street_carnage

first off, im no carb guy and i have a lot to learn about vacuum advance, timing blah blah, i know the basics but here goes. thx for reading my long post.

1. attached is a pic of my carb and dist. am i computer controlled?
2. when i put my intake manifold on last year i brought it to my old mechanic for some work and he says "ah i like how you plumbed it for manifold vacuum" i dont know how i should set it up, ported or manifold.
when he said that it left me thinking its supposed to be ported vacuum. he also talked about open loop and closed loop and im thinking what the f***??
(i had an idea somewhat of what the difference is but i cant remember anymore.

my problems are this..
crappy idle. period.
1.hot or cold, when i punch the gas in neutral and back down. it will try to stall out.
2.or when i drive and brake for a stop, it will try to stall with the clutch in.
3.if i kick sideways or even a burnout then brake for example, it will bog out and then struggle to start up. (all these relate to problem #1)
4.sometimes it will diesel on me, today it actually backfired, that sucked
5.sometimes the throttle will stick open at like 2500 rpm, while driving, that sucks, usually i can kick it back down, but sometimes it doesnt work.

it used to run great, until i changed the intake and took my carb adjustments to a crappy mechanic. im thinking vacuum problems, and in need of idle mixture. and maybe some igniton problems. last tune up was about 20,000-30,000 kms ago, that was like 3 years. its been parked for a while. chances are the gas in there is garbage too. i think the first step is to burn that off clean with an additive of some sort.

dont tell me to get a new carb or bring it to someone. i really want to learn more about vacuum and quadrajet adjustments. just need a walkthrough, step by step. i cant find anything on the boards and i think it would be very useful to alot of people.

im not an idiot btw, ive just never understood vacuum advance, timing and how to set it up good or proper carb tuning. i'll be really happy if somebody can help me fix this and tune it good. pics on the way.

street_carnage

the first pic shows the dist and driver side of the carb, i was told to look for the diaphragm on the dist. i was told if it was there it is non cc

the second shows the top of my carb after sitting for 3 hrs.

the third shows the driver side of the carb.

on the pass side i replaced the check valve on the power brake booster but not the black thing inbetween.

street_carnage

the first here shows a fuzzy closeup of a concerning point. the guy who set my carb up disconnected that green plug coming from the greenish wire from the carb. said it would run better

the second of the whole engine shows the whole motor in general, to see if theres anything you can pick or point out. notice the green wire from the carb unplugged also that green plug on the top of the thermostat housing is unplugged.

can you tell what kind of vacuum im set up for. manifold or ported.
ill take certain angle pics if requested.
hope someone can help...

street_carnage

also, the car sat for 3 months and the first startup there was constant smoke coming out from the exhaust manifold heat riser on the pass. side of the motor. is that normal.

Angelis83LT

first.. on the thirdgens.. many of the early ones had a vac advance and were computer controlled. All three of mine for instance... second.. your IS computer controlled.. just look at the carb.. see them wires going to the carb and the plugs plugging into it.. only a Computer Controlled Carb will have that. And can't really tell by those pics where you have the vac at.... tis a big mess lol..

xpndbl3

iTrader: (5)

computer controlled carbs shouldn't have a vacuum can, the timing advance should be added by the computer.

street_carnage

so is it cc or not, it has the can on the dist and the wires on the carb. it is a canadian lg4, there not supposed to be computer controlled.

Angelis83LT

i dunno about that. Even my Stock 84 z28 HO car has that vac can on it along with all the computer controls... so i guess that is not really a sure fire way to check.. reguardless your carb has the connections on it for the computer controls.... so it IS computer controlled

street_carnage

on the first pic you can see the efe (low can under the driver side, exh. manifold) isnt connected to anything.

second pic is a decent view of the vacuum hosing. the egr and efe tvs looks weird either im missing a bunch of stuff. also there is to lines on the carb that are plugged off. i have schematics for a non cc.carb, but if i am cc, is there a routing diagram for that.

naf

iTrader: (7)

That puppy IS NOT computer controlled. The two wire connector going to the carb is for the cold start solenoid (proper name?- my book's been loaned out) that provides an additional booster shot in cold weather. There is no throttle position sensor (three wire) plug on the driver's side front.

