1997 ford f150 just had egr valve replaced.. engine is hesitant and check engine light is on with error code 401.. whats the prob?

you have to ck the engine with a obd2 tester and find out what the codes are , I believe the intake is prob getting carbon in it and starting to clog egr which stops vacuum which will make it run lousy po 401 I think it will read ,, why did you change these parts , always ck with a scanner , do not just change parts and throw your money away ,

Normally a shop would use a scanner to watch the operation of the EGR valve and sensor.
Code 401 means the sensor is telling the computer the flow is not enough. So the problem could be the sensor rather than the EGR valve. And yes one of the ports could be blocked too.

sounds like either a vacuum leak (check the bottom of the "tomatoe juice can" for starters) or a bad or plugged egr valve or egr solenoid.
check engine lite refers to emissions probs only...most likely egr or vac leak. Had the same prob on my 95 5.0 f150...needed new can and egr valve.

Check your Idle air control valve or EGR valve, unplug egr valve and if it idles down and smooths out then replace it, if nothing changes I would consider replacing the IAC.

P0401-Insuffcient EGR Flow, this is caused by clogged EGR ports or a bad DPFE sensor. Is this the 4.6L ? go to my profile page and look at my tips for P0401, try those tips and see if that corrects your light. Hope that helps.

there's a solenoid under the intake manifold which has vacuum hose connects to egr valve. this solenoid is having a lot of problem.

The EGR and the lift sensor may look perfect from the outside but the under side of the EGR valve and the EGR passage (small tube) are the REAL WORKING parts.

The carbon inside the EGR passage tube and the underside of the EGR valve must to clean out.

Make sure you has a NEW EGR gasket before you start the job.

It's a 2-3 hours job.

If you do not clean the EGR passage tube the Nox emission will get higher (check you past emission reports).

It is very possiable that you may be getting a false code that will reocure till egr problems are repaired. The ecu may be trying to compensate for egr problems causing it to send the 607 code

check inside the egr port on the intake for carbon build up.if so clean it out with a piece clothes wire.then vacuum up debri with shop vac.

This is an airflow problem. Usually thought to be a EGR valve problem but the problem is the sensor not the valve. With OBD 2 you should have a DPFE sensor. (Delta Pressure Feedback EGR) that is a silver box with 2 hoses coming off the bottom that connect to the egr tube. That is the problem. Replace the sensor and your P0401 (that is the correct way to write the code as the P stands for Powertrain) will go away. The new updated DPFE sensor will be plastic and will probably require an updated connector. The connector should come with the updated sensor. And please use Ford Sensors.
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