Truck has been sitting for about 6 months, drove it to work for a couple days before having it inspected (about 37 mile trip one way. This is the first time its failed since rebuilding it a couple years ago. I went through the FSM checking everything that could effect the HC, timing is spot on with the jumper in place, checked the TPS to make sure it was seeing it was at idle (timing check comfirmed this also), checked the EVAP everything seemed to be functioning. The only thing I found that was cleary bad was the Charcoal Canister, tried using 45 PSI per the fsm to blow through the tank port, and hardly any air came out the bottom port, nothing came out the purge port. Will the bad canister cause such a high HC reading at idle? Plan on doing a oil and air filter change before taking it back in, was thinking about adjusting the valves too, and driving it some more in the mean time, was also thinking of having the Catalytic converter changed, since it rattled some time back.

Might also want to look into the o2 sensor (if you do, buy Denso / NTK!)

1. cat coverter need replacing?

2. get oil change. drive around for half an hour. dont user freeway. use surface streets. get system really hot.

3. those "guarantee pass" fluid add-ons? dont work.

The CO2% being under 14% is normally a good indicator that the cat isn't doing its job. I am not sure if that is your only issue with your HC's being over 1300 at idle. You might test the exhaust before the cat, and if the cat is working at all at idle.

So I've changed the oil, air filter, sparkplugs, adjusted valves. Wires, cap, and rotor are not very old, ran a tank of gas through it, took it back up to test again. Failed again this time they said the idle reading was higher at 1800, so they stopped the test. My new Denso O2 sensor came in today, so I may run it back up there to test tomorrow.

If it fails with the new O2, pull the cat and have them check the pre-cat levels at idle.

If the new O2 sensor is a universal one, keep the wires the same length as the originals, longer/shorter wires can cause issues with the ecu receiving the signal from the sensor.

Tested again and it failed but the O2 sensor dropped the HC readings to 415. They mentioned how all the readings were lower this time, and that the idle test kept failing, I started explaining how it's always passed when they ran it the treadmill vs the idle test. So they ran it again this time on the treadmill so it was under a load. Passed just fine, had a 158 HC reading for the low speed. I think it needs a new Cat and then it would pass the idle test.

>>>*One question? Did you add fresh fuel? Probably since I see at least three tests. HC is just misfire or incomplete combustion.

Note that sitting for six months can allow lighter distillates to bleed off. In cooler climates it's not a really bad problem but even here in Oregon where it's cool and wet we see that sometimes. Winter fuel has Butane of course which evaporates rather readily.

Also alcohol in today's fuels, I don't care what anyone says, Corn does not belong in a fuel tank. Lots of problems with it, one being what is known as phase seperation. Temperature changes can cause the fuel to end up in layers, so adding fuel remixes it.

We had one locally that was doing similar after sitting for nearly a year, it had a miss at idle speeds and a high idle HC reading, and acted very lean to the point of spitting and backfiring at off idle throttle..

Adding fresh fuel and several very hard drives fixed her right up...*EB

Yeah I ran a couple tanks through it, it does still have a miss kinda, but I'm not sure whats causing it, cant tell if its just the cam or a miss.

I remember years ago I failed smog. Did some testing and figured out my O2 sensor went south.Replaced it. Took it back in and failed again...my old O2 sensor was causing the engine to run real rich which in turned basically burned out the CAT. Replaced the CAT and it finally passed...and my gas mileage went up to boot.

The slight "miss" might just be the cam. I have an E.B. cam also and unless the idle is set just right(jumped and in D for my auto) mine would do the same.

I just started my truck up with seven year old gas in it and it ran like a champ...didn't drive it but it still runs like a champ lol.

Don't know if the CAT is your problem but over the years with a few vehicles I had a O2 ruin a CAT. Now I replace O2 sensors when their life expectancy is up...working or not because they always seem to go to heck within a few thousand miles of that expectancy.

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