Bouncing at idle?

I adjusted the timing at my work today, i notice the engine has slightly more power now when i step on the gas but if im sitting at a red light or have it in park the car feels like its bouncing, it was doing this before the timing was adjusted too, im thinkin a misfire? the plugs, wires and dist cap are about a year and a half old.

Check your idle speed - should be in the area of 600 RPM idle, in gear.

yeah i was gonne chack that first, is it best to adjust the idle when the engine is cold and the carb is running at fast idle or after its warmed up and the idle kicks down?

yeah i was gonne chack that first, is it best to adjust the idle when the engine is cold and the carb is running at fast idle or after its warmed up and the idle kicks down?

Fully heated to operating temperature.

k thought so

I just got my car back today, the guy said i had a bad TPS sensor which he said was causing my idle to change up and down randomly. So this could be related to your problem also.

Ill have to check that out

Ill have to check that out

I'm pretty sure the TPS is buried in teh carb and requires you to take it apart in order to get at it.

I just got my car back today, the guy said i had a bad TPS sensor which he said was causing my idle to change up and down randomly. So this could be related to your problem also.

He fed you a line of bull if that is indeed the case. The TPS on the carbureted car is used in conjunction with other sensors to allow the computer to determine engine load at a given RPM. Fuel flow through the carburetor is controlled in two areas (both rely on vacuum) - the venturi draws gasoline from the bowl through the jets (metering jets) whenever the throttle is part open to completely open. The other thing is the idle circuit, which controls fuel flow when the throttle is closed.

There is a possibility that the idle air bleed in the carburetor is improperly adjusted and this can cause this issue. The idle air bleed controls the idle fuel flow on these feedback carbs by allowing a certain amount of air to be drawn with the gasoline (effectively metering the fuel) and this can be controlled by the mixture control solenoid (which is driven by the computer). Again, either of this gets back to a carburetor issue - exactly what I diagnosed your car to have.

The TPS is installed in the left front side of the carburetor (the carburetor left, when you look at it full on it's on the right), and has a 3-wire connector.

http://www.silicon212.org/qjetnotes.jpg

He fed you a line of bull if that is indeed the case. The TPS on the carbureted car is used in conjunction with other sensors to allow the computer to determine engine load at a given RPM. Fuel flow through the carburetor is controlled in two areas (both rely on vacuum) - the venturi draws gasoline from the bowl through the jets (metering jets) whenever the throttle is part open to completely open. The other thing is the idle circuit, which controls fuel flow when the throttle is closed.

There is a possibility that the idle air bleed in the carburetor is improperly adjusted and this can cause this issue. The idle air bleed controls the idle fuel flow on these feedback carbs by allowing a certain amount of air to be drawn with the gasoline (effectively metering the fuel) and this can be controlled by the mixture control solenoid (which is driven by the computer). Again, either of this gets back to a carburetor issue - exactly what I diagnosed your car to have.

The TPS is installed in the left front side of the carburetor (the carburetor left, when you look at it full on it's on the right), and has a 3-wire connector.

Now i'm confused. So a bad TPS can't cause the idle issue by itself? If its used in conjunction as you mentioned above then couldn't it screw up what all the other sensors do in response?

Now i'm confused. So a bad TPS can't cause the idle issue by itself? If its used in conjunction as you mentioned above then couldn't it screw up what all the other sensors do in response?

I am thinking that if you had that carb rebuilt, it wasn't adjusted properly. Someone didn't set the M/C solenoid. If it wasn't rebuilt, then that problem will show up again. The idle air bleed quite possibly was set too lean.

