Vibrates at Idle, Help Please!!!

Rick, you could have a vacuum leak. That would account for the symptoms you cite. I'd connect a vacuum gauge and see what that reads. If I remember correctly, you should read somewhere in the neighborhood of atmospheric pressure (14-15 psi).

Also, I'd visually check the vacuum hoses to make sure one isn't disconnected or has an obvious hole. I'd also suspect the IAC, but that's ruled out since you already changed it.

Another cause could be an EGR valve that has stuck open. To check for this, place your finger on the underside of the valve with the engine at normal operating temp (don't burn yourself!). Rev the engine; you should feel the diaphragm move. If you don't, pull the vac hose and verify that vacuum is indeed being provided to the valve. If you have vac, and the diaphragm doesn't move, this is probably your culprit.

Good luck! Kevin from Wenatchee

I've scrutinized over and over looking for a vacuum leak. Even disconnecting hoses to see what happens. Nothing found. As far as PVC, I did the "hold a piece of paper to the end of hose test", and it checked ok.

I have the computer, OBD 2 Browser scan tool. It shows an EGR STUCK test and it tested ok.

Rick from Vancouver, WA

disconnecting

One other thing came to mind. Carbon tends to build up on the inside of the EGR valve. If the diaphragm still opens under vacuum, the valve will test OK. But if there's enough carbon buildup, the valve may not be closing properly.

Before replacing a fuel regulator, which is probably costly (don't know, haven't done it myself), I'd pull the EGR valve and see if there is excessive carbon inside it. You may even be able to see that the valve isn't closing all the way. You can clean the carbon out with some light sandpaper, and reinstall it. You'll need a new gasket, which you can probably buy for cheap at NAPA. Or do what I've done - make one out of a sheet of gasket material, by using the valve as a template. It's easy enough to check this before throwing money around shotgun style.

Let us know what you find out!

Kevin

Yes, but that is just a range. Does it mean that pressure should be 30 psi at idle, and 65 above idle? Or does it mean that any pressure between 30 and 65 psi at any time is considered "good"? And how accurate is the pressure tester? If the pressure was 10 or 15 psi above spec, then yeah - that's a problem. But 1 to 4 psi could indicate a calibration error, which could happen with any piece of test equipment.

You may indeed be correct, but the EGR check is quick, easy and most importantly - cheap. Personally, I'd check all the cheap and easy stuff first.

Thanks for the input. I'm going to take a quick look at the EGR, It's easy enough. But I believe Rob may be right. The pressure should be in spec. I haven't gone after that yet because the regulator is part of the pump in the tank. But get this, I notice a definite difference from when tank is full to tank low. It's lookin more and more like the pump.

Good luck Rick. Glad to help a fellow Washingtonian!