CarburetorsCarb discussion and questions. Upgrading your Third Gen's carburetor, swapping TBI to carburetor, or TPI to carburetor? Need LG4 or H.O. info? Post it here.
Welcome to ThirdGen.org!
Welcome to ThirdGen.org.
You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, at no cost, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, join the ThirdGen.org community today!
yup, california doesnt want me to drive... the 2500 rpm test showed 90 hc but its super rich on idle. 305 quadrajet, anybody have any tips, im trying to pass smog, thanks
Is everything set to factory spec, like the MCS dwell? How fresh is the ignition tune-up?
im going to use new sparkplugs tomorrow, the only reason i havent timed it yet, is i heard you have to unplug some connector, i have no clue where that it. also i was thiking the idle mixture adjustment might help me out.
The connector you have to unplug to set the timing is a flat 4-wire that goes from the distributor base to the firewall harness ('82-'86 large cap HEI, that is). It has a habit of hiding from you.
High HC is caused by unburnt or partially-burnt fuel - a misfire. It isn't uncommon for weak spark plug or weak spark plug wires to cause a misfire at idle. Leaking exhaust valves will also cause it.
i will do all that, by the way what am i looking for on the rotor and cap? also my co (carbon monoxide) is 1.49 at the 2500 rpm test, max is 1.2, what can i do to help lower that number?
Look for carbon build-up on the cap/rotor terminals, and carbon tracks on the cap/rotor insulator material. If you don't know when they were last changed, it's a good bet they need to be.
CO is a rich mixture. A weak O2 sensor is the #1 culprit there - and it may not set a trouble code. The story here is the same as the cap & rotor - if you don't know how old it is, replace it.
Also make sure the choke is opening all the way. Check to see if you have excessive blow-by that is being put back into the air/fuel mixture (a fresh oil change can do wonders here). Have a fresh air filter installed (probably not a cause with a feedback carb, though).
Q-jets are also known to have leaks from the well plugs on the bottom of the fuel bowl/main body. The "cure" is to clean them thoroughly (which requires some carb disassembly) and cover them with epoxy. I'd go through all of the other things above before going there, though.
Let me tell you a personal story to encourage you a little here. 2 years ago, I bought Berlinetta #2, '82 LG4 computer q-jet, all stock, from the Martinez area. This was an eBay purchase sight-unseen, so all I cared about is that it was what they said it was in the ad, and that it would make the trip back home. It had 300k unrebuilt miles on it (I wasn't too concerned about that because I planned on removing the entire drivetrain, anyway).
I discovered the previous owner had gone through a bunch of hoops to get it past the same smog tests you failed. It had a professionally rebuilt carb, new O2 sensor, new EGR valve, new A.I.R. pump and check valves, new cat. The seller was a charity donation outfit, and the guy had the car running and warmed up when I arrived. I found out the next morning why he did that - the choke had been tied open and it was extremely difficult to get started and keep running when cold. The idle was terrible, barely acceptable when warm and too high then.
I bought a cheap tool kit from K-Mart and did some basic carb adjustments to get the choke to work and get it to idle better. It still was finicky until warmed up. I took it to our emissions testing station when I got home. I had it nice and warmed up, but when it was my turn, they had me shut it off and get out of the car, and it sat and cooled off for 20 minutes before they got back to it. When the tech pulled it onto the dyno rollers, he couldn't keep it running, so they gave me a no-test (no charge) and sent me on my way.
I took it home and started setting everything to factory specs. I started with the timing, then idle speed, then MCS dwell (adjusted via the idle air bleed, but I had to set the idle mixture screws to their proper place first). The EGR vacuum lines were routed incorrectly, so I straightened that out. After that, it would start immediately hot or cold, idled properly hot or cold, and basically ran just like you would think a stock '82 LG4 auto should.
I took it back to the emissions test station. They didn't have any trouble with it getting it through the test this time - in fact the test was cut short via "fast pass" because the emissions readings in the early part of the test were so low.
So, get these things working the way the factory intended, and they will burn cleanly.
Let me tell you a personal story to encourage you a little here. 2 years ago, I bought Berlinetta #2, '82 LG4 computer q-jet, all stock, from the Martinez area. This was an eBay purchase sight-unseen, so all I cared about is that it was what they said it was in the ad, and that it would make the trip back home. It had 300k unrebuilt miles on it (I wasn't too concerned about that because I planned on removing the entire drivetrain, anyway).
I discovered the previous owner had gone through a bunch of hoops to get it past the same smog tests you failed. It had a professionally rebuilt carb, new O2 sensor, new EGR valve, new A.I.R. pump and check valves, new cat. The seller was a charity donation outfit, and the guy had the car running and warmed up when I arrived. I found out the next morning why he did that - the choke had been tied open and it was extremely difficult to get started and keep running when cold. The idle was terrible, barely acceptable when warm and too high then.
I bought a cheap tool kit from K-Mart and did some basic carb adjustments to get the choke to work and get it to idle better. It still was finicky until warmed up. I took it to our emissions testing station when I got home. I had it nice and warmed up, but when it was my turn, they had me shut it off and get out of the car, and it sat and cooled off for 20 minutes before they got back to it. When the tech pulled it onto the dyno rollers, he couldn't keep it running, so they gave me a no-test (no charge) and sent me on my way.
I took it home and started setting everything to factory specs. I started with the timing, then idle speed, then MCS dwell (adjusted via the idle air bleed, but I had to set the idle mixture screws to their proper place first). The EGR vacuum lines were routed incorrectly, so I straightened that out. After that, it would start immediately hot or cold, idled properly hot or cold, and basically ran just like you would think a stock '82 LG4 auto should.
I took it back to the emissions test station. They didn't have any trouble with it getting it through the test this time - in fact the test was cut short via "fast pass" because the emissions readings in the early part of the test were so low.
So, get these things working the way the factory intended, and they will burn cleanly.