Your EFE (early fuel evaporation) valve on the pass side manifold is provided vaccuum through the vaccuum temp switch on the water neck that is not connected. When cold the valve shuts to route exhaust gas from that side through passages in the intake manifold to warm incoming air/fuel.

Is the green wire one of the wires connected to the solenoid on top of the carb? Maybe it grounded (if the other wire is hot) through the thermal switch on the water neck? If the switch was bad or it was otherwise constantly grounded it would provide too much fuel when hot and that may be why he disconnected it?

I've read about those mystery canadian carburetors but never played with one. Guy named Sonix could probably help.

Apeiron

It's a typical Canadian LG4, not computer controlled.

Apeiron

If your distributor has a vacuum advance can on an L69, it's not stock.

Sonix

iTrader: (1)

whoa, I can see how you might be getting confused from this advice here
(street_carnage pm'ed me to check this thread, in case i'm stepping on any toes here)

-1st, Apeiron is right, *most* 3rd gens with LG4's came to canada non computer controlled. Mine was computer controlled however, so that's why I say most

-A computer controlled carb has 2 plugs on it (aside from choke), the mixture control solenoid on top, and the TPS on the front. Yours only has 1, on top. It's very similar to the mixture control solenoid, but it's a "cold enrichment" addition, usually used on trucks. I didn't know 3rd gens ever had that stock. I'm not sure how the computer controls this.

-You have a vacuum can on your dist, so it's not computer controlled. Seems like everything matches.

-I fear electronics (on cars, not in other places), so I try to avoid them if I don't know what they do. The stuff on your water neck, is probably the "cold" sensor, and has to do with the cold enrichment on the carb. Like I said, I don't know how that works. Chilliwack is pretty similar to vancouver in climate i'd guess (i'm from Vernon...), so I don't think that's all that necessary. If I was in your shoes i'd find a q-jet without that enrichment, and get a normal waterneck (the $12 chrome guys from c-tire with the 45* angle on it). Or else look into how that enrichment works (not what i'd do, but you can pick your poison).

FWIW - I used a dist, and carb, from an '84 cutlass at the wreckers. Good shape, covered in grease, but un-screwed-with. It worked well on my LG4, and works well on my medium 350 now.

advance - ported advance gives you a linear advance curve from the vacuum can. Sorta. As you open the throttle more, the vacuum port on the carb gets to see more of the signal (now that the butterflies are "showing it" the signal, so it comes on, basically linearly, with respect to your throttle position. Got a vacuum gauge? ($30 at c-tire, you need one). Hook it up to random ports on the carb and find out which are which. The one showing 0-1" at idle is the ported ones. ok, so the vacuum (and therefore the advance, if you've got it hooked up to your distributor advance can), will come on linearly, until somewhere near 50% throttle say, then it'll be identical to manifold vacuum advance. At WOT, both show 0.
manifold is a lot more boring, it shows the actual vacuum that the engine is making. until WOT, where it drops to 0.
ok, to sum up for vacuum advance - manifold timing gives you +~20* timing at idle, if you have a HOT cam you may want this, a stock cam - you don't. I'd stick with ported vacuum advance. Once you start messing with the motor, you can pick and choose.

that's my post on information, as far as "what do I do now?", i'll reply later this afternoon. I'm at school and i'm hungry . hunger trumps you.

Sonix

iTrader: (1)

forgot to add my sig, in case you were curious.

Sonix

iTrader: (1)

oh yea, open loop vs closed loop is more of a fuel injection thing. I think a ccc carb *might* do that... I wouldn't worry about it.

I'd burn through that tank of gas you have now first. Then fill up with some decent quality 87 octane. Maybe some seafoam in the tank too. Check all your vacuum lines for cracks or age, maybe replace 'em if you want to as well. Check all other fluids of course too.

