I'm trying to test the EGR system on my 95 e150 5.0 to determine if it's the cause of my failed emission test, which failed on high NOX.

I read that the EGR valve and EGR flow could be tested by applying vacuum to the EGR valve (bypassing the EGR solenoid and opening the valve), which would make the engine run lean by adding exhaust gas and cause it to stumble or run rough.

When tested, I did't hear any change in the idle. The EGR valve is new, but I bench tested it anyway and it's working. This led me to think there was a blockage in the EGR tube, but that was clean.

There was quite a bit of build-up where the EGR valve connects to the intake, and I cleared and cleaned as much of that as I could from the outside.

I retested, but got the same thing.

I'm I doing this test right? Does this mean my blockage is inside the intake?

Any suggestions would be great.

Thanks, v.

 

If you are sure the EGR valve is opening when you apply vacuum, it's a good bet the passages are blocked with carbon and will need to be cleaned further.

 

I was able to confirm that the blockage is in the intake manifold.

The following test was suggested to me on another forum:

..."Easy way to check. Remove the EGR valve and start the engine. If it runs just fine your intake passage is plugged If it has a massive vacuum leak it's ok."

Guess I will be removing the intake.

Thanks.