Emissions mystery

[millerrl]

Hi everyone.

I'm new to this forum and have read some really good stuff here.

Hopefully someone has had the same problem I'm having and found the solution.

Stats: 1995 Astro, 4.3, 170,000 miles.

Recent maintenance: new brakes, new water pump, new radiator, new high end spark plugs, new plug wires, new dist cap and rotor, new air filter, new oil and filter, new fuel filter, new PCV valve. All replacement parts are the high end good stuff (sister in law gets stuff for me at cost).

Problem: Fails hydrocarbon emissions idle test.

There are no codes in the computer.

Runs super clean and sweet at anything above idle.

I noted that after the new cooling system was installed that she runs cooler than the 200 degrees that has been the norm since I bought her new.

I didn't replace the thermostat when I did the radiator and water pump because everything looked pristine as I've been religious about keeping the cooling system squeeky clean.

I figure before I look at replacing the catalytic converter I'd ask to see if the reduced operating temperature could be the cause or not.

Any help would be greatly appreciated.

RM

[GMMerlin]

Runs super clean and sweet at anything above idle.

Does this mean it runs rough at idle?

Excess Hydrocarbons are caused by raw unburnt fuel.

[millerrl]

Originally Posted by GMMerlin

Does this mean it runs rough at idle?

Excess Hydrocarbons are caused by raw unburnt fuel.

She actually idles really smooth too.

She gets on down the road REALLY quick and the gas mileage is pretty good too (~25+ on the highway). How can a van that runs so sweet fail the idle emissions test.

My thinking is that if the motor never reaches operating temperature will the computer continue to run rich trying to warm it up?

I bought her new and have burned only Chevron gas and added fuel injector cleaner to the tank quarterly since 1995. Castrol GTX oil and Fram filters always every 3K miles.

If the Cat converter is bad will it give a code to the computer????

Thanks for the reply - if something strikes you please let me know.

RM

[evil_motors]

welll 2 things.. quit using the injector cleaner.. you are hurting your injectors.. that stuff doesnt work anyways.. the chemicals in the gasoline should keep them pretty clean.. you definately dont need to do it quarterly.. maybe at most once a year.. i have personally never used it and my van has 275k miles.. and runs like a top.. if you really want your injectors to be clean take them to a shop and have them clean them.. it will cost about as much as you are wasting with the cleaner and they will be way better off..

secondly quit using fram oil filters unless you want to replace your engine eventually.. i personally would use a sock before i screw one of those failures on my van.. i have seen and heard too many horror stories being in the automotive industry.. just letting you know.

HC is only failed by ignition problems or very excessive lean condition.

[Kings-x59]

evil, other than Fram, what oil filter would you recommend?

[Kings-x59]

oh...
millerri, if your engine is running cool, it will run rich, which will produce excess hyrdrocarbons in exhaust.
Was the thermostat replaced? If it is a lower temp thermostat than stock, that would account for the lower operating temperature. Until the engine reaches its normal operating temp. the 'puter will run it rich.

[evil_motors]

well just about anything but fram.. i usually use purolator..

[e7ats]

Yes a cool running engine will run high on HC's. Get that taken care off first.

If the engine was running kind of rough at idle or hard starting I would start blaming the CPI (spider). There is a fuel regulator mounted right on the CPI, they tend to leak and the fuel is sucked into the intake.

If you live a short distance from the testing center and only drove it maybe a minute or 2 the cat. did not have enough time to warm up. Low engine temps don't help the cat. performance either. A cold cat will not be able to burn up those extra HC's.

Hopes this helps.

About the Injector cleaner, I would use it every other oil change,6,000 miles. Yes todays gas has cleaners in it but the injector cleaner goes the extra mile. Injector cleaner doesn't just clean the injectors, it cleans intake passages and the valves.

[millerrl]

Thanks everyone for the replies.

I'm very fond of my 95 Astro and want to keep her for as long as possible. It's a LT with all the goodies on it and she's still in pristine condition.

In defense of my using injector cleaners... I use the Techron cleaner that Chevron puts out. I can buy a four pack in Costco for a little over four bucks. This will last me a full year.

I drive 600+ miles a week commuting to work and other errands. So that works out to one bottle of cleaner every 7,200 miles. It has a nice side effect of removing water from the fuel system and it cleans the whole fuel system - not just the injectors.

I have found no fault with Fram oil filters. I work in a laboratory where we can perform Tribology analyses (the study of metals and contaminants in oils). I routinely do particle counts on my engine oil and have even photographed some of the particles using a scanning electron microsope. I also change my oil every 1 1/2 months on average due to the high number of miles I commute.

I think before I go spending much more money on parts I'll replace the thermostat and get the operating temperature back up to at least 200 degrees. I'll probably wrap the Cat. Converter with heat tape and bake it out for a couple of days at 300 degrees.

Thanks to everyone for the help!!!!!