Emissions Test: Better To Full Or Low Tank Of Gas?

[ULVER]

I'm thinking it doesn't matter but I was curious. Anything else help with passing? Fresh oil change? Anything?

This vehicle has always passed, but it's 14 years old now, and the CEL comes on constantly, though the car drives smooth as silk. I know it's an instant "no pass" if it comes on during the test.

I replaced the 0'2 just last year. The cats have never been replaced. I do know MPG is low, though the car have been nicely tunes, and I run synthetic oil.

Thanks for any thoughts... I would hate to have to throw any more $$$ into it, as I plan to get rid of her this year.

 

[mikered30]

What is the code it is throwing?

 

[bdcardinal]

exactly, whats the code? what does emissions testing consist of there?

 

[Turk]

Yea, the code would be good to know.

Gas amount shouldn't matter, but I would have close to 100% top tier gas, fresh tune-up, PCV valve, oil change would be nice too.

AND... take it out on a long run & rev it up some to help clean out the engine - then bring 'er in for the test...

Good luck!

 

[JHZR2]

Cant see how level in the tank would matter, unless you were diluting out something you did want in there, or adding more of something you dont (e.g. sometimes people put alcohol/drygas in to reduce combustion temps to help pass).

Generally good tune, all systems go, and fresh gas should be all it needs. The fact that there is a CEL might be something silly, like the o-ring or tightness of the gas cap. Need to know what it is so we can help.

JMH

 

[Vilan]

Try to drive it around the highway for a half hour or so to get the cats toasty warm before testing. And show up at the test station at a time when few others are there so the cat won't cool off waiting. New spark plugs might help. Beyond that... since you plan on getting rid of it soon anyway, it's probably better to spend your money on a bus pass than any serious repairs.

 

[ULVER]

Thanks for the thoughts... I have NEVER found out what the "codes" thrown are related to!

Autozone told me that their machine couldn't read codes on a car as old as a '94.

Last year, I "passed" and the CEL light came on as I was leaving the station.

And, had been on the day prior.

I guess I will get her nice & hot, and give it a shot!

 

[dwendt44]

That car maybe was made before OBD-II.
There's a trick with a paper clip and the diagnostic terminal that you count the flashes and read the problem from a chart.
I'm not explaining it well.
But some one here knows what I'm talking about.

 

[steve20]

you can use the paper clip to ground the diagnostic terminals it is safe to ground any 2 terminals until the CEL starts to flash. The first reading will be a 12 which is normal (one long flash and two shorter ones = 12). Any other codes it shows are not normal write them down

 

[mechtech2]

Any stored code will cause a fail. It does not have to be on or flashing.
Codes can be read for free at an Auto Zone parts store, or others.
They can tell you what needs fixing, and clear the memory.
That would be the next step.

 

[Gary Allan]

The CEL may have nothing to do with emission on an OBDI car. You can have an overheat condition as determined by the PCM versus what the temp SENDER is reading. My daughter's Taurus's CEL will sometimes come on with some extended idling (the temps gauge swings appropriately) but the CEL extinguishes itself after motion gets coolant flow up (that's the way I've reasoned it anyway). It could surely be something else, but lots of stuff is tied into the CEL light (including low oil pressure - but it does have its own light too). The oddity of OBDI is that the two indicators aren't even connected to each other ..and, therefore, don't have to see the same data.

 

[ULVER]

I don't tknow if this is true with cars in general, but several fleet managers have told me, that the P/I's are notorious for having "phantom" CEL's. Some said that if the cars are running fine, they just put electrical tape over them.

Is it a given, that cats are history, with close 200K on them? Would they be the reson for less than stellar MPG, or it that natural with a car 14 years-old?

Thanks...again

 

[SecondMonkey]

Originally Posted By: ULVER
Last year, I "passed" and the CEL light came on as I was leaving the station.

And, had been on the day prior.


LOL, I just had to have mine tested, the CEL came on when I was half way to the testing place.

I drove from parking lot to parking lot stoping and starting about 30 times before it would go off.

A good way to pass would be to make sure you're using gas with 10% ethanol, if available, and add a pint of 90% isopropyl alcohol from the drug store to 1/4 tank. The alcohol will make it burn cleaner.

 

[SecondMonkey]

Originally Posted By: ULVER
Is it a given, that cats are history, with close 200K on them? Would they be the reson for less than stellar MPG, or it that natural with a car 14 years-old?


I wouldn't say it's a given, but my guess would be they are about done, and yes, they could be clogged and causing bad mileage/emissions.

 

[eljefino]

90% drugstore alcohol is 10% water! Use iso-HEET if you feel you need to add alcohol to your gas.

Missed what make car this was.

May want to read the inspection laws for your state; lots will do an OBD-II computer scan for 96+ and a tailpipe sniff, with NO computer scan, for the 95 and older. So electric tape on the CEL may work for you... provided your tailpipe emissions are up to par.

The paper clip across two terminals test works for GM but fords and imports need a voltmeter or ???. Dodge needs 3 key flips in 5 seconds, super easy.

 

[eljefino]

If this is a crown vic with the 4.6, the oil burning from the valve seals could have poisoned your cat...

I'd have said o2, but you put in a new one a year ago... sometimes they cool off more than the computer thinks is allowed and throw phantom always rich/lean codes. I get this driving down long hills sometimes.

 

[shoz123]

If it's an EGR code you can usually pull the SPOUT connector and retard timing 3-4 degrees. This will help with the NOx emissions.

 

[NYEngineer]

A friend with a Jeep asked to borrow my code reader. He called and said it had insufficient flow in the evap system, or whatever the exact words were. I told him try filling it up and if that doesn't make the light go out, swap on a new gas cap. The higher fuel level cleared the code. I guess the system pulling on a decreased area increased the signal?

 

[ULVER]

I passed! I passed!
CEL didn't come on... Tech said the numbers were fine...

I still think the cats could be shot, but I'm good for this year, and very likely the last for the old boat anyway.

Thanks for all the thoughts!

 

[eljefino]

Originally Posted By: NYEngineer
A friend with a Jeep asked to borrow my code reader. He called and said it had insufficient flow in the evap system, or whatever the exact words were. I told him try filling it up and if that doesn't make the light go out, swap on a new gas cap. The higher fuel level cleared the code. I guess the system pulling on a decreased area increased the signal?


On GMs the evap pressure test, or whatever they call it, only runs from ~1/4 to 3/4 of a tank, and at air temps above ~freezing. So if one has a problem they can likely mask it by always topping the car off, getting smogged in the winter, or hacking the intake air temp to read 20'F.

Up here you can have two or three I/M monitors "not ready" and still pass, the gas cap one is the last to run, so it seems doable.