So since its s beautiful day here in DFW, i decided to take the vette out for a little spin since its my day off. When i get up to the highway, i get on and accelerate slowly unitl i get to the speed limit...or a little over give or take a few mph. Since im going no where in particular, i turn get off the highway and turn back around to head home. Thats where the trouble starts.
Stupidly i decide to give the vette much more gas than normal just to see what its got. While im pressing on the gas kinda of aggressivly, the car begins to lurch over and over, kind of like a rocking motion, while accelerating. Usually is while it is approaching 2nd gear (Automatic 1975 stock tranny).
The motion is hard to explain, but i hope someone knows what im talking about. Car runs and drives PERFECTLY, just not when alot of gas pedal/my lead foot is applied to it. Tranny? engine? vaccuum? help!!

 

It sounds like you accelerate slowly. Carbs tend to be finicky with slow, even pressure. This is NOT fuel injection. It sounds like maybe your carb needs a little tuning in the secondary side. Glad to hear it runs good otherwise, and that your out for a ride with no place to go!

 

Sounds like a pinched or partially plugged fuel line or a clogged fuel filter. Basically, the carb is not providing enough fuel for the needs of the engine. It could be other things, but from your description, I'm thinking fuel supply problem.

 

i replaced the fuel filter not two months ago with the original type paper fuel filter. the fuel lines seem to be fine... Since it does not do this when i accelerate slowly, could that be the problem. also maybe a carb issue?

 

The symptoms are right for fuel starvation. It could also be a "weak" fuel pump. Runs alright with low fuel rate...bucks like a bronco when you up the volume.

 

if its an edelbrock carb you probably need to replace the metering rods and springs. the main squirt and accelerator pump. thats what solved my problem..but i still need to set the air/fuel installing a gas air flow gauge.but i would look at the carb and fuel starvation

 

my initial thought was the transmission giving out and the price tag that comes along with it. glad to hear that there is light at the end of the tunnel and could possibly not have to face a rebuild or replacment.
thanks for the advice 7T1vette
Oh and its a Q-jet if that makes any difference...
So are the fuel pumps cheap? easy to install? Saturday project hopefully?

 

Would chainging the fuel filter from a metal screen type one, to a paper type affect this in any way? just a thought

 

If you have replaced your fuel filter with an OEM style, it should provide enough filtered fuel to satisfy your engines demands. I vote for fuel starvation, from whatever cause, as the issue. By mashing the gas, you are asking for a lot of fuel that somehow can not be delivered. I would start at the tank and pull the rubber hose to see if it is in good shape. I would then disconnect the fuel line at the pump and blow low pressure air through the entire steel line to see if you have blockages. I would then hook up all of the lines and hoses and do a volume check of the pump. My 72 GM Service manual has a measurement for the amount of fuel that the pump should put out in a give time. (well, I THINK it does -CRS!) Don't forget a visual inspection of the fuel sock down in the tank.

Gary

 

try locking out the secondary air valve and see if it still happens

 

Changing the fuel pump is not a hard job....but, it can be tight to work on. There are only two bolts plus the fuel lines connected to the housing. Use smooth-jawed ViceGrip pliers or a clamp to shut off the rubber fuel supply line (without having to plug it) so that it can be removed from the pump. Also, DO NOT try to remove the fuel lines without using a second wrench to hold the fitting the line mates with; if you do you will damage the fitting or pump, and you probably won't get the fitting loose. Also use a fuel line wrench (if you have one). It is a 6-flat box wrench with a opening in one flat to fit over the fuel line. This will limit the risk of rounding-off the corners on the soft fuel line nuts. You can remove the pump pretty easily (once you can get a wrench on the bolts); but there is a pump rod which fits INSIDE the engine that transfers motion to the fuel pump. You need to rotate the engine so that the pump rod is in the UP position and NOT pushing down on the pump...in order to get the new pump assembled back more easily. Also, take the pump rod out and put some wheel bearing grease on it..so that it will stay up in position while you are installing the pump; otherwise it will keep wanting to fall out of its bore. Don't forget the engine block-to-fuel pump gasket...and you might want to put a little smear of Permatex sealant on both sides (so it will stick to the engine block and also seal better when installed). Again, this is not a hard job; but it has do be done a certain way to make the process go smoothly.

 

Sounds like carbon buildup blowing out of the engine.

BigBlockk

Later.....

 

Thanks guys for all the help. im glad that this seems not to be a trans problem. Ill defiantly look into all that you have said as soon as i have time.
I was thinking about it today, and remembered seeing the fuel line leading to the carberator had been "worked on by bubba" and part of the line was a rubber hose. is that right? why would someone change it out?

 

The fuel line from pump to carb SHOULD NOT BE RUBBER HOSE. I emphasized that, because doing so is very dangerous. If that hose melts from heat, cracks or gets hit by a rock and splits, the engine [and the plastic car] can go up in flames. That's why those lines are metal. Buy another fuel line for $20 or make your own if you've got the tools and know-how.

 

Ok, here is the deal. I can cruise all day ay 40, 60, or 80 mph. But as soon as I get a wild hair up my butt, and stomp on it, after about 5 seconds the engine starts couphing and sputtering like it is starving for fuel.

What are my steps to troubleshoot and correct this problem?

Thanks in advance!!

 

Either a clogged fuel filter, clogged pickup sock, kinked fuel line or the fuel pump is not delivering enough fuel.

 

im thinking that might be the source of the problem. even if its not it a good idea to get it fixed. Why would some one ever need to change that to a rubber hose might i ask?

 

heres a link to a thread about my problem which seems to be the same problem as you. its in the works
http://forums.corvetteforum.com/show...post1560158358

 

Cheap and quick. Bubba lives!

 

Pull the gas cap and take a peek at the sock in the tank. Its an easy fix but often overlooked. I did, that's why I now know...