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.
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The link you posted looks different than the sensor I have on my water neck. I'll try to snap a picture of mine when i get back home today. But mine looks alot like a 1 wire fan switch, only it's not since I've got a mechanical fan, and it has 2 wires going to it.
CTS shorted to ground? A routine diagnostic test for the CTS is to short the leads to each other. This 'fools' the ecm into thinking the engine is running at temp. I've done this countless times and never pulled a code. 'Course most tests would be done at idle so tripping the code may require other things to be present.
The two wire pigtail for the CTS can be picked up at most parts stores. I see them at AZ in the electrical stuff aisle. Next to the receptacles for trailer hitches.
A change in idle quality when the CTS plug is removed indicates the motor may be going into open loop although we still don't know for sure that it's seeing O2 readings. The lack of lockup indicates lack of closed loop but VSS could cause this.
Okay well what all would you like me to take photos of? The CTS was shorting to the other wire that was connected to it which tripped a code when I was cruising to the parts store earlier. I reset the codes and separated the wires from one another a little bit and drove a good 60 miles and the Check engine light never came back on. One reason I'm thinking that the VSS might have died on me is that the cruise control did work when i got the car but about a week ago it just went out randomly.
I like to adjust the timing first prior to any other adjustments. I recommend starting at zero degrees for the LG4. I've tried 4-6 degrees advanced and noticed driveability issues such as light pinging, surging under decel (while converter is locked) and loss of mileage with more advance. 'Course these symptoms may be specific to my Pontiac as it's the only 'stock' LG4 I've driven regularly.
After setting timing and reconnecting the EST it's always a good idea to verify timing advance with the light. Not important to tell how much, necessarily, but just verify that it is advancing properly.
Before moving to dwell it's a good idea to check the TPS voltage. Backprobe pins B and C (middle and bottom if memory serves) with ignition on/engine off. At idle throttle setting you should have close to 0.40 volts and it should go up to around 4.0 volts with throttle completely open. Just need to be close now as idle throttle position may later change and the TPS can be fine tuned then.
I like to plug every vacuum port on the carb and manifold except the vac sensor line to the rear before proceeding. This allows you to eliminate most of the possible vacuum leaks and after setting dwell you can reconnect each one and verify with the meter that none are leaking.
It's a good idea early on to verify that you have 1/8" of free movement of the MCS plunger inside the carb. I've seen them get hung up and such. To do this remove the IAB after first counting the number of turns to seat it so you can reinstall at the same height. Use a small rod or some such (I usually use a secondary metering rod since they're always handy in the little plastic tub of my carb parts where that little ruler is). Use the rod to verify that the MCS is clicking up and down and measure its travel. If the MCS isn't moving or out of 1/8 " get back with me as the carb needs to be opened.
Connect the dwell meter to the green, single wire diagnostic lead near the fender/firewall by the blower motor. Connect the ground lead to any convenient ground. With the engine running and fully warmed up the dwell should 'hover' around 30 degrees on the six cylinder scale. If it stays rock steady, most likely the engine is not fully warm, O2 sensor is not hot enough or the carb is out of self-adjustment range. An engine with headers may have trouble keeping the O2 sensor warm at idle-I use a heated O2 for my Camaro with hedders.
If the dwell meter reading is ranging and it responds to choking the air horn (with a rag) by increasing but is not centered on 30 degrees at idle, slight adjustments to the Idle Air Bleed (IAB) are required. Turning the IAB out will allow more air in and lean the mixture causing dwell to respond by dropping. The reverse is true.
The dwell reading indicates the amount of cycle time that the primary rods are down in the jets restricting fuel. More dwell=leaner; less dwell=richer. Adjustments to IAB should be done in small increments (1/8 turn) and a few moments should be allowed after each adjustment to allow the ecm to correct the mixture.
If the dwell is rock steady at some setting (usually between 10 and 50 degrees), it could be stuck in its 'last known good' setting because the O2 readings are too far out of range for the ecm to adjust to. First pull the connector from the CTS and ground the leads to each other, this will confuse the ecm into thinking the engine is at temp and will rule out a bad CTS. If no change continue with:
Turn in both idle mixture screws on the base counting number of turns. Set them both out at 2 1/2 turns. Set the IAB at about 3 turns out. With dwell meter connected turn the IAB out in small increments until it's about 7 turns out. Stop when the dwell begins to 'range' and respond to changes in IAB. Set IAB so dwell hovers around 30.
