I am having trouble with my 4 barrel carb. It is not running on its secondaries so I am not getting full power when driving or even while I'm parked. Should the secondaries on my 4 barrel carb open up while revving it up while I'm parked or no? Maybe it's a vacuum problem or something I don't know someone help!

 

No the secondaries should not, and will not open when you just free rev the engine. Engine must be under a load (driving on road, or on a dyno) before they will open.

What kind of carb do you have?

 

I believe I have a holly carb I think that's what my father told me, I'll know for sure later today but I'm pretty sure that's what it is. And even when I'm driving they don't feel like they're opening up it feels as though I'm only running in half the engine. I should be thrown back in my seat when im driving this monster but I'm not at all!

 

Check your vacuum lines, make sure there isn't a leak somewhere. If it has mechanical secondaries you may have to take a look into the carb.

 

It is a mechanical secondary. We've checked the vacuum lines but we'll keep checking them out. I'm gonna get my carb adjusted soon at the mechanics and maybe they'll see if there's a problem with the secondaries mechanically unless there's a way for me to do it? I duno lol

 

Can you post a picture of your engine/carb? That will help out alot.

You should feel and hear the sec. open while driving but by no means should it "throw you back in the seat" unless it's a high performance engine. Stock or mild build will NOT give you that feel.

This also sounds like it could be other tuning probs other than carb as well. Like timing not set right, TV/detent cable not adjusted right, etc

 

okay well here is my carb, let me know if you need to see anything else!

 

That's not a holley.

That's a Rochester Quadrajet (Known as a Qjet), also it's an electronic version of the Qjet (known as the E Q Jet or E Quadrajet, as well as CCC *computer controlled carb* ) which was used during the very late 70's through mid 80's from GM

That carb has vac/air valve secondaries, not mechanical.

Here is a write up on rebuilding one and has lots of pictures and info http://www.hotrod.com/how-to/engine/...retor-rebuild/

Change your fuel filter, they are small and clog easy and see if that helps your prob. The fuel filter is inside the carb. Look at where your rubber fuel line goes on front of carb. There is a small nut and a big nut. The fuel filter is behind that big nut.

 

Okay I'll change the fuel filter. How much is a new one exactly and is it easy to change? Like I won't have to do it myself or should I just get the carb adjusted and tell them to do that as well?

 

Do it yourself... The filter will be cheap. $2.59, $2.99, $3.29 price range

We all start somewhere. Today you learn how to change a Qjet fuel filter, which is the 1st step to learning all about cars and engines. The more you do yourself, the more you learn.

The fuel filter is VERY easy.

On yours, look at your rubber fuel line on front of carb. See the clamp closest to the carb... Loosen it up, pull rubber line off, see the place that looks sort of brown on the carb in your picture right past the rubber fuel line.. Big nut there. Loosen that up and unscrew it. Fuel filter and a spring will be in that hole.

Pull out by hand, place new one in, screw big nut back tight, slip rubber line back on, tighten clamp.

 

Okay I'll do this asap. And what do you think this will help with exactly again?

 

There is also a link here on the site, if they got it fixed, that shows you how to tune it, specifically the "bogging" portion of it.

The fuel filter in the inlet of the carb is a weak link on the fuel delivery. If it's plugged up, you'll get less flow to the carb and thus less gas to run the motor. THis can make it feel "weak" when you step on it.

 

This was a big help I'll get this fuel filter replaced and let you
Guys know if it's better or not! Thanks for the advice!

 

If there's any other advice on what else could be the problems
Please let me know people thanks!

 

Your welcome... Always start out with the cheap, easy things 1st. Like Ozz said the Qjet fuel filter is a weak link. They are really small for a fuel filter and can clog up easy. If it gets clogged up you have less fuel to engine. Like ozz said.

