Please help me lean my mixture on my 87 T/A before I get rid of it. I am now getting a code 45 (rich exhaust). It always sets at cruising speed 60mph, then goes out after I come to a stop. It doesn't stay on all the time, but is getting more frequent. I have spent all weekend with it and this is what I have found.
First plugs were Bosch 4 and 3 of them were loose. I changed with new A/C Delco plugs at .035gap. Now my lifter ticking noise is gone, was coming from the plugs loose the whole time. Took it back on the road after letting it idle in Drive for about 15 minutes, still getting code 45 on highway. Brought it back home and removed and plugged all fuel vapor hoses and egr from carb, so I am working with just the carb. I hooked up a dwell meter to the green connector and here is what I find.
The needle is at 45 degrees and steady. If I smother the carb with a rag, the needle will not go up. If I pull the brake vacuum line, the needle goes down to 20 degrees. Reconnect the line and it slowly and smoothly goes up to 45 again. I am guessing that my carb is adjusted too rich. My question is how to go about leaning it out. It is not running too bad, but does have a slight stumble when first accelerating from a stop. I have not touched the mixture screws at the front of the carb. I can't find a tool anywhere that fits those. My haynes book tells me to mess with some adjustments under the air horn of the carb inside of it. Please help me. I am leaving it alone until I hear back from someone who knows these carbs.
Thanks

 

I really don't think you have a carb problem. I think you more likely have a weak spark problem. To rule out the fuel system altogether, make sure you have a new air filter and fuel filter.

Next, you need to look at your cap, rotor, and wires. One weak part will cause a slight misfire which sends raw fuel down the exhaust pipe and the O2 sensor thinks you are running rich.

Sometimes your O2 sensor gets carboned up a little after running rich (like with your old plugs) and just needs to be cleaned or replaced to clear up the code as well.

Did you clear the codes from your computer and then drive it again?

 

Hey thanks for the fast reply. I've got that covered already. New air filter, new fuel filter. I pulled the cap and rotor and checked. They look new. Wires could stand to be changed. Someone threw a no name set of 7mm "premium" wires on it and they look rough, but do not see any arcing at night with them though. My exhaust smells on the rich side too. I have pulled the ECM connector and cleared it and driven it wice with the same result. What to do next?

Forgot to add. I checked TPS operation, it is at .450 at rest and responds smoothly. I have 2 map sensors, one has a vacuum line attatched and the other does not. If I remove the vacuum line from the one and plug the vacuum line the idle gets rough, so they should be OK. I checked my coolant temp sensor. It reads 2K ohms cold and 300 ohms when hot. Don't see anything in my book about what I'm supposed to have.

 

If the carb has been tampered with before search for

"Setting rich and lean stops on a CC-Qjet... good tip!" by Damon

Will get you pretty close.

See also:

https://www.thirdgen.org/forums/carb...s-problem.html

 

One is the baro sensor (pass side), used to take an atmospheric reading as a base line for the map (actually Vac) sensor. The baro sensor should not have a vacuum line connected, so you're good. Disconnecting the pigtail to the CTS will 'confuse' the ecm into thinking the engine is fully warm, and is a good check for a failed CTS.

Have you tried to make adjustments to the Idle Air Bleed in the center of the airhorn and see how it affects dwell?

I would think that an ignition problem bad enough to cause a constant rich condition would be noticeable in other ways, but I could be (and have been in the past) wrong. Once you rule out ignition and if IAB adjustment doesn't bring the dwell in (without massive turns), I'd be thinking needle/seat/float level.

 

When I turn the ign. key to the run pos. my M/C solonoid will click for around 20 sec. as a test. Does yours do that??

