At idle, is there suppose to be any vacuum in the line that goes to the egr valve? I have a 1995 Sunfire with the 2.2ohv, non-electronic egr valve. The egr valve is only connected with a single vacuum line.
The 1995 Sunfire uses a Negative Backpressure EGR valve. That means when manifold vacuum combines with negative exhaust backpressure, the vacuum bleed hole opens and the EGR valve closes. So at idle you will have manifold vacuum and negative exhaust backpressure = closed EGR.
I pulled the line off the egr valve at idle and it had vacuum, so this is normal operation?
Yes it is normal. The EGR is now closed. If you stop the engine and apply vacuum by means of a vacuum pump the EGR will open. The EGR used on the 1995 2.2L engines need vacuum plus exhaust back pressure to open when running. When the engine is stopped the valve inside the EGR that works with exhaust back pressure is no longer activated so with vacuum alone the EGR will open.
One final note. There will be no vacuum at the EGR on a COLD engine until the EGR vacuum solenoid opens. When the engine gets up to operating temperature the solenoid opens and applies vacuum to the EGR.
I tested the egr vacuum line with the engine cold, and had vacuum thorugh the line. Is it possible that the egr vacuum solenoid is faulty? Where is the soleoid located?
Normaly there is a vacuum diagram under the hood on the strut tower. See if you can find it. You can follow the vacuum tube from the EGR to the next component which should be the EGR solenoid valve. I have only got the service manual at hand and they only show the vacuum diagram but not the location of the solenoid. I have a 1998 and a 1999 Cavalier so I don't know where it is located on a 1995.
The solenoid valve should be pretty easy to test. I would measure the voltage at its terminals with the engine cold and then when the engine is hot. I would assume that with no voltage there should be no vacuum unless the valve is leaking. Has your car got any problems such as rough idle or something else?
It has a rough idle when cold, ok when warm. Also when cruising at a higher speed in 5th gear, I get a CEL. Code is dtc55 lean fuel monitor. Fuel pump & filter have been changed, and the cel only comes on when cruising at very light throttle at higher speeds, never when accelerating hard. I am thinking that maybe the egr valve is faulty or it maybe the solenoid since you state that there should be no vacuum at idle when cold.
If EGR is open while engine is cold you will get rough idle. The EGR on the 1995 is more complicated than most with an internal valve system as well that depends on exhaust back pressure.
Normally, the EGR is closed at idle to prevent rough idle, open at part throttle and, closed at full throttle otherwise the engine would lose power. This is when the engine has warmed up to proper operating temperature. An EGR open at the wrong time can cause fuel mixture problems.
The cheapest and best approach would be to check and replace if needed the EGR solenoid valve. That won't cost too much. If the solenoid valve checks out OK I would then replace the EGR valve. As I have said, it is more complicated than most and it's quite possible that the exhaust back pressure valve internal to the EGR is defective.
The manual that I have has a small drawing that seems to show the EGR solenoid valve near the throttle body. Also, if you do buy a new EGR valve just be sure that it is a Negative Back Pressure type.
