pcv valve trouble..at wits end

[gpz2]

I have a 96 metro 1.0L. I have read all of the posts on this site concerning EGR operation, and all other sources on the internet and cannot fix the problem. It is tripping the code for low egr flow. The first time I took the egr valve off, it was full of carbon, I have cleaned it. By bypassing the modulator I can verify that vacuum will activate the valve. I have checked voltage at the solenoids that regulate vacuum to the modulator. The voltage to the solenoids is very erratic and never goes above 3.5 to 4 volts. I have checked the IAT sensor and engine temp sensor. I reset the code after each attempt. It continues to throw the code. The engine burns about a quart of oil every 1000 miles. Could a coated O2 sensor be the cause? How does the ECM determine "low EGR flow"? Any suggestions are appreciated.

[Senatorfan]

I had the same problem with my 1994 Firefly : I changed the modulator, vacuum selenoid switch, cleaned the egr and the throttle body ports but the code kept coming back.

Here's something you could try first since it will cost less than $3.

I simply replaced all the vacuum hoses even though they seemed to be fine and guess what, the check engine light disapeared! There must have been a leak.

[gpz2]

I messed up on my subject post. It should have said EGR valve. But yes, I have replaced the vacuum hoses also. It still trips the code.

[tude123]

Yes, I had the same issues as you described. And for me, the problem was the exhaust port that runs from the exhaust manifold to the EGR valve was clogged with carbon. This port is built into the engine block and also passes through a portion of the intake manifold (if I'm remembering right). Believe it or not the MAP sensor is what determines that the port is clogged. The processor periodically sends the EGR valve a full closed command and it requires a coresponding pressure change from the MAP, and if it doesn't see the change it faults out on EGR.

To check to see if your EGR ports are plugged, simply remove your EGR valve and try to force compressed air in both directions. One port should pass air to the exhaust manifold and the other port should pass air to the intake manifold. I hope I didn't ramble on too long with this idea but it took a lot of research (and time) to solve this problem in my car and I hope I can save you from the hassle.