Hey everyone, I have a 460 that is basically stock and has a HOLLEY 4 barrel carb, not sure if this is stock or not. Anyways she fires up and idles great, starts out at about 1000rpms, then when you tap the gas the idle drops to about 550rpms. MIght need to adjust the idle a bit but its not bad. Anyways when you give it a lot of gas it wants to die out, if you give it gas slowly its fine. Happens whether I am driving or just idling. At first we thought the timing may have been off, I checked it today and my timing is currently at 12 degrees.


Not sure how many miles are on this motor but its looking a little tired, the seals are all starting to leak, the motor is damp everywhere with oil. I just replaced the distributor cap and rotor, as well as the plugs. Any one have any idea why it woudl miss like this with sudden throttle?

 

The dropping idle sounds normal, it sounds like the choke is opening up normally. The accelerator pump could be misadjusted, plugged, or the main jets could be plugged. You could also have a vacuum leak. I think the question would be better answered in the fuel forum.

 

I know the vacuum should be fine, can't seem to find any leaks, but I will try the fuel forum thanks.

 

Hello, I seem to be having a similar problem but I dont have a truck I have a 1979 Mark V, 400 engine. When it starts up *COLD* it idles high maybe about 1500+rpm. When I put it in gear the thing wants to just bolt out of my garage, it accelerates out of my neighboor hood on its own... until I touch the gas. Once I touch the gas the thing seems like it drops to 500 rpm. It makes a wierd almost guzzling noise when I put the gas on. I just had the carb rebuilt (twice), the fuel pump fixed, some vacuum/choke lines replaced and a new eqr + gasket between eqr and intake replaced. The car used to knock at medium to high throttle. Now it does not knock when I accelerate anymore except for maybe a faint knocking. If I put it in DRIVE, and put the brake on and then start to hit the throttle it will start knocking mid way through. It sounds like a pinging from timing almost, but timing was checked twice aswell. When I accelrate the car has a "lag" where there is no acceleration at very little throttle, then it kicks in past a certain point and starts accelerating.

Basically, the shop I go to is lost but they do warrenty their work so they will keep working on my car. It just seems like everytime I give it to them something else gets messed up. If you guys have any suggestions of what I should tell them to look for so I can finally get my car working smoothly again.

Any help would be great.

Thanks guys
-Urbel

 

Do you have the fast idle solenoid on your carb? Anyway, fast idle can be adjusted by either turning the screw on the idle sol. or on passenger side of carb at the bottom. Just follow the linkage and you can see it.

 

I got rid of knocking, I noticed a lot of carbon build up, so I realized it was most likely intake manifold cuasing a pre-ignition spark, running 89-90 octane and a can of seafoam through the gas tank for 5-6 tanks full has cleared up the knocking completely.

when car is cold I still get a "lag" and a "guzzling" noise when pressing the gas until the car warms up (5-15 minutes) then it goes away.

When its hot the carb floods but only after its been used for 1 hour + and sits for 20+ mins.

Dealership still cant figure out and has refused working anymore and wont honor their warranty so I am still searching for the answer.

The car idles really high when its cold until I touch the gas then idle drops low.

If anyone has any idea what is cuasing a lag, guzzling, funny idling let me know. I have a feeling they are all related. It could be as simple as carb tuning, but float and pin/needle they keep saying is fine..

Let me know what you guys think.

Thanks
-UrbelT

 

The fast idle will not lower upon start up until two things happen. First, the engine has to be warm and second, you have to press the accelerator down and release it really fast, then it will idle down.
From the sound of it, I would check all the plugs, caps, etc. that have been put on there to stop vacuum leaks. It sounds like you have a leak around somewere to me. It's not to much just to change them all out with new ones just to make sure.