some info. I’m looking for your post about reading 02 sensors if you can send a link my way.

I’ve got a 92 460 efi and I’ve been trying to solve a rich fuel condition.

i recently picked up my f350 460 after it sat for 12 years in someone’s drive way with a blow head gasket. Rebuilt top end and did everything on my way out and i am well aware of the the poor mpg of the 460s but i can’t do anything to break 7.1 mpg no matter what i do. It finally clicked to read the spark plugs and i noticed they all looked like they are running rich.

Ive check the resistance on the temp sensor for the computer and that checked out. The pcv looks good although the gromit barely holds it in so I’m going to grab a new one today. Thermostat opens right at 192. I did all the matinance things i could think of to gain mpg. Front in rear diff, transmission flush, transfer case. Even wrapped the intake with heat shields. I don’t have any fuel in the fpr vacuum line. Timming is set at 13.

Replaced the vacuum harness. Replaced the 02 sensor. I’ve done wires, cap, rotor, and plugs.

i haven’t check the egr due to a lack of knowledge. Last time i checked the codes there was just one for a slipped torque converter but nothing since.

thanks for any help in advance