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Disgruntled..... Emissions troubles

chevyaddict

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Jun 12, 2002
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894
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Tucson, AZ USA
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1990 Convertible
Hi all; Long time no write! I was hoping someone could help me out here because I am at my wits end. My 84 won't pass emissions - it passed fine last year but this year it is failing in both CO and MO. I have replaced the following items thus far:

Oxygen sensor
EGR valve
Plug/Wires
Catalytic Converter
Throttle position sensor (only because this code is occassionally punched out)
I even tried running alcohol through it once to make it run leaner

No other codes ever show and the car runs well save for idling alittle slow. It has 158,000 miles on it but doesn't burn any oil and still runs great. Could it be time for new throttle bodies? Should I try rebuilding them? Is there something else i am missing?

I loath car garages and don't trust taking the car there. Any suggestions??
Thanks much
Dawn
 

garycr14

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Aug 31, 2002
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260
Location
Newark, CA
Corvette
1994 Torch Red Coupe, 1981 Blue Coupe, 1973 Orange
Hi, You didn't mention by how much it is failling the test by. A new air filter or recharged K&N air filter might help. I always chnged the oil before I do the smog test, pvc valve. Just some things to look at if it is just missing.
 

garycr14

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Messages
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Newark, CA
Corvette
1994 Torch Red Coupe, 1981 Blue Coupe, 1973 Orange
Just noticed your "81". Do you really have the only actual paint code 24 "81"?
 

chevyaddict

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Messages
894
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Tucson, AZ USA
Corvette
1990 Convertible
Thanks, but it has definitely had an entire tune- and then some. :) It is actually almost double over the limit - which is odd considering last year it was within limits.

Ah yes, the 81. Well, lets say I spent two years of my life trying to determine if it was "the one" and all evidence I have so far points to it. I don't have a complete build sheet because the one off the gas tank was rubbed in certain areas. The code plate was taken because the car had been stolen during its stent with the 2nd owner. The only way I can find out for sure now is to take the entire car apart to find another "hopeful" build sheet. The 2nd owner had it from 84 until I purchased it and had never repainted it. Also, the originial owner kept it quite pristine. You can see the body seems underneath the faded point. All the other evidence I have (location of build, sequence of vin, etc) points that it is indeed "the car". The original owner did order it special in California. :)
Dawn
 

-=Jeff=-

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Feb 2, 2001
Messages
909
Location
Bartlett, IL. (Chicago Suburb)
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1990 ZR-1
I am wondering if the TBs need cleaning, not rebuilding just yet. Also you might want the injectors cleaned and tested. Maybe one or both are leaking a bit.

Just an Idea..
 
Joined
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Tallahassee, FL
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none right now :(
Cleaning the TB sounds good to me too...

How hot was the car when you had it tested? it helps if it is as hot as possible (safely possible). It may help to put a bottle of techron in the gas to clean the injectors the easy way.
 

chevyaddict

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Messages
894
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Tucson, AZ USA
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1990 Convertible
Ooohh, I didn't even think about leaky injectors! Is there an easy way to determine if that is happening? That might explain the low idle too because it would be bogging it down a bit.

Also, is taking these things apart and cleaning them similar to a holley carburetor rebuild? I'm a pro at holleys......... but nothing else. :(
Dawn
 

garycr14

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Messages
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Location
Newark, CA
Corvette
1994 Torch Red Coupe, 1981 Blue Coupe, 1973 Orange
chevyaddict said:
Ah yes, the 81. Well, lets say I spent two years of my life trying to determine if it was "the one" and all evidence I have so far points to it. I don't have a complete build sheet because the one off the gas tank was rubbed in certain areas. Dawn
Have you check in the seats? Years ago I used to do custom auto upholstry, and in almost every car a build sheet would be in one of the seats. I will be tearing mine down in the next couple of weeks to redo, if I find my sheet inside I'll let you know. If it where I, I'd realy like to know if I had the "1".:beer
 

vetteboy86

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May 26, 2003
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IN
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1986 Black "Indy 500 Pace car replica"
I too have heard that having the test done when the car is as hot as possible would help lower the numbers. I was instructed by C4C5 specialist that it is a good idea and safe to run two bottles of Chevron Techron in one tank of gas every 6000 miles. On a side note I have an old Trans Am and was talking to another Trans Am owner. He instructed me that i can contact Pontiac Historic Society and for around 50 order in information packet. I would supply them the VIN and they would send me the window sticker, build sheet and other info about the car and the model year. I am not aware of any other company doing that. I thought that was great, and I hope other companies will pick up that idea.

