Sorry about the bad photo, crappy light...
It is an EGR valve
I have a theory, it may not be barking up the wrong tree, but I am throwing it out there.
This week I replaced an EGR valve off a GM 3100, the car was showing Code P1404 Closed EGR Performance, which in my experience means that the pintail and seat in the EGR valve is blocked by carbon deposits and can not properly seal. Looking at the datastream from my scan tool supported my diagnosis. I pulled the EGR valve and it did "look" bad. I did not test with a scope or DVOM at the connector. Reset the computer, problem hopefully solved.
As I was test-driving the car, I noticed a remote starter key fob. I started to think, if a vehicle is idling for a long period of time, chances are that the EGR valve will be closed, or only pulsed very, very briefly. The EGR valve does not becomes really active until the vehicle is accelerating, decelerating or under load. While the car is warming up at idle via the remote starter, the exhaust gases are colder and contain more unburned fuel. These are prime conditions for forming carbon deposits, and these conditions last longer because long idle cycles only extend the time the EGR valve is subjected to these conditions.
This is just my theory, I must do more research before I destroy the reputation of remote starters.
What do you think?
5 comments:
There is a test of the operation of the EGR for each key cycle. There is a time out for the test. If I remember correctly. the test is after the vehicle is placed in gear and there is a vss signal. I will see if I can find the engineering data.
I read some ways on how to check the GM EGR valves: 1. Simply unplug it, cap off the vacuum line and drive the vehicle. If the problem goes away, you have a problem with the EGR control system.
2. Connect a hand vacuum pump to the EGR valve and slowly apply vacuum to it. If the engine rpm slows down and stumble and probably stall when you get to full vacuum.
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