Driving the chevelle today and gave it a little gas (ok more than a little:D ) then I let off. After a little bit I returned my foot into it to drive at normal speed, but it began sputtering, like the car was running out of gas.

It definitely has gas in the fuel tank. Now to limp it home, I had to keep the rpm's up (2500 +) and ease the throttle when speeding up. Taking off from a stoplight almost killed it. I had to really ease into the throttle.

Did I do something to the carb (quadrajet ) or am I getting vapor lock (90 degrees outside)?

Any ideas?

Check your fuel filter.

Look for a big vacuum leak--hose to the brake booster, the check valve at the booster, any other vacuum hoses that may have blown off.

BillL

Some thoughts ... Sometimes you may get a little piece of trash in fuel and it can cause needle valve not to seat properly and close fuel inlet ... , or fuel pressure can be overcoming float ... I suspect that by feathering the throttle, you are actually allowing enough air in to prevent car from choking out ... are you seeing any black smoke. ... when you first depress throttle, the accelerator pump is being engaged and giving a squirt of fuel ... the "light" touch is minimizing the squirt... As stated before, check fuel filter and vacuum leaks ... Then look at carb ... Also, if a float is sticking, sometime you can give it a gentle rap-a-tap and the float will unstick ...

Been away from the car a while, so back to this subject.

It doesn't seem to have any vacuum leaks, and I have cleaned the filter.

Another thing I forgot to mention, after the car sits for a few days, it seems like the fuel bowl is empty. When I go to start the car, it takes 5-10 seconds to start, due to lack of fuel (mechanical fuel pump).

One more thing I just discovered. I have never worked on the fuel system, up until now. I just discovered that the 2 of the 4 carb mounting bolts are missing. The back ones (toward the firewall) are there, but the front two are gone.:clonk:Would this have much effect on performance?.... I will get those in there before continuing, or starting the car.

yeah, missing carb bolts could cause a huge vacuum leak if it is sucking in air under the base of the carb. could also warp the carb base i would think.

O.K. I put bolts in the front of the carb., rechecked vacuum lines, ect.

I started the car, and had to feather the throttle, just like when the problem started. If you give the car a quick, hard tap on the throttle (in park) it sputters, and backfires.

With the car off, I looked down the carb to see if it was shooting gas when I opened the throttle. It did, so the booster must work.

Do you think my distributor moved? Or timing chain crapped out?

The car would idle, in park, slightly warmed up. You can slowly give it gas, and it will go thru the entire rpm range. Its just if you give it too much gas, too quick, it will backfire, with a loud pop (more like thru the exhaust?). IE, sounds like when you turn off the ignition, give it a squirt of fuel, and turn the ignition back on.

Check the choke and choke pull off. If your squirter is working, then you can probably rule out accelerator pump. But if the choke is off when you need it or in when you don't you'll have drivability issues.

When the engine is warming up the choke should be partially closed, the choke pull off (little plastic vacuum can on the passenger side) should pull open the choke when you hit the throttle. If not, you could be rich when trying to accelerate.

I had a situation once where the choke was stuck about half open. The car would run at speed, but was really rough and rich coming off the line. I had to get it above about 2000 RPM, which got the secondaries open to add additional air.

Update:


Started the chevelle this morning to try to get to the root of this problem.

It started and idled fine. So I get a timing light on it, and it's 14 degrees advanced, so it seems OK. I give the throttle a rap, no problems???:confused:

So I go to test drive it, and the problem went away????:confused:

Only thing I can think of is there must have been something between the needle and seat. Does this sound right to you?

Thanks for all the advice!!:beers:

Pat

Pull your dist cap off and by hand rotate the motor (either direction) and make sure the rotor moves, then stop, put a mark anywhere on the balancer and then watch the rotor, and move the crank slowly by hand in the opposite direction and stop as soon as the rotor moves. check and see how much distance the crank moved. That is now much slop you have in your chain.
With the factory quiet cam gear (plastic/fiber teeth) it will tell you that your losing the teeth by how much it moves. metal gears won't show as much movement, and tell how loose the chain is. I have never lost a metal cam gear and chain. Now the factory "Quiet" gears, I have lost a few motors to those!

