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1989 Dodge Dakota High NOx Problem

I own a 1989 Dodge Dakota pickup truck. It has failed the smog test 3 times for the same problem. I have a High NOx reading 1075 ppm (750 is max) . Everything else is within the emission limits.

I have change the sparks plugs, put in a new EGR valve, air cleaner and have had the truck good and warmed up before the test was ran. I was told that I am not getting any vaccum from the EGR valve. I have vaccum up to the valve itself. But the valve is not doing anything. I have even cleaned out the EGR ports on the engine manifold. Truck run very good, even without a working EGR . Is the manifold blocked ? What else should I do ? Engine has about 110,000 miles on it and runs very good. Need to pass the Calif. smog test. Help

1989 Dodge Dakota - California Truck

Answer:

We have to believe the EGR ports on the manifold are blocked, assuming the EGR valve is functioning properly (opening off idle). You might want to run your Dodge Dakota's engine with the EGR disconnected, and add propane to the intake port to watch for a rise in idle. Be absolutely carefully doing this; this test procedure is recommend only for advanced automotive mechanics. Should you see no increase in engine idle with the addition of propane you can be certain the EGR intake port is blocked. You will need fine tools to enter the port and clean out carbon deposits. If you do notice your Dodge Dakota's engine idle increases with the addition of propane, check to see there is exhaust coming out of exhaust manifold's EGR port. A plugged EGR exhaust port is not as common of a plugged up EGR manifold port. posted by SmogTips Support

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