With a dirty fuel filter it may idle fine and run ok at slower speeds, but step up on and it just noses over or lacks any real 'get up and go' due to engine not being able to get enough fuel

 

The sec air valve is held closed by the choke pull off. There is a spring that opens it that is adjustable and if the spring breaks they will not open. The manifold vacuum holds the valve closed with the choke pull off and when vacuum drops the spring over rides the diaphragm and forces them open. The speed at which they open is determined my spring pressure and the diameter of the hole in the choke pull off. I have had to replace the spring before. You can probably buy them but I pulled mine form a used carburetor last time I had this problem. On your sec air valve you will see a what looks like an adjustment screw that requires a flat head screw driver that is held with an allen set screw. You have to loosen the set screw to adjust the spring tension. It is possible that it just got loose and needs re adjusted. I don't remember how much tension that is recommended off the top of my head. I believe once you feel some tension from the spring that you turn it 3/4 turn and tighten the set screw as a starting point but it has been a few years so I don't remember for sure. A quick internet search will probably tell ya.

 

The tension you want is finger tight on the air flaps/valves. It should open freely with the touch of a finger but not flop open and stay open. It should spring back closed after you push down on it.

What happens is when you gun it from a stop, the air valve flops open flooding the carb with air, leaning out the mixture and causing the bog down. It can be a bit of work to get it to adjust right. Make sure you use the allen screw to loosen the assembly or you risk breaking/damaging the spring.

Ultimately, I'd recommend getting an external fuel filter and completely pulling and removing the fuel filter from the inlet of the carb. I had to do this on mine because I just would lose power at 4000+rpms and act like it was starving for fuel.

 

Ok, I also have to ask this.

When you turn the key to "run", does the carb "click"? It should start clicking and keep clicking for about thirty seconds to a minute. does it do this? If it does, the MCS is working correctly so lets start there.

 

Yes it does click, and would changing the fuel filter get rid of the check engine light? It's on cause of the carb problem we know that much.

 

What's the code? Have you pulled it yet? Do the paperclip method. Do a search for it here on the boards and it'll show you what to do.

It may not be for the carb depending on the code.

 

13-21-45 we took care of the O2 sensor and well I know it's something to do with the carb.

 

13 and 45 are o2 sensor faults. 13 is 02 sensor circuit and 45 is a rich condition.

21 is tps.

So yeah, almost all carb. Good call.


Looks like you need a new tps and need to tune the carb. Possibly tps only needs adjustment.

 

Tuning the carb ima have to take it to a mechanic cause my father and girlfriends father cannot do it sadly and I'll let them know to turn the tips thanks man

 

Most mechanics don't know how to tune a qjet anymore. Your best bet might be to get a book and lean to do it your self. That's what I've had to do.

 

It's getting really hard to find shops and mechanics that can truly rebuild, tune, mod carbs, HEI dist, set a timing curve, set dwell (points ign. system.

Got to keep in mind no car since the mid to late 80's have came stock with a carb.. Almost 30 years ago.

Look hard and long for a true carb tuner or read up on it, get a few books, etc and learn to do it yourself. Don't just trust any ole shop that says "sure we can do that"

 

Oops, ya Ozz is right the spring holds it shut and the choke pull off opens it. My bad been a few years sense my last Q jet. I use the have an SA design book on Q jets that was awesome. I think I got it from barns and noble. That is how I figured out how to fix my sec problem last time. I still have it around hears some were. It would be very handy if your working on your carburetor. I think I paid around $25 for it.

 

Replacing the fuel filter now but it doesn't look that bad at all. Why would my 83 firebird have a throttle position switch when it's not even throttle body?

 

You have an Electronically Controlled Carburetor that came standard on these cars from 82 to around 87 on some models. It's the step between old carbs and fuel injection/Throttle body.

The idle and WOT settings are set manually, however the carb, with input from the ECM via the O2 sensor, regulates the fuel flow at part throttle through a mixture control solenoid and throttle position sensor.

If you look at the top of your carb. The blue-green connector on the top of the passenger side of the carb is for the mixture control solenoid. Remember when I asked if your carb was clicking? That's this thing.

The white three-pin connector on the front drivers side of your carb is for the throttle possition sensor.

 

Well I got done replacing the fuel filter. Don't think it did much the light is still on. Found where the throttle position switch is located and we unplugged it while the car is idling in park and it nothing changed at all it idled te same and everything taking out and plugging it back in. So is that an idication that the tps is not working anymore?

