Egr

[Meshuggah]

After replacing my faulty O2 sensor my check engine light popped on again shortly after, this time giving me this code:

P0401

Apparently my EGR is messed up some how...

Anyone know what to do, or anyone ever have this problem?

[finfinder]

P0401 - EGR insufficient vacuum....Ok. Been there done this. Start with the cheapest thing first. Remove the EGR valve and see if it is carbon buildup clogged. It will be easy to tell. You can clean it with some SeaFoam Deep Creep (about $9).
You can clean the EGR valve and put it back on. A new EGR valve is about $200. The dealer won't clean it cause they would rather just sell you a new one.
You can clear the code by disconnecting the battery for 10 minutes or removing the appropriate fuse ( I forget which one it is). Drive the car for a few days and see if the code comes back before going to the next step.

Next check the Egr modulator. It's only about 25-30 bucks for a new one at autozone even if its bad. You may be able to just blow the dirt off the pad. The vacuum switching valve is on backside of the engine near the firewall. That's your next culprit. It's a Pita to get off. They could have just mounted it on the firewall and you could change it in ten minutes but noooooo. Check the hoses that connect this stuff too. Make sure that there is no leaking from cracks. If your car has high miles (>200k) a clogged EGR is likely. The good news is that your car will definetly run better after you fix the problem in the EGR system. Change the PCV valve too.

[ASG14]

Ok, so what car do you have?

[new echo owner]

His profile indicate that he has a '99 with an I4, which is probably the EGR VSV problem causing P0401.

N.E.O.

[Meshuggah]

Thank you guys very much, the clogging sounds like a very good possibility as my 02 sensor was burning too lean and was caked in black carbon, perhaps this was circulating through the rest of the system? I should be able to have at it on monday and will let you guys know how it went.

Thanks!

[new echo owner]

Do a search, you might find that the VSV on the 5SFE is prone to sticking and cause a P0401 code.

N.E.O.

[finfinder]

Originally Posted by Meshuggah

Thank you guys very much, the clogging sounds like a very good possibility as my 02 sensor was burning too lean and was caked in black carbon, perhaps this was circulating through the rest of the system? I should be able to have at it on monday and will let you guys know how it went.

Thanks!

Its likely that the same black carbon buildup is on the EGR valve or the Vacuum Switching Valve took a dive. After you get it fixed, run some Seafoam through the brake booster line and she'll run like the old days. Look on Youtube for videos of how to do it. Have your plugs checked while you're at it. They may be fouled as well. If you need to change the plugs and the wires too you may be surprised how well she runs.

[Meshuggah]

There are a lot of seafoaming vids on you tube...what exactly is so great about this seafoam?

[finfinder]

Use the search feature on here and read some of the posts. Seafoam cleans nasty buildup from inside of the engine. Intake, gas,oil. It works.