Did you ever have the MIL on and if so, did you ever pull the trouble codes?

fixed, some spark plugs were covered in carbon deposits, replaced all 8 of them

fixed, some spark plugs were covered in carbon deposits, replaced all 8 of them


how long did it take you to do that? i know the last plug on both sides can be a B*TCH... i talked to the guy who owned my car before me and in 150,000 miles he never gave it a tune up... damn. i plan on doing cap/rotor plugs and wires this weekend

I actually took it to get that done, i know spark plugs are easy but there was some other things i wanted checked out too, i figured since i was already there why not. the ones in the back they said on previous tune ups they (dis honest mechanics) sometimes leave the back two in

I actually took it to get that done, i know spark plugs are easy but there was some other things i wanted checked out too, i figured since i was already there why not. the ones in the back they said on previous tune ups they (dis honest mechanics) sometimes leave the back two in

its been a while since I experienced this and it turned out to be the ignition module...at about 10,000mi before it totally died my engine had this issue...after the replacement it was smooth....carb has never been rebuilt on my 84........305.......

how long did it take you to do that? i know the last plug on both sides can be a B*TCH... i talked to the guy who owned my car before me and in 150,000 miles he never gave it a tune up... damn. i plan on doing cap/rotor plugs and wires this weekend

Yeah the tune up is definately a must. It increases your gas mileage a little too! When i replaced my cap/ rotor i was surprised the car could even run. The inside components were all melted and chewed up for whatever reason.

outa curiosity, how do you adjust the timing?

outa curiosity, how do you adjust the timing?

With an inductive timing light and a distributor wrench. Disconnect the computer wires (the 'EST' cable - 4 wires) from the distributor and start the engine, with the transmission in park. Adjust your idle RPM to 800 or so while in park. With the inductive pickup on the #1 plug wire, aim the timing light at the timing tab. You might need to move some hoses out of the way while you do this BUT BE CAREFUL as you can lose a finger or more, should you accidentally touch a belt, pulley or the fan as the engine is running. Look at the VECI label on the radiator fan shroud - you want the timing to match that number. Aim the light at the tab and pull the trigger - you should see the mark on the harmonic balancer and it should be located at some point along the timing tab. On a carb engine, static timing should likely be somewhere between 6 and 8 degrees BTC. On an EFI engine, it should be 0.

If you need to adjust the timing, rotating the distributor clockwise will retard the timing, while rotating counter clockwise will advance it. The distributor rotates in a clockwise direction.

Once you have the timing adjusted, plug the EST cable back into the distributor and double check the idle speed. It should match what is on the VECI label. (VECI = Vehicle Emission Control Information).

Clockwise? From the top or the bottom? http://72.19.213.157/files/devil.gif

If your cooling system is up to specs and EGR is working properly, you should be able to get away with running a 305 with at least 6º of base timing advance, especially if you are using fuel with 10% ethanol. That can help you pick up a little mileage and a bit more power.

With an inductive timing light and a distributor wrench. Disconnect the computer wires (the 'EST' cable - 4 wires) from the distributor and start the engine, with the transmission in park. Adjust your idle RPM to 800 or so while in park. With the inductive pickup on the #1 plug wire, aim the timing light at the timing tab. You might need to move some hoses out of the way while you do this BUT BE CAREFUL as you can lose a finger or more, should you accidentally touch a belt, pulley or the fan as the engine is running. Look at the VECI label on the radiator fan shroud - you want the timing to match that number. Aim the light at the tab and pull the trigger - you should see the mark on the harmonic balancer and it should be located at some point along the timing tab. On a carb engine, static timing should likely be somewhere between 6 and 8 degrees BTC. On an EFI engine, it should be 0.

If you need to adjust the timing, rotating the distributor clockwise will retard the timing, while rotating counter clockwise will advance it. The distributor rotates in a clockwise direction.

Once you have the timing adjusted, plug the EST cable back into the distributor and double check the idle speed. It should match what is on the VECI label. (VECI = Vehicle Emission Control Information).


this is how I check the timing also ....mine is 7.5deg at 800rpm... carb..the only difference is,, I mark the 7.5 and the harmonic balancer with white chalk...this makes the check very accurate...and if I need to adjust loosen the distributor so that it will move with some resistance...


with todays fuels you may have to retard timing to 6 degrees...