98 f150 4.6 DTC 1401, 0303, 0401, 0402 problems - Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars

Jasenford89 · 08-05-2011, 13:10

I have 158K miles on my f150 and i just got the motor rebuilt due to the cats being so clogged up it burned every valve in the engine. So KEEP IN MIND THERE ARE NO CATS ON IT. Just a Flowmaster.

The truck is running rough at idle, and a couple times it actually died on me while puling up to a stop light, when getting up tp speed i feel it slowing down for a second then speed back up, gas mileage is around 11 - 12 Average.

I have cleaned the throttle body and a whatever i could clean out of the intake manifold, and MAF sensor, still nothing.

I already tried to change the DPFE but nothing happened, so i took the part back to autozone, and i exchanged it for the EGR Vacuum Solenoid, still not doing anything, Now since i left the New solenoid on, the truck throws the P1401 and P0303 codes.

I'v cleaned the EGR valve numerous times, lines have all been replaced, except the one on the back of the TB. And still nothing..

Could having no CATS cause any of these problems? Im lost

Thanks

**Bert** · 08-05-2011, 17:51

Have you checked for vacuum at the EGR valve at idle? There shouldn't be any. How about the lines from the exhaust to the DPFE? are they clear.

Jasenford89 · 08-05-2011, 18:22

as far as checking vacuum from the egr.. are you talking about the green line that goes on the top of the Valve or vacuum coming from the little nipple on the valve? There was no vacuum at idle for the actual line, but there was before i replaced the EGR Vacuum solenoid.

Ya there clear and brand new

**Bert** · 08-05-2011, 20:34

The EGR valve may be sticking open a little and that will make it stall or run rough.

Jasenford89 · 08-06-2011, 08:26

Would it be stuck if i was still able to put a line on it and suck through the line and the truck stumbles?

**Bert** · 08-06-2011, 11:55

If it sticks open when it's suppose to close.

Jasenford89 · 08-06-2011, 15:48

alright, makes sense.. is there any way to test it, I,v taken it off several times to clean it, if i really had to i guess i could just go buy one real quick and see what happens..

Would this cause the misfire also?...

I swaped the ignition coils to the different sides, nothin, and i also took the spark plug out of the number 3 cyl (Misfire) and swapped it with the number 2 cylinder (good) but still nothin, im going to check the wires in a bit

**Bert** · 08-06-2011, 17:15

You could set a thin piece of metal in the gasket area and run it. It wouldn't cause a misfire. That's a different problem.

Jasenford89 · 08-07-2011, 13:37

ok..

Well i reset the computer and right now its only telling me p0401 and p0303 and the was about a two hundred mile day.

For some reason i never checked the #3 plug wire as far as putting a screwdriver in it and checking for spark and sure enough no spark so im just going to buy a wireset today.

For the P0401 ill just buy the EGR valve and see what happens... Could a vacuum leak cause this code, because i no there is a leak somewhere becuase my air blows through the dash?

Bluegrass · 08-16-2011, 16:17

The 401 code is a low flow test code.
The tract between the exhaust manifold to the outlet of the EGR cannot flow the required amount of exhaust when tested by the computer.
The pipe orfice may be plugged, the EGR is not opening or the ports behind the EGR are plugged with carbon.
Also if the DPFE cannot read the pressure and send it to the computer the code 401 is the result.
Don't take anything apart until you do a simple test.
Apply enough vacuum to the EGR to open it a small amount.
If the egr opens and the ports are open the idle will roughen up. This means the EGR and ports behind it are open and good.
Then you look at the DPFE as being faulty or the vacuum regulator that supplies vacuum to the EGR is not working when commanded to open.
To replace DPFE, use only a Ford part.
The 303 code likely is a faulty coil.
Good luck.