I have a Chevy Silverado 2500 5.7L V8. I have been having problems with passing smog. First one failed because it needed a new cat. Replaced it and tested again. NOx emissions are off the chart (1450/1006 max of 992/59615/25mph). I replaced the EGR valve based on a suggestion. Quick test today said the NOx emissions are still way off. Suggested that I change the EGR solenoid valve and also pull the EGR valve and use a coat hanger to clean some of the carbon build up. I purchased a new solenoid today but looking at it I noticed something. Since there are what are appear to be two ports on one side of the solenoid, I must have replaced the vacuum hose onto the wrong one after replacing the EGR valve. How much would this make a difference on the test readings taken? Would it be beneficial to just replace the solenoid anyway or try to test again with the current one but connected properly?
if the spark plugs are bad the oxygen sensor with sense the exhaust is not hot enough and the computer with allow the injectors to let more gas in thinking that since theres no fire it needs more gas causing it to run like its flooding and exhaust readings will be high. make sure the air filters clean
Need to know the YEAR of your 2500 Silverado! ADDED: Thanks for the additional information, Yes that will cause an issue if the vacuum solenoid is connected wrong, but is very important to pay attention to what EGR valve is being installed (as this vehicle came with 2 different types of EGR valves (the negitive backpressure and the positive backpressure type) Here is how to test it: 1. Check the Exhaust Gas Recirculation (EGR) valve solenoid to have only 2 wires. If it does, the EGR valve is a negative back pressure style valve identified by an N stamped after the number on the valve. 2. With this type of valve, the solenoid is an on/off type and the scan tool control is 0/100%. To check the valve, pump the valve up/open by using a hand vacuum pump with the engine off. Start the engine and the valve should slam closed, and the vacuum on the hand pump should go to 0 inches. The engine should start normal. The EGR valve should not pull open with the engine idling when vacuum is reapplied. An internal bleed will dump off any vacuum applied until a certain amount of exhaust backpressure is applied to the valve. 3. If the valve moves, replace it using an Original Equipment (OE) part using the number on the valve that is calibrated per application. 4. If there are no problems found with the valve, install a vacuum gauge in-line with the solenoid and EGR valve and test drive to monitor the amount of vacuum applied. 5. The valve should have vacuum applied when in gear and off idle. Vehicle speed is needed on some models (manual transmission). ADDED: I don't know if you understand but, If your valve has N (negative) stamped on top and you have a 2 wire EGR vacuum solenoid than everything is correct!
try changing the egr vac solenoid, and the O2 sensor. dad has a 1992, and i replaced the egr valve, the solenoid, all the vac lines, and the O2 sensor to get rid of a missfire, and help mpg. we dont do smog tests here, so it wasnt for a smog reason went from 12mpg to 15 mpg. your supposed to connect the egr to the normally closed port on the solenoid. should be the top port. there is supposed to be a bit of foam glued to the VENT port. check your check engine light codes, you can do it in 5 minutes by jumpering terminals A and B. read more about it online. code 32 is the EGR code, its the most common code on these old trucks
This Site Might Help You. RE: What would happen if the EGR solenoid valve isn't connected properly? I have a Chevy Silverado 2500 5.7L V8. I have been having problems with passing smog. First one failed because it needed a new cat. Replaced it and tested again. NOx emissions are off the chart (1450/1006 max of 992/59615/25mph). I replaced the EGR valve based on a suggestion. Quick test today...
