Hi guys on 12/29/2010 I wreck my 1996 F150 Eddie Bauer 5.0 and The Insurance Company Totaled out my Eddie Bauer. I bought a another 1996 F150 XLT 5.8 and it was setting up for awhile. The Check Engine Light is on The codes are PO401. Definition The EGR System fault (exhaust gas recirculation) Explanation The ECM has detected too little flow on the EGR system probable cause 1. bocked passage on EGR system 2.Failed EGR valve 3. ERG solenoid faulty 4. failed EGR pressure sensor where applicable 5. Failed EGR position sensor where applicable PO171. Definition fuel trim bank one condition explanation the powertrain control nodule uses the oxygen sensor to calculate the air / fuel ratio of the engine. The computer has recognized a rich or lean condition on one engine bank only. probable cause 1. if bank one and two codes set together suspect fuel pressure or naf (mass air flow) sensor 2. Oxygen Sensor defective 3. Ignition misfire - repair 4. Fuel injector problem. When i drive the Truck Slow sometimes it heistates. I know the EGR Valve is good. When the Truck is running and i turn the AC on i Here heissing from the AC panel on the Dash The EGR Valve does not have no Vaccum on it when the truck is running. Can any body help me out on what to do to get rid of the check engine light off. I got A good deal on it and i like it.

 

It sounds like you have a vacuum leak. I would have a local shop smoke test the vacuum system to find the leak. That doesn't cost all that much to have done.

 

I found it easier to test each vacuum circuit myself. I had invested in one of these several years ago:



Harbor Freight MityVac Vacuum Pump

It is very useful for finding vacuum leaks, bleeding brakes, testing vacuum sensors, etc. One of the handiest tools in my toolbox IMHO.

 

Good suggestion. I have a vacuum pump too and it is very nice to have. I have found though that some parts of the vacuum system are hard to check this way because they are not always closed.

 

How would I go about testing the vacuum system with the tool you are talking about?
Thanks for the reply.

 

I've used a small propane torch works well to locate leaks, no flame of-course but less risky than flammable liquids and less chance of electrical damage. Extremely small leaks are a little more difficult but good luck.

 

I disconnect each vacuum circuit from the manifold, then pull a vacuum on it with my pump/gauge. If is does not hold a vacuum then I start tracing down the tubing. I found most of the vinyl/plastic tubing to be very brittle. Most of it broke when I touched it. I replaced all of it. From there I found a leaky vacuum reservoir for the HVAC system and another metal reservoir hidden behind the driver side headlight was rusted out.

Those pesky plastic vacuum lines tend to have dozens of small holes along the length of them. No amount of carb.cleaner that I sprayed showed me much of anything. Once I pulled out my trusty vacuum pump/gauge I found the real story.

The one exception of where I was fooled is the EGR circuit. I found out the EVR is a controlled vacuum leak. It is normal for it to not hold a vacuum. At least I found that to be the case with the old and a new EVR. The EGR valve itself should hold a vacuum. The EVR, not so much.