Chrysler Repair: emission testing, plymouth voyager, special instruments

Question
i have a 96 plymouth voyager that will not pass the e test because of the hydrocarbons are testing to high while ideling.Why is this  and what can be done to fix this?The van has a 3litre engine.The van was e tested 2.5 years ago and the same thing happened before but we were not told what fixed it and it must pass test in order to drive it.Thanks

Answer
Hi Eric,
Excess hydrocarbons generally result from there being too lean a mixture of fuel/air. But why that is needs to be determined. You may well be able to do a self-diagnostic test that will help identify the reason because up thru the mid 90's the engine controller had a memory which stored fault observations as codes that the owner could readout without special instruments. Give this a try and see if it works, otherwise a readout with a tool is necessary: Begin a readout as follows: Take your ignition key and turn the ignition switch "on-off-on-off-on" and leave it "on". Do this switching quickly so that no more than 5 seconds elapses. Then watch the 'check engine' light to begin to flash, pause, flash, pause, etc. Count the number of flashes before each pause and make a note of them in the order that they come. The last two flash groups will be 5 in each. Repeat the readout until you have the numbers accurately (the same result, two times in a row). Then pair the numbers two at a time in the order they came, to form two-digit numbers, for example the last number will be 55 which is the code for "end of readout". Then write back and tell me the other numbers that came out and I'll see if any of them are related to your problem.
Roland