Looking for info on the feedback carb systems

[usetaboost]

Bought the wife a 85 el camino with a 305. It runs pretty good but just wanted to go through and check things out when I get around to doing a tune up. I'm not talking about doing a tear down or anything but just want to find out what common problems are with these and how to check out all the components of the carb setup and the vacuum ports in the intake. I noticed that it seems to idle kind of high, around 1k. Thanks

...and of course its gotta have that gay 200c trans. Just gonna wait for it to die then the monte ss trans is going in!

 

[charlief1]

If you've still got my number call me late (1700- 1900 CST) tomorrow Jesse. If not send me an email and I think I can help you out.

 

[usetaboost]

Just send me a pm or post the info here. I don't check my email much

 

[usetaboost]

If you've still got my number call me late (1700- 1900 CST) tomorrow Jesse. If not send me an email and I think I can help you out.

Charles, after doing some thinking I'm willing to give it another shot with this carb on the el camino. Do you know of any links that have some good pics and info on checking stuff on the carb? It's gotta be something easy. The only problem I have with it at this point is the miss at 800-850. If it's in gear and I hold it at this rpm while taking off it spits and sputters a bit. It only does it on a light take off or at a crawl. If I can get this problem fixed I plan on doing a lot more to the car engine wise. Nothing crazy, just exhaust, intake, dual snorkle air cleaner, maybe a cam if I got a lot of time on my hands and an extra 200 bucks.

 

[charlief1]

Charles, after doing some thinking I'm willing to give it another shot with this carb on the el camino. Do you know of any links that have some good pics and info on checking stuff on the carb? It's gotta be something easy. The only problem I have with it at this point is the miss at 800-850. If it's in gear and I hold it at this rpm while taking off it spits and sputters a bit. It only does it on a light take off or at a crawl. If I can get this problem fixed I plan on doing a lot more to the car engine wise. Nothing crazy, just exhaust, intake, dual snorkle air cleaner, maybe a cam if I got a lot of time on my hands and an extra 200 bucks.

Might want to go to the 301garage Jesse. Joe's got some good info on how a Q-jet works and I've been feeling in the blanks for him. Most of the time it's an off idle issue that has to do with the off idle circuit (slots just above the mixture screws) being blocked or restricted. Do you have the tools to overhaul it completely Jesse?

 

[usetaboost]

Might want to go to the 301garage Jesse. Joe's got some good info on how a Q-jet works and I've been feeling in the blanks for him. Most of the time it's an off idle issue that has to do with the off idle circuit (slots just above the mixture screws) being blocked or restricted. Do you have the tools to overhaul it completely Jesse?

Yeah someone else mentioned that also. I did back the tps down to .46 volts which is pretty close to where it needs to be. The stumble seemed to go away slightly and it does keep the converter from locking up right away in 3rd so that's definitely better. Here's a thought, even though my idle rpm's are dead on, do you think I could have a intake or carb base leak causing this issue?

I have no carb tools but I did learn something. You can tear apart an old pen and use the plastic tube to turn the adjustment for the tps and whatever else it would happen to slip over. Everyone makes fun of me for being cheap but hell, it worked and saved me some time and money that's for sure

 

[charlief1]

There's more to it than the TPS Jesse. If you do a search for Thexton on evilbay you might find the right tools to set everything up fairly resonably. I would check all the vaccum lines and replace the base gasket just to make sure you don't have a leak. There's a lot of things you can do to get more out of the carb but you really need to do some reading and research on what you want to do. If you want to make it simple get rid of the electronics and set it up with a regular carb and distributor.

 

[usetaboost]

As for right now I just want to learn the basics down just get it it running the way it should. I'd like to keep the feedback carb for mpg reasons. I have been reading on these carbs and they seem to be the way to go if you aren't building something for the drag strip and don't plan on much more than a mild build, so it sounds perfect for what my plans are with the car. There's no service light on and no starting problems so it has to be something small. Tomorrow I will run up and get a can of brake clean and start spraying the intake and carb base and try to find a leak. It looks like the intake is leaking oil in the front so that could very well be what the problem is. If I don't find a leak I'm going to get a dwell meter and check the MC solenoid. It would be nice to get this problem fixed so I can concentrate on other areas of the car.

 

[usetaboost]

I can go out there right now with it dead cold and start it just as how it should be started and immediately drop it in drive and not have one stumble, but as soon as it gets up to temp and settles down is when it does it. Makes me wonder if it's something in the closed loop system since the carb works like a normal carb while in open loop and under WOT conditions right? So, I know the idle is set where it needs to be, tps is ruled out, tuneup parts and fuel filter ruled out, no rotted vac lines, no timing issue, engine hasn't been abused, no SES light, new denso 02. If it's not a manifold or baseplate leak, it's gotta be a m/c solenoid issue, right?

I've been snooping around the 301 forum, haven't found anything vital yet. Lots of lg4 info on the thirdgen.org site but responses are far and few between which kinda pisses me off.

 

[charlief1]

One thing I will warn you about is the large line off the top of the carb. Can't remember what the valve it goes to is called but there's 3 or 4 vac lines running to it. One large one from the top front of the carb and one large one at the bottom front and 2 (I think) for vac source. If the valve goes bad it will suck gas out of the carb and you'll run rich. Fairly common issue off idle. Easiest way to check is to go for a quick drive above 50 MPH and when you stop pull the line off the top front of the carb and you'll see either gas in it or have a very strong gas smell in the line or valve.

 

[usetaboost]

I've read what you are talking about, just can't remember exactly what it was. Come to think of it, I have noticed a fuel smell under the hood after it's been ran for a while when I was messing with it.

 

[charlief1]

It should have a part number stamped on it and you can cross it to find out what it is. That might also be causing the slight bog since it's a vacuum loss.

 

[usetaboost]

I'll look into it if I have time today. Believe it or not I just took the headliner board out without removing the front and rear trim strips

 

[usetaboost]

Pulled the cap and rotor on the car last night and it was full of white dust and the cap was looking kind of crusty underneath so I replaced that, the rotor, and pulled the module and put a layer of fresh grease on it. The cap and rotor were original so I don't feel I wasted any money there. The car seemed to rev a little faster after that but still no change. I DID find that the front vacuum break were bad on BOTH carbs I had so I robbed it off another carb I had around. Doesn't seem to run pig rich anymore on cold start and it will idle down once it gets warmed up. Still has a very slight stumble when it's warm off idle. Lazy 02? idle screws need adjusted? I might pull a few plugs tomorrow and see if they are fouled.