 

The fuel filter will have little to no noticeable effect at idle. You won't notice is until you start pushing the motor while driving it.

The TPS has nearly zero effect when at idle.

It works like this. You drive along, the 02 sensor reads the emissions coming out of the motor and sends a signal to the ECM as to if the car is running rich or lean. the ECM then sends a signal to the Mixture control solenoid to either lean out or make the charge richer with fuel. But, it only does this when you are on the throttle, so it needs the reading from the throttle position sensor to know when to do this. Hence it only does it at "part throttle". Not Full throttle and not at "no throttle".


There are several threads on the site here that detail how to tune the carb if you wish to do it. It may also need a rebuild. It is 31 years old after all.

My guess it this. the code 45 is your car telling you that it's running rich. This could be from many sources.

1. the carb is simply out of tune and needs to be tuned up for the correct lean/rich mixture.
2. the plug wells on the bottom of the carb have started leaking and dripping fuel into the intake causing a rich condition. This means you need to rebuild the carb.
3. Another part of the carb is leaking internally and you're getting too much fuel in the charge. This also means the carb needs to be rebuilt.

The 21 is a TPS fault. Most likely, this means your TPS needs to be replaced. This takes 30 min tops if you do it yourself.

Code 13 is the o2 sensor circuit. Not sure, but normally this means you have a bad o2 sensor.

did you replace the o2 sensor yet? It's one plug on the harness and you can get to it physically by jacking the front of the car up. 30 min tops to replace. Just make sure you have the o2 sensor socket piece or you can bugger up the wire on it. A wrench might also work if you can get it to fit in there.

 

Yes I replaced the O2 sensor. I'll get the carb tuned I already planned on doing that. And okay well then the throttle switch is hard to tell if it needs to be replaced but if the code is popping up then I guess I'll just replace that too.

 

I'm getting the carb tuned on Thursday. How bad is a 305 v8 on gas though cause I'm putting in so much for gas it's like not normal. I had my car filled up on premium two days ago. Drove like 10 miles and back to my college and then 15 miles to my girlfriends today and I'm already at half a tank. That's not normal right??

 

No, that's not normal. My 84 L69, 305 with cc qjet got 23 highway and 16 city.

Since I swapped in my 355, also with the occ qjet, i get 19 highway and 12 city.


I dont want to sy a tune wont work bit I'll bet you have leaky plug wells. Try tuning it, but I'm not sure that is going to fix it.

 

Well when they tune the carb they would be able to see if there's a leak of something right? If it needs to get rebuilt how much would that be exactly?

 

If he's worth anything, he should notice it when it won't tune properly.


The plug wells are on the bottom of the carb and leak fuel directly onto the motor causing an nearl untuneableb rich condition signified by horrible gas mileage. Also you can't see this leak unless he pulls the carb off of the car.

As for a rebuild, there are three shops I would trust and each is going to run $350+ and then it would only come withba roughbtune and still need a fine tune once on the car.

 

Well if it's just fixing those on the bottom of the carb and nothing else is leaking could it be worth fixing the problem myself? I might as well get a new carb if I'm gonna spend that much to rebuild it.

 

Its definitely worth trying if the tune doesn't hold.

Also, rebuilding it will basically make it new, so no need to buy a new one.

Mine was rebuilt by cliff ruggles at www.cliffshighperformance.com

He also sells all the parts you can possibly need and is willing to talk on the phone about it.

Up to you how you want to go from here. I'd start with the tune attempt and go from there.

 

Id also PM NAF and Aperion here, they might be able to offer more insight to this issue.

 

Okay so got the carb tuned and adjusted which helped a lot! No leaks or anything however they said I need to replace the purge valve which will cost like 135 bucks for them to do it. Is it easy enough to do it myself of should I let them do it? The check engine light is still on maybe cause it's still running a tiny bit rich? They said its 75% done and only need to do the valve to make it perfect. So I'm guessing it's just purge valve that's keeping the light on or maybe the tps? But they wouldn't be able to tune the carb correctly if the tps wasn't working like you guys said earlier so I'm a bit confused as to why this light is still on