check engine is on, got code stating egr valve overflow. replaced valve, reset code and light is still on help

Question

after replacing egr valve as stated before and resetting code engine light will stay off for about two days then come back on any suggestions

have 97 isuzu trooper with 87k miles on it

took car to autozone for code. code was e-401

updated code is not e-401 it is p-401 instead hope this helps

Answer 1

OK, first off, ignore the post about the blinking light
When the light blinks, its a "Catalyst-damaging" misfire, and yes, its more serious than just having a light on.
But to the point, the light only comes on when the computer calculates that, due to some type of failure, the emissions are exceeding 1 and 1/2 times the amount allowed by law at the time of manufacture. So , IE-if the lights on, emissions are up and mileage is usually down-bottom line.
Now to the long-winded post from the 20 year mechanic-he didn't realize that your vehicle doesn't have a vacuum -operated egr-it has a linear egr valve that GM developed and has sold the license to.
What you didn't' actually state, but is very important , is just what code is present when the light comes on-is it the same code as originally scanned, or a different one that still pertains to the EGR system.
The valve is operated electrically, and there are several posts in the tech websites for EGR problems-the most prevalent being the position sensor integral to the valve goes out, causing "insufficient" or "excessive" egr codes
' Also, there are problems with the EGR passages in the intake manifold clogging up, causing the light.
Just exactly which code comes back, please, and I'll try to help more.
And to really throw a monkey wrench into the equaton, these valves are very suseptible to pieces of carbon breaking loose from the egr passages and hanging them open-just pop the valve off, and see if the movable pintle is being held open. Also, push the pintle open and, holding the valve upside down, shake it out-sometimes just the act of removing the valve will dislodge the offending piece of carbon. and it will stick again the next time its opened by the computer. If there's a piece of carbon holding it open, then usually the intake and heads need cleaned-you can pour A LITTLE bit of Chevron's techron into the EGR ports while the valve's out -
into the one with the blackest interior.
Good luck

Answer 2

Are you sure the code number is the same? General Motor EGR steper motor has a pintel that closes off the egr port. If that port has carbon build up scrape it out clean with a pocket knife or one out of the silverware drawer "wifes like that" That can be causing the valve not to fully extend closed sending the wrong signal to the engine control. And then light the engine light. Most the time a small egr leak causes rough idle too.

Answer 3

In order for the Egr valve to work it needs to have vacuum. Get a length of vacuum hose and run it from any vacuum source,such as the Pcv valve and connect it to your egr valve while the car is running. The car should start to run really bad ans stumble. That means the egr valve is working. Trace the vacuum hose from where it connects to the egr valve to what ever it connects to. I can't remember what it's called. But it should have like 2 to 3 vacuum hoses going to it, and An electrical plug. That part is probably bad. Or the part that is mounted to your engine that has a vacuum hose going to the Egr valve tube. Thats the metal tube that is connected to your Egr valve. It runs to your exhaust system. I wish I could remember the names of these parts but they are just letters. Like eppv valve or depv or something like that. If you replace those parts I believe you can reset your computer codes and the check engine light should stay off from then on.

Answer 4

Hi You can take it off and clean out the carbon. The egr valve keeps the combustion chamber under 2500f. Otherwise the valves get burnt, head gaskets blow etc.

Answer 5

I was once told by my Lexus mechanic, if the light is not blinking off and on...there is no reason for alarm.