Help. Check engine: P0401 **FIXED**

[Squisher]

'98 F150 4X4, 4.6L with 122K mi.

Check engine comes on after vehicle is fully warmed up, may go out, may not. Autozone hooked it up and:

P0401: The ECM has detected too little flow on the EGR system

Probable causes:
Blocked passage on EGR system
Failed EGR valve
EGR solenoid faulty
Failed EGR pressure sensor (where applicable)
Failed EGR position sensor (where applicable)

I hooked up my vacuum pump/tester to the EGR it seemed to be holding pressure. So, I figured it was the pressure sensor, bought a new, still FUBAR.

I took the EGR off today. I stuck a wire down the tube coming from the exhaust and it seemed to just have surface carbon in it although I didn't get far down the tube. Played some more with my vacuum tester on the EGR and it seems to be functioning. It would lose vacuum very very slowly which could be accounted for with leakage around the hose. I squirted some gumout on the valve and blew it out with a nozzle.

Check Engine still came on after about 5-6 miles of driving. Help!


EDIT: fixed it today. Both EGR ports going into the throttle body riser/spacer/elbow were totally plugged shut. I pounded a piece of .150" aluminum wire into the shape of scoop and dug a ton of stuff out of there. The truck seemed to be running smoother. I might actually check the mileage I'm getting now that I won't be depressed by the results.

I think this was the first throttle body I've ever taken apart. Talk about easy. Apart from one EGR bolt that picked up a thread everything went smooth. Much easier than NA.

Next up: One light in the instrument cluster, front and rear diff. lube change, and the biggy - a slow leak in the transfer case.

 

[Zenmervolt]

The valve is supposed to open at certain points. Just because it holds vacuum doesn't mean it's good. It's also possible that there is a blockage somewhere in the system as well.

ZV

 

[LTC8K6]

Is the solenoid working?

 

[Squisher]

Originally posted by: LTC8K6
Is the solenoid working?

Haven't checked it, I was just looking through my shop manuals for a means to check it.

btw-Ford Factory Manuals leave a little to be desired.

 

[Squisher]

Originally posted by: Zenmervolt
The valve is supposed to open at certain points. Just because it holds vacuum doesn't mean it's good. It's also possible that there is a blockage somewhere in the system as well.

ZV

After I posted, I did some nosing around the F150 forums and just about everybody says it is the EGR ports which require the removal of the throttle body and some sort of riser to clean. They also say this will do good things for gas mileage.

 

[bobdole369]

I did something similar on my 89 firebird - removed the EGR port on the intake, and scrubbed a metric load of carbon out of there. Not too hard I bet ford has a way to do it too.

 

[alpineranger]

The way many engine computers decide whether to set that code is by actuating the egr valve and seeing how the manifold vacuum changes. So yes, some restriction either in the intake port or the passage leading from the exhaust manifold to the valve itself will cause this error.

 

[Squisher]

Fixed it today. Both EGR ports going into the throttle body riser/spacer/elbow were totally plugged shut. I pounded a piece of .150" aluminum wire into the shape of scoop and dug a ton of stuff out of there. The truck seemed to be running smoother. I might actually check the mileage I'm getting now that I won't be depressed by the results.

I think this was the first throttle body I've ever taken apart. Talk about easy. Apart from one EGR bolt that picked up a thread everything went smooth. Much easier than NA.

Next up: One light in the instrument cluster, front and rear diff. lube change, and the biggy - a slow leak in the transfer case.