EGR Issues

[hoboprodigy-]

My '99 is throwing a code 0401 for EGR 'insufficient flow' - accompanied by a pretty rough idle and miss under low and mid range acceleration - to the point where driving the car makes me angry.

First things first, I took apart some of the throttle body and cleaned the EGR port that leads into the surge tank. It was quite a mess, but I'm fairly certain there is no issue there anymore.

The problem persists. What should I replace, the valve or the sensor?

 

[bacernate]

Use a voltmeter and backprobe the return wire on the dpfe sensor,[ should be 3 wires, 1 ground 1 vref 5volt and the other is the one you want], then start the car and apply vacuum directly to the valve. The car should run noticeably worse, watch for a rising voltage from the sensor, if it doesn't change voltage and the car runs like shit the sensor is bad. If the car doesn't run bad you've still got clogged ports somewhere. Should be about .75 to 1 volt with the car not running and the key turned on. As for your running problem sounds like a misfire to me. Coil taking a dump most likely.

 

[rubydist]

Get a store to pull codes for you - a lot of times the misfire will be reported by the pcm, which will help you narrow down if you have a coil issue.

If your egr passage was that full of gunk, then there is a good bet that your secondary butterflys are as well. I'd recommend pulling off the intake and a thorough cleaning.

 

[hoboprodigy-]

The only code I pulled with my tuner was the P0401.

 

[SHOZ123]

On a cold engine start the car and let it idle for a few minutes. See if the EGR valve gets hot. If it does it is leaking gasses as it should be shut at idle.

Because of the missing and stumbling I would suspect this or the EGR vacuum solenoid is leaking if not the actual vacuum line.