Auggie

 

Man, thanks to all of you helping me with this. I am a refrigeration mechanic, not an automobile mechanic. Maybe I will be able to repay ya'll with some good A/C or refrigeration advice.
Yes, Auggie, I do still hear my M/C solenoid clicking for about a minute with just the key ON. I read your advice JohnsonM and Naf. I followed the links and printed out some info and went out to the car, armed with some good literature and a tool that I can get to the mixture screws with. Yep, someone has been in there before me, because there was already access to the mixture screws. The IAB on top was still riveted, but isn't now. I turned the mixture screws in and back out 3 turns. Started and let it warm up. Dwell was at 46 until it warmed up and went in closed loop. Then it only went down to 42 and kind of hung there. Disconnect vacuum line and took a few seconds before it started dropping to 10. Reconnected and tried adjusting IAB to get around 30 in DRIVE. Could not be done.
Readjusted mixture to 2 turns out and then let warm back up. I am not seeing the needle bounce around like I'm thinking it should. It just stays put until you create vacuum leak. Then goes down, reconnect line and goes up to around 40 and then back down to 35 and stays there. The literature says that it should be bouncing between 25 and 35, and to aim for 30 in DRIVE. I disconnected the vacuum line again and this time turned the IAB after reconnecting it and the dwell was on the upswing. I could get it to hover right at 30 like it said. Then it just sits there at 30. If you don't create a vacuum leak, the dwell doesn't change until you let it sit there for a few minutes and then jumps back up to 42. I assume this means it cooled down and went back into open loop mode??
Please let me know if this is how this is supposed to be done. I just cleared the ECM and am going for a test run to see if Code 45 comes back.
Again thanks everyone for helping me. I really like this car and kinda like the feedback system, just wish I could understand how it is supposed to be set.

 

Yah, when I check the dwell (six cyl. scale) on my carb the needle will stop moving so I have to run the engine at 2500 rpm to heat the 02 sensor back up to compleat the testing. Code 45 will also be set if the 02 sensor is contamanated with silicone sealer. Maybe the 02 sensor is on its way out? You could disconnect your evap. canister because it could be loaded with fuel and see if the dwell changes??

Auggie

 

Well it still sets the code 45. This is a new A/C Delco O2 Sensor from the dealership. I still have the charcoal canister system unhooked and plugged for testing. It only set at 60mph after a few miles. Did not set code at 70mph after a few miles back. Funny thing is I look down in my carb and can see the pump squirting fuel when I first give it gas. It almost acts like it's getting too much gas from that, but don't think it's the whole problem. It ran good and sounded good, just sets big orange light on dash. Help!

 

I'm thinking internal to the carb, maybe float level. When you pull the vacuum line you're leaning it out enough to get the dwell to respond. How high is it idling? If you disonnect the TPS or M/C does the idle change?

At cruise your throttle is barely open and the ECM is looking to lean the mixture as much as possible. Something is preventing it from adjusting to the rich condition. You've played with idle mixture screws and air bleed.

I'd verify 1/8" of travel for the MC. You can pull the IAB out and use a secondary rod or other implement to verify the up and down movement and measure it.

Next up is opening it up, epoxying your well plugs (which can leak and cause a rich condition), cleaning it and installing new needle/seat/gaskets from a rebuild kit.

 

No, the idle is not changing when I disconnect the TPS or M/C. The dwell is not increasing much if any when I smother the carb. I verified the float level when I cleaned the carb a few weeks ago. I measured the old one and was in spec, installed the new and set it the same. The 2 plugs on the bottom were aleready sealed with something, so I didn't bother them. Another thing I have noticed is that I don't hear the M/C as loud when I turn the ignition ON. I didn't pull the IAB when I cleaned it because it was riveted in from the factory and didn't want to disturb it. I could have messed up the O-ring from cleaning. I hope I didn't screw something up when I cleaned it. I followed the rebuild instructions carefully and didn't have any problems putting it back together. Maybe I should pull it back off and pull the IAB and check those plugs again. It ran for a week fine after I cleaned it and never set a code though. I almost thought I knew what I was doing or something! I don't know what I would do without everyone here's help because I have gone to almost every parts store here and no one has a clue about adjustments on these carburetors or where to get the gauging tools mentioned in the rebuild kits. I was very lucky to find a flex tool that fits the front mixture screws and that's all that I could find here.

 

MC solenoid clicking? Verify travel of the solenoid thru the IAB opening with a small screwdriver or something. You should be able to feel it click up and down and measure the travel. Sometimes one of the primary rods will get hung up and prevent full movement.

How did you reset the lean and rich stop? Your problems could simply be one of adjustment. You've started two turns out (lean) on the mixture screws and gone up to 7 turns out on the IAB?

