How exactly does the thing work?

It seems like it has like 3-4 stages. 1750RPM, I hit it down as soon as I start th engine to 1500. As the engine warms up it goes back up to 1750, I kick it back down and it falls to 1250. It warms up more and goes to 1500, I kick it down and it goes to 1000. I kick down again and finally its normal idle.

Now, my buddy said that when I go to the gas station or such, don't pump gas, just start the car up to bypass the choke. But when I do that, as soon as I hit the gas to accelerate, the choke goes into the final stage and the engine revs up to like 1100RPM. It won't drop out instantly either, wants like 45 seconds to drop out. Is it just the electricty that heats up the spring inside? Like...the choke isn't affected by engine temperature, just by the electricity heating the wire up?

Also, I'm getting like 10MPG . I filled the tank up, I went 45 miles on about 3/8 of a tank. Thats pretty bad to use over a 1/4 to drive 45 miles, especially when the guy at the station topped it off with an extra 1/2 gallon to make it an even 13.00$.

I just dont' know what to do, the engine is running good. Starts right up, clean throughout the entire powerband. Smooth idle, good part throttle, good WOT, just no gas milage. Currently the car is set up running off of FULL engine vacuum, not ported. Is that hurting me? I was getting like 9MPG with it set up using the ported vacuum before, then again, the car was like 4-6 degrees retarded and deiseling at that point. I dunno if I'm just stuck with a 10MPG engine, just doesn't make sense, my cam isn't that aggressive, are the vortec heads just sucking in that much extra air/fuel.


Thanks,
Dave

 

i had that exact problem before with my 3rd gen and the cause was due to the choke heater wire coming disconnected. make sure the wire is connected to the choke heater and that it is getting voltage. without voltage to the choke heater, the choke will not totally open causing the poor gas mileage. since the choke isn't fully opening, the linkage will not come off of the fast idle cam, which is causing the fast idle when the engine has warmed up.

if this isn't the problem, i don't know what to tell you. i'll have to think about this one some more.

 

Well it does drop out of choke after a while. When I came home from work 10 minutes ago I went inside and when my sister left I went back outside and put my car in her spot. I didn't pump the gas, the car was only sitting like 5 minutes, the second I hit the gas to give it a little go, the choke went into final stage and was reving about 1100. It's just annoying, I guess thats normal.

I filled the tank back up, after 54 miles of driving the car took 6.96 gallons of gas. Thats 7.7 MPG....so I don't know what is wrong. I figure it has to be the carb or still a timing problem. Car starts right up and runs smooth, but it doesn't seem to have any power. Maybe still a timing problem.

 

I have a Performer 600...and I've got the same goddamn problem. Hoping someone will respond and give some advice...

Part of my problem was the choke wasn't grounded out enough... giving it a better ground helped it, slightly.

 

The street avenger came grounded to itself I think. I only had to plug 12v power to it and it started to work. I think right now, it's just because I've never had a carbed car before and I just didn't know what to expect. I just thought that even though my car only sat for like 5 minutes that the choke shouldn't come back on so fast. It's annoying. But normal I guess.


The fuel milage is whats annoying me now.

 

Oh, sorry. Just read the "edelbrock performer" thing in your sig.

Damn man, good luck. I replaced my quadrajet with my performer, and my fuel economy took a 6 MPG dump and they're tuned identical. I have no idea what the hell is the matter with it... heh. Was waiting til summer to deal with it, but would be nice if someone here had a good answer.

 

The most important thing with a choke is that IT OPEN ALL THE WAY WHEN THE ENGINE IS WARMED UP. When cold it will close all the way and elevate the idle speed. The Qjet has 3 idle speeds. High idle (cold engine, choke fully closed), intermediate idle speed (when the choke is about 3/4-1/4 closed) and then low idle (whsen the choke is fully open) which is adjusted by the normal curb idle speed screw on the driver's side of the carb. The two higher idle speeds are kicked in by a "high idle cam" that is part of the choke linkage on a Qjet.

The choke should be FULLY open in about 5-6 minutes after starting it "overnight cold". Take off the air cleaner lid and verify this- the choke plate over the primary throttle bores should be FULLY open. If the choke isn't getting fully open your idle speed can be elevated and fuel economy will suffer considerably.

