So I have recently acquired a 91 gmc Jimmy 5.7 efi. Went to emissions station here in Arizona and missed the NOX part of the test by .09 ( needed to be 5.00 ) nine was 5.09. Looks like the egr valve was replaced probably last year for the test and apparently passed. My question is what other adjustments or tweaks can I make to bring that number down , I've had many other GM trucks in the past all of them carburated and knew how to deal with them . The Jimmy has 125k on it appears to be stock motor everything is in place and correct starts and runs perfectly just this hiccup any help from you gurus on this site would help , thank you.
CK5
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Emissions questions?
- Thread starter Crawdad1968
- Start date
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"The auto/oil study concluded that there was a statistically significant increase in NOx of about 5% with the addition of 10% ethanol."
Maybe switch gas.
Burn up what you got, and put non ethanol gas in it.
Retest.
I know in some locales, premium IS the ethanol blend gas.
Here in Wyoming, premium is the ethanol free gas.
I think they know the snowmobilers will not put a drop of crappy ethanol in their sleds and they demand 91 octane minimum.
Should say on the pump.
"The auto/oil study concluded that there was a statistically significant increase in NOx of about 5% with the addition of 10% ethanol."
Maybe switch gas.
Burn up what you got, and put non ethanol gas in it.
Retest.
I know in some locales, premium IS the ethanol blend gas.
Here in Wyoming, premium is the ethanol free gas.
I think they know the snowmobilers will not put a drop of crappy ethanol in their sleds and they demand 91 octane minimum.
Should say on the pump.
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And for shiggles, run some SeaFoam through the vacuum booster hose. Has helped me before.
Did you make sure your cat was nice and hot before the test?
Believe High NOX is from high combustion temps, perhaps the egr may have failed again or passages are plugged - egr helps cool down combustion. Also, prob make sure the basics fuel/timing are both spot on lean mixtures/timing will change combustion temps. I dont know of any stations in PHX that dont have ethanol. Places outside emissions testing I've run across a few...
Yeah, we are blessed in Wyo.
Ethanol is widely despised here.
People will pay a premium for ethanol free gas.
Boats, snowmobiles, motorcycles, and anything with high compression, or that gets stored 6 months of the year, ethanol will kill.
Particularly chainsaws, wood splitters, and little motorized things with carburetors.
That ethanol leaves a white flakey residue behind when it evaporates.
Okay, all gas does.
But ethanol leaves more.
A lot more.
Maybe you can find a place that has ethanol free.
Ethanol is widely despised here.
People will pay a premium for ethanol free gas.
Boats, snowmobiles, motorcycles, and anything with high compression, or that gets stored 6 months of the year, ethanol will kill.
Particularly chainsaws, wood splitters, and little motorized things with carburetors.
That ethanol leaves a white flakey residue behind when it evaporates.
Okay, all gas does.
But ethanol leaves more.
A lot more.
Maybe you can find a place that has ethanol free.
Meeeoowww...
That would be nice, I paid more than that the other day for ethanol in my G8... PHX is one of the few places that doesn't share formulation w/ any other region. Prob because our smog gets bad and the high temps. Never really got a straight answer on that though.
You know what they say about felines;
A big Cat may bite,
But a little pussy cat wouldn't hurt anyone.
Nah, they just screw anyone in or near the big cities.
I used to live in the most expensive and most populated
place in America.
You would think with 38 million people, there would be some sort of purchasing power.
No.
The opposite is true.
They know the working people have no choice but to buy gas.
So they screw you.
Now i live in the least populated state.
Also the lowest cost of living.
No such games are played.
I don't have an answer.
I just packed everything into a rusty 1976 K5 blazer with a 400 small block and pointed the front end East.
I never shared their values anyway, so i brought no baggage.
What does this have to do with passing smog?
Everything.
No emissions bull crap here.
If you still need to pass NOx, back your base timing 2-3, you can increase the gap on the plug @ .010.
At idle try to open egr, either by hand or with external vacuum sorce.(wear gloves will be hot), if stalls or runs poor egr passages are clear. Need to check egr control, I think the ecm on the 91 only commands egr vacuum solenoid.
Also make sure cooling system is in good shape. X2 as important in AZ.
At idle try to open egr, either by hand or with external vacuum sorce.(wear gloves will be hot), if stalls or runs poor egr passages are clear. Need to check egr control, I think the ecm on the 91 only commands egr vacuum solenoid.
Also make sure cooling system is in good shape. X2 as important in AZ.
Back when I had to pass an emission test,with my big block powered trucks (and small blocks too),I would wait until the gas tank was under 1/4 full,and dump in 3 bottles of dry gas ( isopropanol works better than methanol based stuff),then go for a good blast down the highway on the way to the inspection garage..
As long as you didn't have to sit in a line there waiting to get in the inspection bay and the tailpipe sniffed,I passed with flying colors..
A few times one guy I went to had to pull the PCV valve out of the valve cover and retard the timing,and turned up the idle speed a bit, on one 454 I had to get it to read below the allowable limits..
That engine had a camshaft replaced and I think it was a slightly higher lift & duration than stock..engine was bone stock otherwise.
Now anything over 15 years old here is exempt from emission testing..Thank Jesus..!..
As long as you didn't have to sit in a line there waiting to get in the inspection bay and the tailpipe sniffed,I passed with flying colors..
A few times one guy I went to had to pull the PCV valve out of the valve cover and retard the timing,and turned up the idle speed a bit, on one 454 I had to get it to read below the allowable limits..
That engine had a camshaft replaced and I think it was a slightly higher lift & duration than stock..engine was bone stock otherwise.
Now anything over 15 years old here is exempt from emission testing..Thank Jesus..!..
Thanks this advice sounds just like what i needed, I checked the egr by pushing on the rubber part and it almost instantly stalled. I have a new vac control solenoid on the way and hoping that is the problem. I pulled on the wires to unplug it and they pulled away from the clip, one is pink one brown or black , I managed to put the wires back in the clip but was unsure which way they went( pink on top or bottom?) Any how the part should be here tomorrow and I will proceed with the diagnosis and or fix . Thanks for replying!
Man if you were that close, I would just make sure you don't have any vacuum leaks, and then get the catalytic converter extremely hot right before the test like everyone else is saying. Go wide open throttle several times and then pull up to the smog shop and leave it running. If there are any cars at all ahead of you, then leave and come back again when there is nobody waiting
Sounds like a plan! Thanks I'll do that for sure!
This is good advice, for any smog test. Always want a nice hot cat.
