I'll add this thought for what this may be worth to you. I had very similar engine symtoms and a 41 code that drove me nuts for months. I replaced all the sensors and the FPR and everything else imaginable with no success. It finally turned out to be fuel injectors (it may have been just one injector but I replaced all eight to be safe). What clued in a more seasoned mechanic than I was that when carb cleaner was sprayed into the throttle body the idle would smooth out perfectly. The carb cleaner was having the effect of adding more fuel. Secondly, with the proper test equipment, I could see the O2 sensor start switching when the carb cleaner was introduced. The O2 sensor would always read lean (code 41) at idle before. It was quite a jump for me to replace the injectors but it did the trick and the lean code was history.

Make sure there are no vacuum leaks.Verify that the fuel pressure is correct and then try spraying carb cleaning in the throttle body. See if it smooths out the idle. It might help you narrow down the possibilities.

 

Jemini
good post
Frank

 

YOu should also check the fuel pressure regulator. If it is running too high it could be dumping too much fuel through the injectors. when the engine is cold it would not affect it as much as when the computer thinks that is warmed up.

 

if you find out let me know i have a 93 5.0 2 wheel drive thats the same changed map sensor cap rotor plugs wires and coil ran great 4 about 100 miles and started again seems to be runnin real rich im boggled

 

Jemini: Excellent consideration. I just bought a proper fuel pressure tester and hopefully today will find time to test the entire system, including the regulator. I'll add your suggestion. Found a junkyard to sell me a MAP for $25 from a truck that rolled, so I expect it'll be good, I will also try that if the fuel tests come up nada. At that price, I can have a spare MAP if that ain't the problem.

 

I had the same symptoms on my 93 302 4x4 and replaced the TPS and all was good again. Didn't check codes just took a $35 educated guess.

 

RE-edit:
I put the new gauge on the fuel rail and turned the key to get the fuel pump to go on. pressurized right up to 40 lbs. Started the engine and it stayed there for about 5 seconds then zoomed up to 80 lbs. A major clue.

The book says it might be a blocked return line, bad diaphragm, or bad vacuum. Assuming my earlier vacuum reading of 20 inches and steady was correct, that leaves bad FPR or return line. But I can't figure out how to disconnect the return line fitting without mangling it. Mine is different than the one shown on fordfuelinjection.com. http://www.fordfuelinjection.com/index.php?p=41 .


It looks like a braided line going up to some kind of stainless fitting and tube with a safety clip holding the line and fitting together. The clip is easily removed, but the stainless fitting looks formidable. Does it press in/out? Does it take another frigging special tool?

 

Well, I answered that question, it's a "spring lock coupling" and takes a $10 tool, if they got it right.

I may just pick up an FPR and throw the FPR at the damn thing.

 

Now we're getting somewhere (hopefully). If the vacuum is correct, it's the FPR or the return line. You can test the fuel return without having to disconnect the actual line by removing the FPR and using a bike pump and a tapered nozzle. Insert the nozzle into the return line where the FPR would normally connect. Be sure to get a good seal (a bit of teflon tape around the nozzle will help). Pump the handle a few time and see if it builds any pressure. If it does, the line has is plugged. For what it's worth, I've never actually seen a plugged return line though I'm sure it does happen. If it is plugged, I'd bet it's the result of kink or bend in the line rather than debris. If this doesn't help you determine it one way or the other, put the FPR back on and disconnect the return line at the FPR. Hook a piece of hose to it and direct that into a jar/bottle then start her up. If it runs fine, it's a plugged line. If not, replace the FPR. And yes you'll need another friggin special tool to disconnect the fuel line (it's a Ford what did you expect). Click this link to learn the different fuel line connections (of which all 3 may be found on your truck in one way or another): http://www1.autozone.com/az/cds/en_u...rInfoPages.htm

Was gas present in the vacuum line when you disconnected it? Did you see any when you put the FPR under a vacuum? If so, the FPR needs to be replaced as the diaphragm is torn allowing fuel into the vacuum. It also could be a failed spring or stuck diaphragm (rather than torn) which would allow you to build and hold vacuum at the connect.

 

re: injectors

They're not that hard really. You'll have to disconnect all electrical connections, throttle linkages and hoses/lines and remove the upper intake manifold (which will require a new gasket kit - $10). Be sure to label everything as you disconnect it as it make assembly much easier. Then remove the fuel rail and disconnect the wiring at each injector. You then pull the injector out using a rocking motion. Inspect and clean. Replace the o-ring (lubricate new ring with clean engine oil). Replace using the same rocking motion. Replace the wiring, fuel rail and manifold. Reconnect everything.

 

About that fuel rail spring lock coupling, I got a plastic version of the tool from Sears. Worked, but was difficult. I was looking for the long handled metal version, but could not find it. Last weekend, I was at Harbor Freight, and saw the metal one there.
Be patient when you are doing this. Some guys have had real hard time getting it to release. I used PB Blaster and compressed air to try and clean the coupling really good. Once the spring releases, it comes apart easy. Going back together is as quick as plugging in an electric plug.
I read quite a bit about rebuilding and cleaning injectors before I did mine. It is such a chore to get to the injectors, I did not want to have to do it again, so I bough a set of rebuilt ones off Ebay. A guy in Wa, runs an Ebay business in rebuilding and cleaning, and flow testing injectors. They were about $10 each delivered for my 300. After I pulled my injectors and saw how dirty they were and 1/2 of them had cracked pintle caps, I just pitched them. I can find his name if you want to go that way. He is set up for buy it now, and ships pretty quickly. My truck didn't run bad before the injector replacement, but it definitly ran better after.
Good luck Frank

 

+1 on the injectors...while not hard, it is time consuming. Will require several hours to complete.

Frank - PM the ebay guy. I've been wanting to pull my injectors and clean them but may just replace if some are available inexpensively. Like you said, it's not running bad, but could be running better. Thanks. Raymond

 

http://stores.ebay.com/Mr-Injector

My memory was faulty. Prolly from low voltage . He is from Idaho not Wa., and the injectors are closer to $12 each. He has 1843 feedbacks at 100% positive.
Frank

 

The fuel pressure regulator! I decided to throw one in instead of testing the return line and all, and got lucky.

A bit of a pain and another $65 or so, but we're back in action! Thanks to all the guys with suggestions and for hanging in there with me. I think I've repped you all, but I would like anyone reading this thread to give rep (the little scales next to the post # )to them too. It's really what the rep points should be for on FTE .

I should really knock on wood here...I'm gonna fill the tanks... or maybe just one of them at these prices, and see what my mileage is like. I'll report back in a couple days before I end this thread.

 

Hell yeah...glad to hear it!! I wish I would have thought of this earlier. Frank saved it for you...I've left him rep points.