I used a friends snap on scanner to scan my truck and these are the codes i came up with. Can someone direct me on what to fix to correct my rich runny problem. I drove 30 miles today and used over a 1/4 tank.

539-a/c or defrost on- no big deal.
626 coast clutch solenoid (ccs) what the heck is that?
171 no ego switch at adapt limit-bank one
173 ego not switching,rich exh bank one
179 cruise lean limit, bank one still rich
327 egr signal too low
328 egr (evp) votage below closed limit.

what should i change first in order to at least get a little better milage out of this pig. thanks.

 

626 -- E40D coast clutch. Part of the auto trans control that ensures engine braking in 3rd gear, among other things

171, 173, 179 -- The engine is running rich. The computer is trying to lean it out. It is failing in this endeavor. The oxygen sensor is indicating rich and refuses to switch, despite the computer pulling out the injector pulse width all the way to the adaptive limit. Check your fuel pressure. If it is way too high, it will run rich. Check for the possibility of a failed fuel pressure by pulling the vacuum line off it -- if there is gasoline present there, the regulator is bad and the engine will run rich.

327, 328 -- The EVP sensor may be bad, or the wiring disconnected. If the EGR valve is stuck open it is possible for the excess exhaust gas to displace enough air to cause rich running. This is fairly unlikely, though, as your idle quality would be pretty bad and you didn't mention that.

You could try a KOER test to see if it also comes up with code 173. This makes for a controlled environment to try to track the rich running down.

 

Thanks for the added info. As far as idling i did forget to mention that. if it has sat for more than about 5 mins when you start it the engine idles at about 1000 rpm for about 45 secs to a min. or until you tap the gas to increase rpms then it will idle at about 6 to 800 or so. also at an idle it will surge about 100 to 200 rpms in idle speed. where is the ccs? is it replacable? if so where can i get one. and about the evp is that available from like napa or autozone or is that a dealer thing? one more question, what should the fuel pressure be? should i check it with key on or running or both? I have pulled the vacuum line off the top of the fpr and didn't see or smell any gas.

 

The coast clutch solenoid is part of the solenoid pack inside the transmission. The solenoid pack can be replaced or repaired after dropping the trans pan. The problem may be in the wiring or connectors, not the solenoid. The symptoms would include a lack of engine braking when coasting with O/D locked out. This does not explain bad gas mileage. If the solenoid pack is bad, it is a Ford only part.

The EVP may be available at autozone or the like. Try www.autozone.com or napaparts.com, etc. If you strike out there is always fordpartscheap.com.
It is just a rheostat like the TPS.

Check the fuel pressure with the key on but engine not running. Should be 50 to 60 PSI on an I6, 38 to 48 PSI on a V8. Start the engine. The pressure should drop about 8 PSI at idle. This is from memory. You can look up more accurate pressure specs for yourself.

You are really looking for truly ridiculous pressures like 90 PSI if this is the cause of your too rich running.

The idle behaviour you cite is more-or-less normal. The computer controls the idle speed in response to load, such as the A/C or alternator or power steering pump etc. It also implements a "fast idle" strategy for cold warm-up and a dashpot effect for coasting to a stop. A 200 RPM surge is a little high, you could try cleaning the IAC.

 

one more question!! since I am out of town and can't work on the truck right now it is bothering me thinkin about it and not gettting answers. If i replace the evp that should take care of the rich running problem. now if it doesn't and i check the fuel pressure and it is really high like 75 80 or even 90 should just a fuel pressure regualtor fix the problem. my fuel pumps are whining like crazy that is y i am wondering.

 

I replaced the fuel pressure regulator friday and that seems to have fixed it. I can't smell a really rich exhaust anymore and i drove 80 miles to work today without getting a check engine light. and my mileage has improved. looking in the old fpr i think dirt got in it and stuck it open. i didn't check the actual pressure but the pumps stopped whining and all seems well. KNOCK ON WOOD!!!!!!!!