The best of luck
Craig
 

chevyaddict

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894
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Tucson, AZ USA
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1990 Convertible
Believe me - I tried all those suggestions already. The problem is that it came from the plant that burned down; therefore the records were destroyed. I tried ordering the window sticker already - dead end there too. I even tracked down the original dealership in California. It was sold off 20 years go. I even tracked down the dealership owner just to found out he had died six months previously...... But the SEATS!! Now that offers me some hope!! Let me know if you find them there! The car is so pristine and original, I just haven't had the heart yet to tear into it. Still purring like a kitten!!! Just faded rrreeeeeaaaalllllyyyy bad. Don't want to repaint it either until I find out definitely or not either. :) Thanks for the suggestions though! If you think of more please pass them on. Perhaps you'll think of something that I haven't!!
 

Mad-Mic

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1987 Redskin Red Coupe
is it blowing any smoke when you step down on it? i'm thinking if it passed last time and is double now maybe you have some serious blow by the rings or a head gasket starting to go south on you. also you might want to try and retard your timing back a few degrees.
 

chevyaddict

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actually, I should have clarified - it passes under load but fails at an idle....
 

chevyaddict

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Tucson, AZ USA
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1990 Convertible
Nothing disabled on this car - no by-passing (I do that to the race cars... :); nor do I want to disable anything. Here are the readings:

HC Loaded 178 (standard is 220); idle 495
CO Loaded 1.08 (standard is 1.20); idle 3.91

It also idles slow (550) and the throttle position sensor occasionally overreacts (which I have replaced - didn't fix the problem) and makes it idle high while making the light come on. This is intermittent though...... Is there another switch or something or would it just behoove me to rebuild the TBI's?
 

KANE

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Dark Blue 1982 Trans Am(s): Polo Green 1995 MN6
chevyaddict said:
It also idles slow (550) and the throttle position sensor occasionally overreacts (which I have replaced - didn't fix the problem) and makes it idle high while making the light come on.
Sounds like the idle speed and CCC are out of sync. TPS and the idle set screw can be heck and seem to work against each other if minimum idle speed is not set to eachother.

Is the harness okay from the TPS to the firewall and to the CPU?
Are the contacts okay in the TPS?
Is the shaft loose for the throttle blades (FALSE AIR)?
Vacuum leak at tranny modulator FALSE AIR)?
EGR sticking?
Bad dirverter?
Coil / module / advance?

chevyaddict said:
This is intermittent though...... Is there another switch or something or would it just behoove me to rebuild the TBI's?
I would rebuild it and set everything back to the factory setting to start with. Couldn't hurt.

I put TPI into a 78 and then went through the emmissions game with Vettes in North Carolina. It took a while to get it right- lots of dorking with the sensors, set screws, false air, IAT woes, TPS, MAP sensors, lack of fuel pressure at high RPMs..... I wouldn't trade the experience of it for the world!!
 

KANE

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Dark Blue 1982 Trans Am(s): Polo Green 1995 MN6
chevyaddict said:
What is AIR exactly?
Smog pump and assoc. hoses and valves.
 

KOPBET

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Jan 31, 2003
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Tulsey Town
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'73 Silver LS4 4 speed
chevyaddict said:
What is AIR exactly?
It's a carryover term for Air Injection Reaction. It's really Secondary Air Injection. An air pump pumps air directly into the exhaust manifold to help with burning of incompletly combusted fuel mixture during warm up. This helps burn HC and CO resulting from rich starting mixtures. This burning helps with more rapid heating of heat dependent oxygen sensors and cats. If AIR is not removed after warm-up it can cause the oxygen sensors to provide false lean signals, hence a richer mixture, poor economy and, high HC, CO. AIR inoperative during warm-up could result in high HC, CO during warm-up.

At least that's how I understand it. If I'm wrong then perhaps someone will let me know.
 

chevyaddict

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894
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Tucson, AZ USA
Corvette
1990 Convertible
OOOHHHH!! Well, the smog pump itself has also been replaced, but it sounds like there may be another "sensor" that is supposed to function after the car warms up. Could be that it is malfunctioning - especially considering it is at an idle that things are awry. I'll check that out.

Also, the TPS thing - this intermittent - hard stopping usually makes it "malfunction", causing the code 22 (I believe) to come on and the car to idle really high. 85% of the time it works properly and the times I went through emissions it was operating fine. STILL, definitely running tooooo rich at an idle.

Again most of this stuff has been replaced, but I guess that doesn't mean they are by default, "working". I'll check the vacuum leak thing too - didn't think about the tranny modulator. The car runs so well I hate to mess with the TBI's if I don't have to. :)

THANKS EVERYONE!..... I'll keep you posted.
 

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