k well i still cant get my car to pass emissions though i had a huge improvement over the last test. Standard is .80Hc and 15 CO.

First Try
HC 2.20 Co 11.9

Second try after replacing plugs, wires, cap/rotor, tps set at .54, replacing intake gaskets cuz of a small leak, o2 sensor new, cts sensor new, timing set at 6*
Hc 1.04 Co 3.7

I cant figure out why the car wont pass the emissions. It passes everything on the graph except from idle to about 10 mph. After that it falls below the standard and would pass easily.

Ever since i bought the car it has had a bad stumble when it first started. After about 5 minutes of warming up it stops. However, the idle is a bit rough but the hesitation and surging goes away. THough it was a vaccum leak but its not that. Fuel regualtor is good. Not sure on the injectors but it almost runs prefect after a few minutes of warmup nad their is no sputting on acceleration or deceleration. I NEED SOME HELP IM REALLY GETTING FED UP WITH THIS. Help would be aprreciated thanks!

 

Been working on the same problem myself.....with the rough idle anyway...
Passed emissions with no problem....Have you cleaned out your IAC passages /replace IAC valve....alot of carbon buildup in there will cause a rough idle and not allow the IAC valve to function correctly...I was having a part throttle stumble and miss/rough idle,and I cleaned up the connector on the coil(looked rough) and put in a new IAC valve...the part throttle miss is gone but still a little rough idle...so I'm going back and cleaning up the passage way a liitle/and behind the throttle plates with some gum cutter (what I should have done in the first place)and see what happens...Woudn't hurt to try that...unless you have already.
You got a new/old cat?

 

I would check to make sure that the fuel pressure is correct and that all of the injectors are operating correctly(especially if the car has over 100,000 miles on it). Also make sure the cat is doing its job.

 

Yeah, the cat being hot helps a lot. Make sure you drive it around for at least 20-30 minutes before you go in for the test, and don't turn it off while waiting for your turn on the test stand. Warm cats are a lot more efficient!

If they have over 100k miles on them replacements might help a lot, too (though expensive - especially if you have dual cats like I do!)

If you have an AFPR, you could always drop the pressure a little just for the test as well.

Have a Great Day!!!


- Vern

 

RedLine fuel injector cleaner (Pep Boys) tends to do a good job, might be worth running a tank full of gas + this thru the car before your next test.

My neighbor's Expedition was acting funny, hesitating, hard to start, etc. We hooked up a scanner and saw his Long Term Fuel Trims were whacko...2% for one bank, 11% for the other bank. Clearly a fuel delivery problem somewhere on the 11% bank.

We figured we'd try running injector cleaner thru the tank before pulling the injectors (major PITA on the Expedition) and sure enough it worked. After a week of running gas + RedLine cleaner, his Trims had balanced back out to 2%/2% and it was running smoothly.

 

jd, I remember responding to your stumble problem awhile back. I suggested it might be your cat. And since you're not passing emissions either, I think that reinforces that you might need a new one.

But if you don't change it, then as already said, drive your car for quite awhile to get it good and hot right before your test. Don't idle it, drive it. That'll get your cat flowing well and will get all your gas fumes cleared out too.

Your stumble is caused in a similar way. If the cat is old, then until it warms up, it's like it's partially melted down or clogged. So your exhaust doesn't flow well.

Change your cat, and I'll be your stumble goes away, and you're likely to pass your test too.

 

Sounds like you may have checked this, but I think its worth mentioning:

There is a vacuum line on the fuel pressure regulator that allows for lower fuel pressure at high vacuum conditions (i.e. not too much throttle, like idle/low speed) and the injector pulse width is set from the factory with this lower pressure in mind. If the line has a leak the fuel pressure may be higher than it should be at part throttle, allowing 'unaccounted for' extra fuel into the motor. This could be why your car has high HC at part throttle, it may be running rich.

Not saying this definitely is the issue with your car; but worth a try. I think the best way to verify this is working properly is to hook up a fuel pressure gauge to the rail and verify the pressure this way, check it at idle with the vacuum line on, then pull off the vacuum line. Specs should be in a service manual (I'm at work, don't have the manual here). Also, when all else fails a new cat is a great idea--not too expensive (if you install yourself) and from the looks of it you're not failing by much so it would probably make enough difference to pass it, giving you more time to look for any other issues w/o worrying about the smog ***** suspending your license (Thats what they do in IL for those in other states).

Again, pardon me if you've already done this

Good luck.

 

Well the cat was replaced about 1 1/2 ago so i dont think that is the problem. Ive taking it to 2 muffler shops and both said the cat is not my problem. Checked the fuel regulator line and there was only a hint of gas smell but no gas in it. Fuel injectors look to have been replaced. The idle control was something i was gonna look into, when i shut the car off i get a loud hiss from it. Im thinking its either an injector or the idle control but im not sure. If i had a leaky injector wouldnt that cause me to fail all over the place on the test not just idle?

 

Okay, first let me say this response rivals War and Peace in length; sorry, I’m bad at explaining ideas sometimes.

If you didn't find gas in the line all that means is the regulator itself is not leaking fuel through the diaphragm, it may still be leaking vacuum.

I'm saying you want to check to see if FPR is getting the proper vacuum signal in order to lower the fuel pressure at high vacuum conditions. High vacuum conditions=low load operation. If the line itself is leaking vacuum you may not know it by just looking at it.

If the line is leaking vacuum, the injectors will supply more fuel than the engine needs at idle/low load because fuel pressure is too high in this operating range. Since the vacuum line is what controls the required fuel pressure reduction at low loads, an easy way to check if the vacuum line is working properly is to check the fuel pressure at idle. Also, it may not be enough to simply check whether its lower at idle with the vac line attached, check if it is to specifications at idle (a service manual should provide the specs). I would first connect a fuel pressure gauge to the fuel rail, then turn the key to the ‘on’ position for like 5 seconds a few times but don’t start the car. Then go look at the pressure on the gauge and compare it to the spec for pressure w/o vacuum. If its lower or you see the pressure dropping you have a leak in the system, probably an injector. Next, with the gauge still attached, start the car, look at the gauge and compare it to the idle fuel pressure spec. If its higher than the spec by more than 1 PSI or so the FPR isn’t being supplied with enough vacuum and you may have a vacuum leak in the line (replace the line and check again).

If one or more injector is leaking a little it may be possible that at higher engine speeds the amount of extra fuel is not enough to cause a problem, while at lower speeds it is. You might be able to determine which is leaking by letting it idle for a while, then checking the plugs—if any are darker than the others, I’d suspect that cylinder’s injector.

I wouldn’t be surprised if an injector(s) is(are) bad; GM had issues with them back then.

If it was me, I'd do all these checks. If none of these issues are the problem and the emissions date was fast approaching, I'd set the timing to factory spec, get an adjustable fuel pressure regulator & lower fuel pressure to where it will run just out of detonation up to 1/2 throttle (I don't think the IM240 uses more than ~1/3 throttle), fill up a 1/4 tank with gas, add a few gallons of methanol/ethanol, make sure the car is warm & get it tested. Again, you're not failing by much so it may be enough (IL doesn't test for NOx). Once you pass the test I'd set fuel pressure back to normal & fill the rest of the tank with gas. Now you're not under pressure and can find the issue at your leisure.

HTH, sorry for the long post.

 

thanks for all the replies. I had the fuel pressure tested after it was warmed up at a shop and they said it was right around perfect. I may jsut change the injectors alter on but i will def. d what u suggested 377 thanks to everyone