Pat

SCRATCH MY LAST POST!!!!:mad:

Started up the car again, runs like shi*!! Back to the way it was in my first post!!!:mad:

WTF is going on here????

have you checked out the power valve in your carb? i had a backfire through the carb once due to wiring the firing order wrong. close but wrong. it started but backfired through the carb a couple times. power valve was blown from the backfire. it acted like what you are describing. new powervalve fixed it. in fact it ran better since i put a more correctly calibrated power valve in while i was at it.

Enrichment on a Q-jet is with metering rods, not a power valve.

Proform, are you running too rich or too lean? Backfire out the tail pipes sounds like you're rich. But if you're chasing vacuum leaks (e.g. missing carb bolts) then you're lean. A lean miss will backfire out the carburetor, you didn't mention this in your post, but is this what you have? Pull a couple of spark plugs, what do they look like?

An intermittent problem may be electrical related. Do visual and wiggle test of the primary wires to the coil and distributor. Do you have points of electronic?

Threw a new carb on (Edlebrock). Same exact problem:mad: . It doesn't put out black smoke, and seems like it idles ok, but if I give it a moderate amount of throttle, it misfires(chugs?) and will want to backfire (sometimes out the exhaust, sometimes through the carb.

I have a point style distributor, and it is set at 14 deg. initial, and is advancing with rpm.

Any more thoughts?

Pat

I think you've got an ignition problem. Before going further down the ignition path though, verify you have sufficient fuel pressure when you try to accelerate the motor. Edelbrocks like no more that 5.5 psi, you need a minimum of about 4 psi. It's the only fuel related thing I can think of that would affect both carburetors.

Back to the ignition. As you accelerate the engine, the cylinder pressure starts to increase, making it "harder" for the ignition system to jump a spark across the spark plug gap. So, if part of this system is weak, as you require it to work harder, so the motor starts to "break up" and run rough.

Start with a visual inspection, look for corrosion at the wire terminals to the coil, and that these wires are good condition. Sounds basic, these are 40 years old. (I had a no-fire condition once and it turned out that one of my ignition wires was corroded right at the terminal to the point were only a few strands were intact.)

Inspect the distributor cap and rotor. If the electrodes are worn, replace them. If there is a lot of carbon tracking, replace them. The carbon tracks can actually divert high voltage spark to ground instead of the plugs. Check you distributor springs and weights while the rotor is off. Make sure that they are free to move. You did say your timing is advancing in the last post so they're probably okay, but do a visual as long as you've got the cap off.

Next, it's probably worth replacing points and condenser. Don't overlook the condenser, these can fail with age and heat and can really impact the coil's ability to charge, especially at higher engine speeds. With new points, you need to set the dwell (gap) and then reset the timing.

Check your spark plug wires too. A good test is to mist with water from a spray bottle in a dark garage. If the insulation is failing, the electricity will arc out of the wires when they are wet -- look for blue sparks. Pay special attention to the coil wire. This is the first wire the spark has to travel though on it's way to the plugs.

Check for a strong spark. A strong spark will appear sharp and blue, a weak one will look yellow or orange. You can do this by pulling a wire off a plug and hold it close the plug's electrode, watching for the spark to jump from the wire to the plug. Alternatively, pull out the plug, reconnect the wire, and lay the plug on an good metal ground (away from fuel sources) and watch for spark. Rev your engine to recreate the symptom and watch for spark. If it's weak, be suspicious of the coil or coil wire.

Enrichment on a Q-jet is with metering rods, not a power valve.

Proform, are you running too rich or too lean? Backfire out the tail pipes sounds like you're rich. But if you're chasing vacuum leaks (e.g. missing carb bolts) then you're lean. A lean miss will backfire out the carburetor, you didn't mention this in your post, but is this what you have? Pull a couple of spark plugs, what do they look like?

An intermittent problem may be electrical related. Do visual and wiggle test of the primary wires to the coil and distributor. Do you have points of electronic?
oops, guess it would help if i read the whole thread huh? duh, sorry bout that. knowing that, i would have to agree that it sounds like an electrical prob. check out the coil (had one short out once and did that) also check all connections and might as well change points and condensor.

Had the same problem, under the same conditions, with an old Blazer years ago. I raced another Blazer down the road, as I slowed the engine sounded like it grenaded. Woke the entire nieghborhood. I couldn't start the thing and had it towed home, with my ego. Turned out the points had closed.

Got it fixed!!!:thumbsup:
Changed out the distributor. I had a point system, and decided to throw a HEI distributor in it. Seems to work OK now!!!

Thanks for the replies!!!:beers: