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1994 Plymouth Acclaim 3.0 Failed Smog Test

My Plymouth Acclaim failed all three sections of the smog test. Visual and fuctional failed (PCV) due to breather hose had come loose near where the air filter and power steering pump are and Fuel cap wouldnt pressurize due to cracks on the inside of the cap. After this gas cap was replaced, breather hose was reconnected. PCV valve was replaced along with hose going from it to the Valve cover. Is this enough to make it pass upon retest?

Looked on your list for failures of NO readings. Cat and 02 sensor were replaced four years ago (cause of failed test in 2009). Could one or both of these gone bad in four years? Or could it be something else?

All gaskets and seals were replaced in engine in March 2012. At that time Timing belt, plugs were replaced. Check engine light is not on. Vehicle has 192,000 miles on it.

Emission test results:

15MPH: RPM:1659; %CO2: 14.6; %O2: 0.2; HC: Max 61 measured 61; CO: Max 0.36 Measured 0.20; NO: Max 493 Measured 363.

25MPH: RPM:1540; %CO2: 14.6; %O2: 0.4; HC:Max 37 measured 20; CO: Max 0.35 Measured 0.00; NO: Max 516 Measured 747.

Answer:

NOx emissions are normally due to defective EGR valves and/or systems. High compression, high engine temperatures, and/or vacuum leaks may cause high NOx also. If after all emissions systems are inspected and no faults found, consideration should be given to the CAT. Having fixed the PCV problem might allow NOx to return to normal values however this can not be guaranteed until a second smog test is obtained with the PCV hose connected. NOx normally being caused due to defective EGR systems, we recommend inspecting the EGR system prior to a second smog check (assuming your Plymouth Acclaim is equipped with one). According the the Mitchell Emissions Application Guide, the automatic transmission version of your vehicle is equipped with an EGR valve and the standard transmission version is not. Your Plymouth's EGR valve should be inspected to ensure its proper operation. A working EGR valve should be able to open its passage using manifold vacuum. Manifold vacuum is created during the engine's intake cycle. The high demand for air during this cycle creates a vacuum within the engine's intake manifold. EGR systems are prone to collecting carbon build-up. Since the EGR valve pulls exhaust gasses from your exhaust and introduces them back into your engine's intake air over time it will become clogged or stuck open/closed from the carbon deposits. It is possible to clean the EGR valve if you remove it from your vehicle and either spray it out with a parts cleaner. Also ensure the EGR passages on the intake and exhaust manifolds are clean. posted by SmogTips Support

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