Check your timing. I'd recommend getting the crane 996001 vacuum advance can. I think it was $50 at c-tire or mopac (lordco near you?). That's a highly adjustable vacuum can, rate and amount, as well it comes with the springs for your mechanical advance. I'd use a light and medium spring to start, then disco the vac advance, plug the line, hold the engine at 3000RPM (after it's warmed up), and set timing to ~34*. Then hook up vacuum to a ported source (that was stock for your motor, so it should work just as well now). Re adjust idle speed to your liking, and adjust your idle mixture screws (if there are no caps on them).

and maybe check your plugs, regap or replace.
Check if your passenger side valve cover gasket is cracked and leaking, that could explain the smoke.

That's your basic tune up there. Maybe a cap and rotor if you think it's about time. If it still runs poorly i'd say to rebuild the carb, and probably go to a non-enrichment setup.
Lemme know how it goes.

five7kid

iTrader: (14)

The computer doesn't control the cold enrichment. It's a thermal switch. I was under the impression all non-CC Canadian 3rd gens had it. But, likewise, no personal exposure.

You don't necessarily need the stock thermal/vacuum switch for the vacuum advance. It's an emissions thing; for good operation all you need to do is connect the distributor advance can to the timed/ported vacuum port.

FWIW: I have an '84 full-sized van the originally came with an LG4 and TH700. It has a computer, it has a large-cap distributor, the distributor has vacuum and mechanical advance, the distributor has both the "normal" large-cap distributor wires to the cap plus the flat 4-wire connector coming out of the base. The carb is not computer controlled. When we got the van back in 1996 the engine had been replaced by a dealer with a Goodwrench 350 using all of the LG4 equipment, the flat 4-wire connector was disconnected and two of the wires on the chassis side had been jumpered together. When I disconnected the jumper, the engine stopped. Plugged in the connector w/o the jumper, and it's been running fine that way ever since. Weird setup, I don't have any idea what the computer does, but it must do something because it won't run disconnected (like you do to set the timing on a normal CC set-up).

naf

iTrader: (7)

"oh yea, open loop vs closed loop is more of a fuel injection thing. I think a ccc carb *might* do that... I wouldn't worry about it."

The ccc-qjet actually has three modes. Open loop/warm up/full rich; Closed loop ECM uses TPS/BARO (ecm doesn't look at O2) and Closed loop TPS/BARO/O2 (O2 readings are overwriting MCS cycle data). Not really pertinent here but worth knowing (IMO).

Sonix

iTrader: (1)

ah, thank you both for the corrections.

naf

iTrader: (7)

Corrections heck, it took me a day and a half to figure cubic feet per hour natural gas from input British Thermal Units/hour (that was this morning). You ME guys live the life.

Oh yeah, wish I had a full size fan...er.. maybe not.

street_carnage

thanks for showing up sonix, heres what ill do to start. im gonna go to lordco, grab several feet of vacuum hosing. replace all the lines. and plumb it like this. then ill tackle all the timing and adjustments. good?
the only problem is i dont have the thermac air cleaner anymore as you see in the pics. i have that hard line on the back of the carb straight going to the power brake booster.

thanks for all your input guys, it'll be a couple days before my next post , im stuck at work and have no time. (prep for car going in to the body shop for paint. im putting a all new interior in, the rear end was just redone still have to break it in. but ill most likely be setting up the timing and the carb in a few days, just have to run the DA over the body get all the crap off of it. and finish laying interior panels. after all this, tackling door rattles, doing the TDS hinge repair kit. hope everyone sticks around to help me with the carb and timing. this board rocks

Sonix

iTrader: (1)

wow that's one complicated mess there. Sure, I guess that'll work, assuming all those parts are still working ok.

yea, your hardline at the back of the carb to the brakes is normal. It's not shown in that diagram actually. The diagram is meaning that small nipple next to the threaded fitting on the back of the carb. And yea, I wouldn't worry about it not having the thermac.
*However*, the TRIANGLE OF DEATH also isn't your best choice. Do a search on that if you want to know more.

oh, lemme know how that TDS setup goes, i'm going to have to do that sometime.