You can also pop the cover and verify that your needle/seat/float are correctly installed. I've seen the little spring clip come off the needle and hang it up. I once installed the float with the little j shaped hinge in wrong and it flooded the carb. Make sure the j end is in the groove on the pass side.

 

I think that could be a problem too with the rich and lean stop. I didn't change their setings, but don't know how to correctly set them without these special tools the kit keeps mentioning. There was one on top of that little plate over the metering rods and it was 1/8 turn from all the way down. I just put it back like I found it. I don't think my float is causing it, because I'm not flooding or leaking gas, but I could be wrong.
I'm still thinking maybe tonight I will pull the carb back off after measuring the travel like you said and recheck everything. Is there a way to set those rich and lean stops with the top cover off, so I know they are correct before I put it together. I have no tool that will get down in there to adjust the screws on those two adjustments.
I noticed you live in SC, Naf. I am from a little town there called Bamberg. I would be nice if I were still there, I could just bring the carb to you.

 

To set the lean and rich stops correctly you need a special tool. Special tools are also required to adjust them with the airhorn in place. If you reset the top (rich) stop to it's original position you can adjust the bottom stop (lean) to attain 1/8" of travel. Check your travel to confirm but you should be good. You can reset these adjustments with normal tools with the air horn off, just have to place it back on (with a gasket) to measure the travel.

Something else comes to mind. You're reading 45 degrees on the dwell meter. Full lean should show up as 50-52 degrees. The O2 sensor is a narrow band and if the mixture is not within it's band, the ecm will be stuck in the 'last known good' setting for that particular TPS/Vac reading. Your system may not be responding to a rich condition but could be stuck in closed loop because the mixture is too far off for the O2 to respond. This 'last known good' setting could, in your case, be richer than ideal. See the difference?

When you pull the vacuum line open you're getting dwell change and the ecm starts looking at the O2 readings. So leaning the mixture allows it to go into open loop.

Verify your MC travel. Then with your meter hooked up set your idle mixture screws in maybe 1 turn out and lean out the airbleed maybe half a turn at a time to see if you can start getting the dwell to respond. Repeat this with the mixture screws 2 turns out. I wouldn't go past 7 turns out on the idle mixture screws.

If this doesn't bring it in and everything inside checks out you may need to lower your lean stop. This is assuming, of course, that it was not reset back to original position. 4-4-4 is a good rule of thumb for turns out for idle mixture, IAB and lean stop.

When you pull the MC solenoid it's recommended that you count the turns to seat and re-install to the same number of turns out...that is if you don't have the 'special' tool, and who does?

If you were down the road, we'd swap pieces/parts til we knew where we were.

 

I think you're on to something there about the O2 sensor bandwidth. It does take a minute for it to respond when I pull a vacuum line off and then it settles out until I put the vacuum line back on and then it starts going back up and just settles out there. I can't get it to go higher if I smother the carb either. And you know it sure seems like I can't make it stall no matter how many vacuum lines I pull off.
I think for sure now it's got something to do with the travel of the M/C. So if I have to pull the air horn off the carb to be able to set it without the special tools, I might as well take it off the car and on my worktable. The rich screw is the one I can't get to unless I have the tool, even if I take it apart, right? I think I see what you are talking about then. The one that is on top of that little metal plate over the rods is the lean stop, right? I remember putting a mark on the plate and set the screw back to that point after cleaning. I will post back after I get it off. Thanks man!

 

Well, I got it off so I could see things better. I used a rod to stick down in and see how much travel there is and it's barely 1/16" of travel. What screw do I need to adjust to bring it back in?

 

Depends which stop you feel is closest to the factory, original setting. If you didn't make any adjustments to the rich stop in the top of the airhorn then adjust the lean stop to lower the M/C. You can set the airhorn back on with the gasket to measure as you make small adjustments. It's easier if you don't put the booster pump and TPS in while you do this.

For the record (someone else may read this one day): the primary rods go up and down in the jets. When down they restrict flow and lean the mixture, when up the mixture is richer. They're tapered as well so the further down/up the leaner/richer. Therefore the screw that adjusts the lower limit of travel is the LEAN stop. The rich stop is the silver screw in the airhorn. I get them mixed up from time to time myself and have to work it out again in my head.