If dwell does not respond by the time you get 7 turns out on the IAB repeat this process starting with 3 turns out on the mixture screws. Repeat by adding another 1/2 turn to the idle mixture screws. Ideally you want to be between 3-5 on both. If you go more than 7 turns out on the mixture screws your carb may require adjustment of rich and lean stops.
Once you get it set on the sweet spot, set your curb idle at 500-600 rpm and adjust the TPS to read close to 0.40 volts at curb idle setting (it may be a little finicky and not exact).
If your carb is re-built all of these set screws should be visible. A carb that's never been touched will have plugs and or covers riveted over some of these adjustment screws. It will also be more than 20 years old and likely need a re-build anyway.
Reconnect each vacuum line one at a time and look for a change in dwell. The dwell will respond to a vacuum leak by decreasing (richening the mixture). If this happens with one of the lines, fix the vacuum leak.
Put your dwell meter on the carb every six months or so and you can use it to check for proper operation of the sensors and vacuum leaks. When everything was new you could go years without having to worry about component failure, not the case any more.
I'm going to take some pics the next day that it's not pouring down rain here to make sure we're talking about the same thing for the CTS. I've also got more check engine codes that tripped. Now I've gotta look up what they are. And the list is in the car. There were the 2 I had before that still came up and 2 new ones. The only thing I did was unhook the not working air system and remove it, and reroute a few vacuum lines. Maybe the vacuum lines tripped a code. I dunno, i guess we shall see.
There are some pics of what I'm pretty sure is my CTS. It's right on the top of the water neck. And I checked the codes one was a code 33 Map - Volts hi/vac lo, the other was a code 23 - M/C solenoid open or ground. Now the map sensor one seems pretty straight forward, I need to find a vacuum leak. But what is the M/C solenoid? And where's it at?
That was the CTS. You need another one. I got one at O'Reilly's once that included the pigtail. MCS is in the carb body. Code may have set when the connector was off. Clear your codes and see if it trips again.
Okay new question. How do I turn up my idle? it's realllly low, and kinda stumbles a bit between 300 to 500 rpm when at op. temp in drive. Sometimes stalls out completely.
Okay new question. How do I turn up my idle? it's realllly low, and kinda stumbles a bit between 300 to 500 rpm when at op. temp in drive. Sometimes stalls out completely.
Put the E brake on and something in front of the tires if needed and then put the car in drive. The idle screw is on the drivers side. I attached a pic with it circled. I would set it at 6-650rpms. turn it to the right to up it. make sure you do it with the car in drive and be careful while in front of the car.
Only real problem with that is that I don't have a working E-brake. Anyways I did find that screw yesterday after i posted and adjusted it up. hasn't stalled on me since, and the stumbling has seemed to go away.
Figure 6C1-21 shows all the parts, the MCS is #63. The connector is held down by #62, so look for that to see what the connector looks like. It sits in the top front passenger corner of the carb. You can see it in the pic camaropunk posted. If there isn't a 2-wire connector hooked up to yours right now, you've got a problem.
The connectors visible in your photos don't look to be in good shape. They use "weatherpack" connectors for these harnesses for a reason. If the connectors are FUBAR, get them replaced.
Yeah pretty sure I've got one of those. Exact position that you said it should be in. And mine does have a connector on it. The clip part is broken but it's always stayed in just fine. Maybe it did come loose once when driving it's always a possibility. So a new connector would be a good idea if I can find a place to get one.
Also when that MCS is plugged something in my engine compartment makes an annoying clicking noise. Is this normal?
I would imagine thats what it's coming from because when I take the plug off it the noise stops. I think the noise only is there sometimes at idle and when i turn the key to the "run" position before I start it up.
Oh and I got a timing light, but on the timing tab, what one marks how much advance i should actually have? like I started playing with it, and it appears as if my car was retardedly advanced. But then it occured to me that I could figure out with mark I was lineing it up with. So i put the tools away for the night.
You have to disconnect the flat 4-wire connector going from the base of the distributor to the firewall harness before you check the timing. If you check it with that connector still connected, the timing mark will probably be off the timing tab.
The bottom of the biggest "V" in the timing tab is the "zero" mark. Every small mark to the left (from the front of the car facing the engine) is 2 degrees advanced (there are two "small marks" for every small "V" on the timing tab). So, if you want 6 degrees of "base" advanced timing (with the 4-wire connector disconnected), you set it so the light flashes on the 3rd mark to the left of "zero" at idle.
I would imagine thats what it's coming from because when I take the plug off it the noise stops. I think the noise only is there sometimes at idle and when i turn the key to the "run" position before I start it up.
If you took the connector off the MCS with the motor running it will trip the code 23 you got. Hopefully that's what it was.