Sonix

iTrader: (1)

ha! If you say so... you can take my place in my "mechanics of materials II" anytime... Do a google on the "Levi-cevita" symbol, "tensor product" in index notation and "the Kroenecker delta".... You'll want to gouge your eyes with a SHARPENED SPOON@!

I have no idea why you're talking about a fullsize fan though.

Fast355

iTrader: (2)

That carb looks to be essentially the same as the 1985 and 1986 truck carbs in the US. They had a Dual Capacity Accelerator pump, which used a solenoid in the typical MCS location, which grounded through a thermal switch on the water neck. A cold engine recieved roughly 50% more pumpshot than a warm one. Really just a way of leaning out the choke settings and idle mixture for less emissions.

Fast355

iTrader: (2)

five7-
The engine in your van should have been the LE9, it was more like the L69 than the LG4. The Distributer in your G-series truck engine is just a standard old HEI, but with a 5 pin module installed. The 5 pin module sends the distributer reference pulse to the ESC module under the driverseat. The ESC module is a simple analog controller without a memory of any kind. Very basic, not like the ECMs. Under normal situations, the distributer reference pulse was returned back to the ignition control module, unmodified. The 305 had a knock sensor in the passenger side block drain. When detonation was sensed, the ESC module "ALTERED" or delayed the timing signal back to the ignition control module in order to retard the timing. The ESC module would retard the timing until it stopped knocking or hit the electronic limit (around 10* or so). A vacuum switch was mounted on the firewall and closed on rapid vacuum decreases, such as stomping on the gas. This would retard the timing roughly 5-10* depending on the duration of time the switch was closed, which depended on the amount of vacuum change. This helps eliminate tip-in pinging that would otherwise occur. The system works very well on a 350 when used with a 350 knock sensor. The actual distributer can be re-curved just like any standard HEI, due to the WEAK timing curves used in it and the heavy reliance on vacuum advance, I highly recomeend doing this. Eliminates the weak feeling @ WOT that this system gives in stock form.

street_carnage

hehe, the triangle of death caught on fire while adjusting. it dieseled on me again, backfired. started smoking bad, and melted after i pulled it off. good thing i was standing there, im gonna head to lordco and get an open element air cleaner.

can somebody look at the diagram pic and then to my carb pic and tell me if im missing vacuum ports on the intake or something. im confused, on the diagram, it shows EGR TVS, EVE TVS, and TVS. with 2 ports on the egr TVS and efe TVS, and one the TVS. where all as i have is the one thermo housing with 2 ports and one big 4 port connector directly on my manifold.

what is the best fluid to spray to check for vac. leaks.

street_carnage

hey sonix, i want to see a pic of your intake and carb and how you routed your vac. hosing. do you have one?

five7kid

iTrader: (14)

At least 2 of them are plugged off in your pics. The others look like they have hoses on them already.

street_carnage

but everything on the mainifold that should be there is present right

Sonix

iTrader: (1)

This is pretty much what it looked like with the LG4.
https://webdisk.ucalgary.ca/~jmknopp..._html/carb.jpg

https://webdisk.ucalgary.ca/~jmknopp...ac%20port2.jpg

https://webdisk.ucalgary.ca/~jmknopp...ac%20ports.jpg

and now it's more like this:
https://webdisk.ucalgary.ca/~jmknopp...ay%20may06.jpg
I don't have any detailed pictures of it now. But it's a pretty simple vac hose routing now - just power brakes and distributor advance are used, along with PCV.

haha, so the triangle of death lived up to it's name

My LG4 vac setup also didn't use much. Most of the accessories were AWOL, or broken, so I left them disco'd. You don't need much to have the car run ok.


starter fluid works, I think wd-40 even works... I use a propane bottle, like the plumbers soldering style one... *unlit*

xjcamaro89

I noticed you dont have a hose going to the charcoal canister, do you need one?

street_carnage

there is a hose going to it