pcopp

Helping son get LG4 Carbureted 305 Idling Correctly

We have rebuilt the motor and installed a comp cams RV cam. Broken in, all start-up/break in issues resolved.

I have rebuilt the CCC Rochester. New TPS solenoid. Have all the Special tools and gauges to setup the carb. Choke works well. Cars starts after one pump on peddle. Secondaries kick in with no bog.

Timing set to 10 degrees BTDC base idle with Dist disconnected.

We just installed complete new AC System. The kicker solenoid is working properly. R4 Compressor is a heavy load when clutch kicks on.

All vacuum lines are new. Stock Air Cleaner with Temp Valve, EGR, EFE and AIR are all removed and carb connections are plugged off. Only systems left on carb are PCV, Bowl VEnt and fuel tank EVAP. New Rochester three way valve and new temperature valve in Manifold for vacuum supply shutoff.

The car runs inconsistently. We set the curb idle and AC kicker solenoid to 750 curb isle with AC on and AC off. Car runs OK. Next day, car idles like crap and wants to stall. Go through the process of adjusting, rinse repeat. Cannot get any consistency day to day.

1. Idle Circuit Screws are 6 turns out (both)
2. Base timing with distributed disconnected - we have varied from 6 to 8 to 10 BTDC. Car idles more smoothly at more advance timing, then we adjust curb isle down to 750 and it is choppy.

I am kind of regretting installing the RV cam. Is this the cause of this inconsistent idle?

Also, I disconnected the EVAP line from carb to cannister and gas was present in the line.

I removed the bowl vents check valve and there was black crystals on the end opposite of the carb. I tried blowing through both ends of the valve and each way passes very minimal flow. I would expect that the carb side should suck easy and the non carb side should be closed (checked off)..

I have the hoses set per the YCN Emission Hose Diagram.

Car is a 5 speed so the choppy idle is a problem at each stop sign/stop light.

Any help is appreciated.

pcopp

erik69&85

iTrader: (1)

The idle screws being 6 turns out is a warning light to me... You start at 2 turns. You may be starving it for fuel. Especially cold when the oxygen sensor is not online yet.

Did you make any changes to the internal rods or jets?.

I upgraded the cam on my lg4 years ago but didn't have these issues... There is a limit.it how far you can go without a custom tube... Especially on the smaller 85 computer.

pcopp

Hello Erik69&85

When I originally rebuilt the carb last spring (wanted to get car running reliable before motor rebuild and new cam breakin), I had set the carb up per the FSM specs (idle air mixtuire screws set three turns out).

Everything seemed OK.

We then disassembled the entire car to rebuild motor, swap rear, rust repair and full suspension overhaul.

Got car back together and broke in cam. debugged everything else, but the curb idle is ******* us.

I only just turned the idle air mixture screws out to 6 turns, as another recommendation on forum from NoEmissions 84T.

His comment:

"If you still have the CCC carb on the car, get the idle mixture screws to 5-7 turns out.
You shouldn't still be at 3 turns."

So I just made the change last week to 6. It did not seem to help much.

I can take it back to 3 easy enough.

Any other ideas why curb idle is choppy?

pcopp

And, the carb has original jets and rods.

NoEmissions84TA

iTrader: (1)

What is your idle vacuum?

erik69&85

iTrader: (1)

Well... When i had a choppy idle on a non CCC quadrajet, the answer was to add idle bypass air since to smooth out the idle I was raising the idle speed up and getting into the off idle slots in the carb. With the additional bypass air, I could close the butterflies and regulate fuel better.

In another case, I had to play with jetting to get better fuel flow. Actually reduced it in that case to smooth the idle.

How far from closed is the idle speed stop screw?.. if it's too far, the off idle ports are active which make controlling the fuel mixture a lot harder.

You may have to play with jetting...trial and error to get it right, especially when cold... Once it's warm and the O2 is online, the computer controls the mix.

Idle mix screws usually end up between 1 and 3 turns with idle speed screws below 1 turn if it's all in balance.

pcopp

So we checked vacuum using the port for the HVAC reservoir.

At curb idle:

Three turns out on both idle mixture screws - vacuum is 17 in Hg
Five turns out on both ims - vacuum is 18 inHg

The exhaust is burning our eyes and smells strong.

We now have another concern.

