I have a Automatic 4.9 2wd seems to be missing during normal acceleration and at any constant cruising speed Also engine runs rough and dies when initially started, does this once or twice then idles fine. went on a long 2,500 mile trip and was getting 12-13 miles per gallon. Replaced plugs, wires, cap, rotor, fuel filter, airfilter, oil change, oil filter, and ran 2 cans of seafoam through it and still hasnt fixed my problem.No warning lights. I unplugged EGR to see if that would help (something a buddy told me to try), no change, except check engine light came on, goes back out when plugged back in. I hope someone has experienced a similar situation and can give me some advice.
Thanks

 

Also would like to add the truck has 63,000 original miles.
I pulled the codes.

Code: 327 DPfE or EVP circuit below minimum voltages of .2 volts
556 fuel pump circuit failure

Can someone put these terms into english for me please

 

hey, I just picked up a 93 4.9 with 61,000 miles too.

Sounds like you are having a fuel related problem. Possibly fuel pump not getting full voltage? Sounds like you need to check fuel pressure. Do you have dual gas tanks? If so is problem same in both tanks?

 

Sounds like it's running rich as heck, and I wouldn't be surprised if you have a clogged cat by now.

 

it has dual tanks but I only use the front tank because the rear tank leaks into the front if i am using rear tank. can anyone tell me how to perform a test to check fuel pump circuit.

 

Those codes are for the valves which control the EGR, you may have set those codes when you unplugged it. Clear them and re-test. If the codes re-appear then you are on the track to solving things.

If the rear tank leaks into the front, the shuttle valve in the front tank Fuel Delivery Module is shot.

The bad news is that you have to replace the FDM, the valve is not available separately.

 

i think your right . i cleared the codes and not with the EGR plugged in I dont get any codes. still looking for my problem

 

I also ran the back tank today and still doing the same thing