Hello everyone. I have an 89 IROC with a 5.7 TPI. I have been having a problem passing emissions for NOx in Massachusetts. I only drive the car in the summers and I failed test number 1 with a NOx reading a 4.6 grams per mile. I them replaced the EGR vacuum solenoid, dumped 6, 12 oz. bottles of methanol in the tank, with 93 octane fuel and got a reading 3.5 grams per mile on the retest. So I failed by a half a gram per mile. Here is the test results in full:

Test 1

Result Limit
HC Grams Per Mile 1.41 2.00

CO " " " 10.52 30.00

NOx " " " 4.61 3.00



Test 2 Result Limit

HC Grams Per Mile 1.22 2.00

CO " " " 07.17 30.00

NOx " " " 3.52 3.00


With my research on the forums I tested the EGR valve by applying 10" of vacuum to the EGR valve itself with the key off, car off. It held vacuum. Then I then started the car and the vacuum went to zero, with, through my research, I assumed that this meant that the EGR valve was opening and closing freely, and functioning properly. The valve could not be tested with a vaccum pump while the car was running becasue it has a bleed off. I then proceeded to test the EGR vacuum solenoid, with it energized in diagnostic mode I then connected the vacuum pump to the manifold side of the solenoid valve. I then applied about 10" of vacuum, and as I understood it, if functioning properly it should hold vacuum, which it did not. I concluded that the EGR valve was functioning properly, and the EGR vacuum solenoid was faulty. But now I am not so sure since I still failed my retest. I do have full manifold vacuum going to the EGR solenoid from the throttle body, and since I replaced the EGR solenoid, I also have vacuum going too the EGR valve itself, from the solenoid. So my question this. Did I test the EGR components correctly? Could it be carbon build up? Should I have used more methanol in the gas tank, or another additive to help lower NOx? Is there anything else I should check or try to remedy the situation? I should mention that the car is in extremely good condition, freshly tuned up with only 80,000 miles on it. It runs perfectly with no trouble codes, stored in the ECM or other wise. I do have a hypertech cool fan switch, thermostat, thermomaster chip, borla exhaust, edelbrock headers, and catco cat. This is the first year I have had a problem passing emissions with this car and these components. I did removed the thermomaster chip before inspection. If anybody has any comments or suggestions they would be extremely appreciated and helpful. Thanks