We were checking timing yesterday again and trying to adjust curb idle without AC and with AC.

We started to hear a clicking noise from the distributor. The rotor came lose from the armature. We confirmed this by removing the cap.

I screwed the rotor back on and the car started right up. However, not the timing light tells us the car wants to run at 40 BTDC at curb idle with the connector connected or disconnected. I confirmed the reading with my light and my buddy's light (both INNOVA Pro).

The car seems to run ok. I cannot believe that the base timing is 40 BTDC.

We removed Plug one and confirmed TDC compression and see the rotor is about 1/2" past Plug #1 when HB timing mark is on 0 degrees so it is clearly advanced.

If we try to retard the timing to lower the base timing the car cannot handle less than 16 deg BTDC.

We did not have this problem before. We are totally lost.

As a final question, we are disconnecting a two wire connector that is left of the brake booster near the Vaccum Pressure Sensor. This is a 1986 LG4 VIN H 305 and it did not have the single wire connector for disabling the electronic timing to the right on the fire wall (I had a C4 Vetter with an L98 and it had the single wire on the right).

Should I be disconnecting the Distributor 4 Pin connector to set base timing?

I am now so confused with what is going on. We are considering pulling the E4ME CCC Carb and ESC distributor and installing a regular Rochester Quad with a vacuum advance distributor that I harvested of a 1979 350 SBC.

Any thoughts on why timing measurement seems unrealistic?

PCOPP

naf

iTrader: (7)

disconnecting the four-pin connector at the base of the dist is the proper way to remove ecm control of the timing to set base.

once re-connected the ecm will add a substantial amount of timing and you'll see near 30 degrees at idle.

however, do not assume that your timing marks are accurate, maybe precise, but not dependable for accuracy. unless you accurately measure piston tdc and make your own mark on the balancer you really can't rely on the timing gun. best maybe to keep advancing the timing until you just get a little surge at low speed cruise with throttle tip in, then back it off a hair.

If the carb's idle air bypass is not providing enough air you'll see a little nozzle drip from the primary venturis when looking down into them at idle. first though, get the timing right then adjust the carb for proper dwell.

6 turns out on the idle mixture screws isn't necessarily a bad thing. too much fuel there can be compensated for less idle air at the Idle Air Bleed adjustment screw. you do want to avoid a situation where you're too many turns out on the idle mixture screws and too few turns out on the IAB. with a varying dwell of 50% you kind of want each centered around 4 turns out.

if you're running rich now it's likely your ecm isn't seeing a valid O2 reading and the dwell is 'stuck' in a rich condition.

best to disconnect EVERY vac line from the carb and manifold when setting dwell. Get it right then re-connect one at a time. any problem line will show itself.

I've installed that cam or a similar one in a couple LG4s. Idle had just a hair of chop to it but it was well mannered.

pcopp

Hello NAF,

So I used a degree wheel to verify the cam card and it worked out that the mid point between 50 mils BTDC and 50 mils ATDC put the harmonic balance factory mark on zero on the timing cover. HB is new so I am not concerned it slipped. So I believe my HB/Timing mark are accurate for ZERO TDC.

So if I understand correctly, should I take every vacuum line off the carb (including the PCV Valve, power brake, HVAC reservoir on manifold and the Choke dashpot) to set the base timing with the 4 pin disconnected?

I will proceed as follows:

1. Remove all vacuum lines and disconnect 4 pin.
2. Start with idle mixture screws at 3 turns out (per rebuild instructions)
3. Check/set timing to something reasonable (hopefully 8 to 12 BTDC like I was getting before
4. If I get past that point, reconnect the 4 pin and start adding vacuum connections one at a time and see how curb idle responds.
5. If I get everything back on, then I will reconfirm the TPS voltage and the MCS dwell.

I will message back with results.

What is your thought on the 15" HG vac on the manifold with 3 turns out (normal, low??)

Thanks again.

naf

iTrader: (7)

if you're confirmed your timing set base at 0-4 degrees advanced with the four pin connector disconnected

reconnect the ecm control (you can always bump the timing up more later)

get dwell to near 50% and varying with all the vacuum lines disconnected and the ports plugged. Adjust your IAB to set dwell, idle mixture screws if needed.

Once the dwell is happy reconnect you vacuum lines and note any that cause a change in dwell.