Old Qjet choke elements sometimes go bad and won't heat up fully or open fully. Like was said above, the first thing to check is to make sure you're getting a full 12V to the choke ANY time the engine is running. Check it at the wire that plugs into the choke element. Check ti while it's actually connected to the choke- sometimes the choke element is fine but the wire supplying voltage to it is "weak" and won't hold voltage while under the load of the choke heater.

Yes, the choke element in a late-model QJet is basically a temerature-sensitive bi-metal spring heated by an electrical heater which is fed power by the choke wire. It's only one wire on a Qjet (the ground is supplied through the body of the carb itself).

 

Stealthelephant - the choke shouldn't come back on after the car has only sat for 5 minutes and should be getting way better than 8 mpg. i don't have much experience with Holley's (my 3rd gen has a 600 performer on it), but you should be able to adjust how long the choke stays on by rotating the choke heater housing. your instructions should tell you which way to turn it. if you are absolutely sure that the choke is working correctly, its all in the jetting. do what Damon suggested and verify that the choke is fully opening after about 5 min.

KnightRider350 - how do you know that the performer is setup exactly the same as your q-jet? you shouldn't have experienced any loss in mpg unless you motor is still computer controled.

my 3rd gen has a 350 hp small block (.060 over, ported 305 heads, mild cam, 600 performer, RPM manifold, headers, 3" single exhaust), 700r4, and 3.73 gears. it gets 22 mpg on the interstate, 19 on two lane highways, 16 around town, and 14 pulling my dirtbike on a small trailer. i don't know what kind of head/cam/intake you all are running, but you should be getting twice the mileage you are seeing.

 

Ahhh...I finally got some answers today.

Basically, I have too much compression to run vacuum advance with my setup. I have to run like 16* initial, no vacuum advance, and then get about 34-36 total advance with mechanical. So I'll have to adjust the weights since my distributor has 24* mechanical advance from the factory. That was my problem.

 

never heard that one before. my sbc has 11:1 and i run vacumm advance.

 

What cam are you running?

I trust the guy, 45 years of building race engines, he knew exactly what was happening when I told him my problem.

 

i didn't mean to come off sounding like i was doubting your source of information. i guess i don't know enough about your setup. after i thought about it for a few minutes, i'm guessing that you where gettting alot of detonation and had to take alot of base timing out of it to eliminate the knock. where did you have the base timing set at?

is this a street car, or mainly a strip car? you may want to try an adjustable vacuum advance canister. if you can get the vacuum advance to work, it will make a big difference on driveability and economy on the street. i would recommend the Crane Cams adjustable canister. it also comes with springs to adjust the mechanical advance. good luck.

 

Well everyone I talked to told me I needed to run a higher then normal intial advance. Like 12-16* as opposed to 8-12*.

So I went to the guys shop (I buy all my parts through him) and told him my problems. Basically, he said that with my compression I was going to have to run timing around 16*, and that the vacuum advance was what was killing me. That I would have to run full mechanical advance or, as you said, run a vacuum can. Now the guy who helped me build my engine, wants to simply adjust the mechanical weights, and he was saying something about checking total advance with the timing light. And setting exactly where I get total advance etc etc. Now my distributor manual says that I get 10* of advance a@ 10" WC of vacuum, and that it's adjustable. I don't know what the plan is, but it makes sense.

The car felt like it had the most power from 2500RPM+ when I was running 8-10* base timing, but I had very poor idle, very bad response under 1500RPM, and it was deiseling every now and then. With base timing around 14* I get pinging @ WOT around 2500RPM. From what I've been told, I can't run 14-16* of intial advance and have 24* mechanical, because combined with my compression, that much total advance at WOT is going to hurt me. Then again, I can't run the engine down low with intial because it just doesn't seem to run right. I dont' know, I'm new to all this, I'm learning every step on the way.

 

definately check your over all mechanical advance with a dial back timing light or put a degree stip on your balancer.

for an example, i'll give you my setup.
base: 12 deg.
overall mechancial: 32 deg
max vacuum advance: +25deg @ 13 in.
vacuum advance start: 9 in.

bascially, i took out some mechanical advance from the stock hei by changing the springs and using the stock weights. i limited the overall vacuum advance and cranked in the spring so that pretty much all vacuum advance is out on medium to high load throttle positions.

it sounds like you have good fellas helping you out. be patient, it takes a far amount of trial and error to get it right. i still think that there is something else wrong besides the timing.