Ok here is the stumper, at least for me that is. I have a 88 E350 based motorhome with a Fuel Injected 460 that has 50K on the vehicle. It has run well up until now. The vehicle will start fine and then it either runs well or intermittently it seems to run very rich. When it is exhibiting the symptoms, you can not get it to rev out and is seems to have a very bad bog and stumbles. If you hold the throttle to the floor it will run rough and slowly loose rpm and then pop back through the intake after the idle drops to around 2k (for obvious reasons I let up on the gas when the popping starts). Run quality suffers from idle up through how ever many rpms that I can get it to turn (probably less than 3500 rpm). When it is acting up and left at idle will sometimes drop rpm until it stalls, other times it will continue to run. If I continue to run it it will sometimes "clean out" and return to running normally (normal idle and it will rev normally) up until it switches back to its problem. I can usually get it to return to normal operation by turning it off and then restarting. It seems to be hitting on all cylinders and the problem either is there or its not, it does not seem to have any middle ground. The best I can tell is that it is running rich, but it does not blow black smoke when running poorly as far as I can tell. So far here is what I have done: Completely drained and replaced fuel with new twice and used a dewatering agent. Replaced fuel filter on the chassis (the one on the drivers frame rail under the cab). Checked the "bowl" that is upstream towards the tank from the filter and found that it does not contain a secondary filter like some. Replaced the fuel pressure regulator and MAP sensor. Checked Timing. There was one battery that was bad and had low voltage so I disconnected it but the primary starting battery is good, fully charged and has 12.5 volts after sitting all night. The plugs have been changed, the cap and rotor appear fine and I believe are relatively new. The check engine light is not on but does work. I have not checked fuel pressure yet because I don't have the gauge. One observation that I have noticed isthe EGR valve does not move much when it is running normally and being reved but with no load but when it is running rough and you floor the pedal the EGR opens all the way (high vacuum condition?) The plug wires are old possibly original Ford Motorcraft but "appear" good and I do not seem to have any arcing that I can see. The driveability problems are such that I can not drive it down the road because it will only accelerate to 5-10 MPH and will not go up a grade. Because of this and where I live the only way to get it to a mechanic is a very expensive tow so I think that I will keep tinkering. Anyway I appreciate any advise from someone with experience above my shade tree ability.

 

Here is what I would do, first pull the codes. If you don`t have a code reader go to fordfuelinjection.com for instructions on how to do it without one.
After you pull the codes pull the vacuum pipe off the EGR valve and plug the end of the pipe and see how it runs then.
Have a look to see if you are getting good exhaust gas flow out of the tailpipe.
Hopefully some of the EFI experts will chime in soon.

 

Unplugging the vacuum at the egr does not change how it runs and there is good exhaust flow. I will check for codes next. However, the check engine light is not illuminated. Will the OBD I computer store codes without turning on the check engine light?

 

I think it will go on and off when it stores a code but have not confirmed this. A lot of the posters on here say it will store codes without the light.
But if you have stored codes in CM the CEL (MIL) may not be on.

"but with no load but when it is running rough and you floor the pedal the EGR opens all the way (high vacuum condition?)"
That is wrong, the EGR should shut when floor the pedal.

The only time the EGR should open is at mid throttle with a warm engine at high way speed.

As Lazy K said you can unscrew the EGR tube and put a coin that fits (I do not remember if I used a 1 cent coin or a dime) and screw the tube back on but not tight enough to distort the seat with the coin in there. It will take the EGR system out of the pitcher.

To read your CM codes or check for other types of codes and to run the self test go to one of these links below:


This is good for the KOEO test:
Ford Fuel Injection How To Run a Self-Test


This one is good for the KOER test:
Ford Fuel Injection KOER Test


Or get a code reader, here is a good one.
The EQUUS #3145
http://i54.photobucket.com/albums/g9...CodeReader.jpg

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I have checked the codes stored in the computer and found a 24 code in the continuous stored back indicating a faulty air temp sensor. I pulled it out and tested it as per my manuals instructions and found it to be working properly. I think that I will change it out anyway. I have just cleared all my codes and am running the vehicle to see if it throws any additional codes. Thanks for all the help, if anyone has any additional ideas please chime in.