Something else for the record that I didn't mention before. The O2 sensor only senses the presence/absence of oxygen in the exhaust stream (and only for the odd cylinders where the sensor is). More O2=lean; less O2=rich. A mis-fire will result in more (unburnt) O2 in the exhaust and will read as lean.

Don't mean to come off all-knowing or anything as I'm definitely not.

 

Naf, you are more knowledgable than anyone at any parts store here. Noone here knows nothing about this carb system. I don't know how I would have set this thing back like it should without your help.
It looks like I have found an explanation to what has happened. I pulled it all back apart and found one of the primary rods would sometimes not go all the way down. I looked closer and found that the little clip on the needle had come loose and worked its way into the metering jet all the way near the bottom. Got it out and got lucky, no bent rod or hangup in rod travel. I made a tool out of a flat silver brazing rod and set the lean stop at 1 5/16". This was almost exactly 4 turns out. Checked the float setting. Rebent the little clip to hug the needle a little tighter. I set everything back together without the TPS or accel pump and checked the travel of the M/C plate. I then set the rich screw for 1/8" travel. I found I had to pull the carb back apart once more because after tightening down the airhorn screws the adjustment was a little less than 1/8". This resulted in the rich stop almost all the way to the top. I think the gasket could be a little thin from messing with it, but had nothing to lose at this point so went with it. I set the mixture screws at 2 1/2 turns. I set the IAB valve at 4 turns out. I put it back on and fired it up. Now I hear the M/C clicking again! Yeah! I was so happy I forgot to reset the ECM and went for a drive. Took the car on the same offending flat stretch of road twice and no check engine light! Yeah! Brought it back home and pulled the brake and left in Drive. Hooked up the dwell and was sad to see that it was still stuck at 42. Maybe the O2 cooled down while I was hooking it up? Or maybe from not resetting the ECM or maybe I need to dial in the IAB valve? Either way the car runs much better. It does not have that stumble anymore on first light acceleration. I think I'm almost there. One more thing I noticed this time was that when warmed up and in Drive, I hear the EGR solenoid buzzing. Sounds almost like M/C solenoid, but much faster. Is this normal?

 

Good deal. You'll have to dial it in to get the dwell to respond. One rule of thumb is 3 to 7 turns out on the idle mixture screws, anything less/more and it may be a better idea to readjust the rich/lean stop. Start where you're at and go 1/2 turn out on the screws moving the IAB in and out each time.

EGR shouldn't be buzzing. Have you unplugged it to verify the source?

 

Ok got home from work today and this time reset the ECM before starting the car. Fired up and purred. Went into closed loop pretty quickly. Needle was varying around 42. Couldn't dial it down with the IAB. Turned mixture screws in each 1/2 turn more. This lowered it around 34 and was varying about 6. Then played with the IAB. It is very sensitive now! Wow it works! Dialed it in at exactly 30 with it varying 3 each way. Goes down to 27 and back up to 33. It just keept varying back and forth. I pulled a real small vacuum line and it went up and was varying. I smothered the carb and it went up and started varying. It is very sensitive. I can give it a couple blips of the throttle just enough to squirt fuel from the accel pump and the dwell goes up for a little while and then goes right back down to 30. I noticed it even saw when I put the air filter back on and it went down to 28. I left the charcoal canister plumbing plugged and went for a spin. WOW! Felt a little funny at first, but I guess it was relearning. Took it on a little blast down the interstate and back with a couple WOT to about 80 and was very happy with the performance. Did a little more in town driving and no complaints. Light blips of the throttle sound real peppy almost Mustang-like, not shrimpboat-like, as it was before! I even noticed on the 25 mph stretch home, it engaged the TCC and RPM were down to 1000 and engine was very smooth. So far so good. The EGR buzzing noise is gone without the charcoal canister plumbing hooked up. It was definately coming from the EGR solenoid. I felt it in the solenoid and unplugged it and went away. I will replace all the charcoal canister plumbing and with new fuel line and just to be sure, I'm gonna replace the EGR plumbing with new hard plastic line and rubber boots and see how it drives then. Have to work this weekend too, but should have time to do it. Will let you know how it works out.
Thanks go out to everyone who input on my problem and especially Naf. You da man!