Smog Failed- Idle Emissions- looking for advice (vehicles, auto, van)

[nighthouse66]

hi guys, this is probably a common question for all you gearheads out there, and since i can't find anything about my particular van i am throwing it to you guys.

i have a 1995 Vandura, 8 cylinder. i have maintained it very well and it passed all the smog stuff except one part of the idle emissions test. i am gonna try and type it out just as it is on the paper from the smog dude.

Test- HC (PPM)
Idle MAX MEAS
100 222

All the other stuff passed, as i said. I am a pretty good gearhead for a chick- i have done my own shocks, wires, tune-ups, and if i can get a good handle on what this might mean i would rather fix it myself (with the help of roommate/gearhead if need be) than to walk in without specifics into an auto place that may rip me off and charge me for the pleasure. I have never had the oxygen sensor replaced, tho i did have to have it on my previous G2500 chevy van, 1994. I lived in the desert for a year and i haven't changed the air filter. could this be something as simple as that? ideas are appreciated, i will name my first born after you.

[M3 Mitch]

Possible that just changing your oil will get you to pass, but maybe not. If your O2 sensor is way old a new one will pay you back in MPG anyway.

A very fresh set of sparkplugs, with say less than 100 miles on them, tend to get HC down.

If you have the time, run a tank full of gas with one bottle of Techron through the van, run it all the way from 4/4 to 1/4 tank full without adding gas, more short trips the better.

Air filter would not hurt but in most FI it has little effect - but in general catch up your deferred maintenance and that should probably get you to pass.

[rbohm]

start with the basics, check the air filter and see how dirty it is. if you have any question about it, replace it they are cheap.

change the oil before you go back, often times because of emissions controls, you will get a little oil burning, not enough to notice visibly but enough for the emissions sensors to pick up on and show a slightly higher HC reading.

third, track down any vacuum leaks and repair them regardless of how small they are. you might be getting a slight lean miss, and that will also show a higher HC reading. you can use something like an unlit propane torch, let the gas flow over a suspected area, or perhaps some WD40. at any rate the engine will smooth out when the vacuum leak is found using either of these two methods. and it can be something as stupid as a cracked vacuum line.

after that check you ignition timing and advance it to about 10 degrees initial timing at idle.

clean the idle air control passages in the throttle body.

run a can of injector cleaner through the system.

[M3 Mitch]

Actually the oil needs to be fresh because used oil typically has some unburnt condensed gasoline in it, and the PCV system adds this to the intake air. In theory the FI system will compensate for this perfectly but as you know in practice nothing works perfectly.

Depending on how this particular FI system works, I guess the air filter *might* cause it to run a bit rich at idle if it's badly clogged but I would think if the ECM is out of "trim" on the fuel there would be a Check Engine light on.

BTW OP see if you can read any codes the van may have stored. Not that they are the "law and prophets" but it's good info and can be obtained for free at many chain parts stores.

MY 95 vehicles can be OBD-I, OBD-II, or even sort of a hybrid "OBD - 1.5" (the last one I have heard of but never seen myself so it may be BS)

[curly5759]

It would help to do a backseat diagnosis if we had the rest of the numbers, Co,Nox etc, even if they passed.

Changing the oil will most likely help, and making sure your base engine is running properly-- Plugs, cap, rotor, plug wires,etc.

Do you have a check engine light on? If so, can you post the code?

curly

[usafracer]

You need to change your air filter. Your van uses a speed density system. There is no Mass Air meter. With out going into too much detail a little restriction can cause it to run rich and rich is excess HC.