hello all, I posted not the other day about an egr valve problem. We are getting code 34 Egr valve stuck open. First does anyone know it this is something that can be fixed by cleaning the valve or not? Now the bigger problem. Now the truck starts but shuts off as soon as the starter kicks out. The truck will not even idle. Is this just a sign that the egr has completely stopped working? Any info would be greatly appreciated...

Thanks
Nick

 

Maybe it's your I.A.C. ( Idle Air Control )

 

I beleive the truck should idle even with the EGR wide open. Clean your IAC with carb cleaner and post results.

As for the EGR system. There are 3 peices, The EGR valve itself, The EVR (egr vacuum regulator) and the EVP (egr valve position sensor) and anyone could cause that code. The computer signals the EVR to open which passes some (about 6inHg of the main vacuum) vacuum to the EGR. The EGR then opens and pushes a little rod on the EVP. The EVP is basically a variable resistor that sends voltage back to the computer to let it know where the EGR is (open or closed).

As you can see, a faulty EVR could cause the EGR to stay open.
You can disconnect the vacuum line at EGR and start her up. You should not have vacuum at that line and the EGR should be closed. If you have vacuum go the the EVR, there should be no voltage across the terminals at idle. If the EVR is passing vacuum at idle w/o voltage then it needs to be cleaned/replaced. You should have about 15-20 inHg on the main vacuum side.

To Test the EVP:
w/ key off, disconnect sensor harness, turn key on and measure the voltage between Vref and Sig rtn on the harness connector, it should read between 4 -6 volts. If it's not check the wiring. this is unlikely but it does happen.
Next turn the key off and connect an ohmeter to the EVP signal and to Vref on the EVP, disconnect vacuum and connect a vacuum pump. As you increase vacuum the reading on the ohmeter should go from around 5500 ohms to 100 ohms @ full vacuum. If the EGR valve doesn't hold vacuum you have a bad EGR valve. If the resistance isn't in the range then the EVP is bad.
If you don't have a vacuum pump just undo the sensor from the housing and push the rod that sticks out the bottom to make sure that the sensor opperates in range. If it does not operate in range then the sensor is bad. other wise your EGR valve itself is bad.The wire colors are
EVP signal == Brown/light green
Vref = brown/white
Sig rtn == grey/red

Whew... hope that helps :-)
Popa Tim

 

If the EGR is stuck fully open, the engine will idle like crap (lopey, like there's a big cam in it), if it idles at all.

 

Thank you all so much for the info. I am on the road right now but hopefully I will get to it on Tuesday. I'll let you al know what happens.


Thanks again,
Nick